PING [Patch][Middle-end]Add -fzero-call-used-regs=[skip|used-gpr|all-gpr|used|all]

Qing Zhao QING.ZHAO@ORACLE.COM
Mon Aug 3 15:42:51 GMT 2020


Hi, Uros,

Thanks a lot for your review on X86 parts.

Hi, Richard,

Could you please take a look at the middle-end part to see whether the rewritten addressed your previous concern?

Thanks a lot.

Qing


> On Jul 31, 2020, at 12:57 PM, Uros Bizjak <ubizjak@gmail.com> wrote:
> 
> 
> 22:05, tor., 28. jul. 2020 je oseba Qing Zhao <QING.ZHAO@oracle.com <mailto:QING.ZHAO@oracle.com>> napisala:
> >
> >
> > Richard and Uros,
> >
> > Could you please review the change that H.J and I rewrote based on your comments in the previous round of discussion?
> >
> > This patch is a nice security enhancement for GCC that has been requested by security people for quite some time.  
> >
> > Thanks a lot for your time.
> 
> I'll be away from the keyboard for the next week, but the patch needs a middle end approval first.
> 
> That said, x86 parts looks OK.
> 
> 

> Uros.
> > Qing
> >
> > > On Jul 14, 2020, at 9:45 AM, Qing Zhao via Gcc-patches <gcc-patches@gcc.gnu.org <mailto:gcc-patches@gcc.gnu.org>> wrote:
> > > 
> > > Hi, Gcc team,
> > > 
> > > This patch is a follow-up on the previous patch and corresponding discussion:
> > > https://gcc.gnu.org/pipermail/gcc-patches/2020-May/545101.html <https://gcc.gnu.org/pipermail/gcc-patches/2020-May/545101.html> <https://gcc.gnu.org/pipermail/gcc-patches/2020-May/545101.html <https://gcc.gnu.org/pipermail/gcc-patches/2020-May/545101.html>>
> > > 
> > > From the previous round of discussion, the major issues raised were:
> > > 
> > > A. should be rewritten by using regsets infrastructure.  
> > > B. Put the patch into middle-end instead of x86 backend. 
> > > 
> > > This new patch is rewritten based on the above 2 comments.  The major changes compared to the previous patch are:
> > > 
> > > 1. Change the names of the option and attribute from 
> > > -mzero-caller-saved-regs=[skip|used-gpr|all-gpr|used|all]  and zero_caller_saved_regs("skip|used-gpr|all-gpr||used|all”)
> > > to:
> > > -fzero-call-used-regs=[skip|used-gpr|all-gpr|used|all]   and  zero_call_used_regs("skip|used-gpr|all-gpr||used|all”) 
> > > Add the new option and  new attribute in general. 
> > > 2. The main code generation part is moved from i386 backend to middle-end;
> > > 3. Add 4 target-hooks;
> > > 4. Implement these 4 target-hooks on i386 backend. 
> > > 5. On a target that does not implement the target hook, issue error for the new option, issue warning for the new attribute.
> > > 
> > > The patch is as following:
> > > 
> > > [PATCH] Add -fzero-call-used-regs=[skip|used-gpr|all-gpr|used|all]
> > > command-line option and
> > > zero_call_used_regs("skip|used-gpr|all-gpr||used|all") function attribue:
> > > 
> > >  1. -fzero-call-used-regs=skip and zero_call_used_regs("skip")
> > > 
> > >  Don't zero call-used registers upon function return.
> > > 
> > >  2. -fzero-call-used-regs=used-gpr and zero_call_used_regs("used-gpr")
> > > 
> > >  Zero used call-used general purpose registers upon function return.
> > > 
> > >  3. -fzero-call-used-regs=all-gpr and zero_call_used_regs("all-gpr")
> > > 
> > >  Zero all call-used general purpose registers upon function return.
> > > 
> > >  4. -fzero-call-used-regs=used and zero_call_used_regs("used")
> > > 
> > >  Zero used call-used registers upon function return.
> > > 
> > >  5. -fzero-call-used-regs=all and zero_call_used_regs("all")
> > > 
> > >  Zero all call-used registers upon function return.
> > > 
> > > The feature is implemented in middle-end. But currently is only valid on X86.
> > > 
> > > Tested on x86-64 and aarch64 with bootstrapping GCC trunk, making
> > > -fzero-call-used-regs=used-gpr, -fzero-call-used-regs=all-gpr
> > > -fzero-call-used-regs=used, and -fzero-call-used-regs=all enabled
> > > by default on x86-64.
> > > 
> > > Please take a look and let me know any more comment?
> > > 
> > > thanks.
> > > 
> > > Qing
> > > 
> > > 
> > > ====================================
> > > 
> > > gcc/ChangeLog:
> > > 
> > > 2020-07-13  qing zhao  <qing.zhao@oracle.com <mailto:qing.zhao@oracle.com> <mailto:qing.zhao@oracle.com <mailto:qing.zhao@oracle.com>>>
> > > 2020-07-13  H.J. Lu <hjl.tools@gmail.com <mailto:hjl.tools@gmail.com> <mailto:hjl.tools@gmail.com <mailto:hjl.tools@gmail.com>>>
> > > 
> > >       * common.opt: Add new option -fzero-call-used-regs.
> > >       * config/i386/i386.c (ix86_zero_call_used_regno_p): New function.
> > >       (ix86_zero_call_used_regno_mode): Likewise.
> > >       (ix86_zero_all_vector_registers): Likewise.
> > >       (ix86_expand_prologue): Replace gen_prologue_use with
> > >       gen_pro_epilogue_use.
> > >       (TARGET_ZERO_CALL_USED_REGNO_P): Define.
> > >       (TARGET_ZERO_CALL_USED_REGNO_MODE): Define.
> > >       (TARGET_PRO_EPILOGUE_USE): Define.
> > >       (TARGET_ZERO_ALL_VECTOR_REGISTERS): Define.
> > >       * config/i386/i386.md: Replace UNSPECV_PROLOGUE_USE
> > >       with UNSPECV_PRO_EPILOGUE_USE.
> > >       * coretypes.h (enum zero_call_used_regs): New type.
> > >       * doc/extend.texi: Document the new zero_call_used_regs attribute.
> > >       * doc/invoke.texi: Document the new -fzero-call-used-regs option.
> > >       * doc/tm.texi: Regenerate.
> > >       * doc/tm.texi.in <http://tm.texi.in/> (TARGET_ZERO_CALL_USED_REGNO_P): New hook.
> > >       (TARGET_ZERO_CALL_USED_REGNO_MODE): Likewise.
> > >       (TARGET_PRO_EPILOGUE_USE): Likewise.
> > >       (TARGET_ZERO_ALL_VECTOR_REGISTERS): Likewise.
> > >       * function.c (is_live_reg_at_exit): New function.
> > >       (gen_call_used_regs_seq): Likewise.
> > >       (make_epilogue_seq): Call gen_call_used_regs_seq.
> > >       * function.h (is_live_reg_at_exit): Declare.
> > >       * target.def (zero_call_used_regno_p): New hook.
> > >       (zero_call_used_regno_mode): Likewise.
> > >       (pro_epilogue_use): Likewise.
> > >       (zero_all_vector_registers): Likewise.
> > >       * targhooks.c (default_zero_call_used_regno_p): New function.
> > >       (default_zero_call_used_regno_mode): Likewise.
> > >       * targhooks.h (default_zero_call_used_regno_p): Declare.
> > >       (default_zero_call_used_regno_mode): Declare.
> > >       * toplev.c (process_options): Issue errors when -fzero-call-used-regs
> > >       is used on targets that do not support it.
> > >       * tree-core.h (struct tree_decl_with_vis): New field 
> > >       zero_call_used_regs_type.
> > >       * tree.h (DECL_ZERO_CALL_USED_REGS): New macro.
> > > 
> > > gcc/c-family/ChangeLog:
> > > 
> > > 2020-07-13  qing zhao  <qing.zhao@oracle.com <mailto:qing.zhao@oracle.com> <mailto:qing.zhao@oracle.com <mailto:qing.zhao@oracle.com>>>
> > > 2020-07-13  H.J. Lu <hjl.tools@gmail.com <mailto:hjl.tools@gmail.com> <mailto:hjl.tools@gmail.com <mailto:hjl.tools@gmail.com>>>
> > > 
> > >       * c-attribs.c (c_common_attribute_table): Add new attribute
> > >       zero_call_used_regs.
> > >       (handle_zero_call_used_regs_attribute): New function.
> > > 
> > > gcc/c/ChangeLog:
> > > 
> > > 2020-07-13  qing zhao  <qing.zhao@oracle.com <mailto:qing.zhao@oracle.com> <mailto:qing.zhao@oracle.com <mailto:qing.zhao@oracle.com>>>
> > > 2020-07-13  H.J. Lu <hjl.tools@gmail.com <mailto:hjl.tools@gmail.com> <mailto:hjl.tools@gmail.com <mailto:hjl.tools@gmail.com>>>
> > > 
> > >       * c-decl.c (merge_decls): Merge zero_call_used_regs_type.
> > > 
> > > gcc/testsuite/ChangeLog:
> > > 
> > > 2020-07-13  qing zhao  <qing.zhao@oracle.com <mailto:qing.zhao@oracle.com> <mailto:qing.zhao@oracle.com <mailto:qing.zhao@oracle.com>>>
> > > 2020-07-13  H.J. Lu <hjl.tools@gmail.com <mailto:hjl.tools@gmail.com> <mailto:hjl.tools@gmail.com <mailto:hjl.tools@gmail.com>>>
> > > 
> > >       * c-c++-common/zero-scratch-regs-1.c: New test.
> > >       * c-c++-common/zero-scratch-regs-2.c: Likewise.
> > >       * gcc.target/i386/zero-scratch-regs-1.c: Likewise.
> > >       * gcc.target/i386/zero-scratch-regs-10.c: Likewise.
> > >       * gcc.target/i386/zero-scratch-regs-11.c: Likewise.
> > >       * gcc.target/i386/zero-scratch-regs-12.c: Likewise.
> > >       * gcc.target/i386/zero-scratch-regs-13.c: Likewise.
> > >       * gcc.target/i386/zero-scratch-regs-14.c: Likewise.
> > >       * gcc.target/i386/zero-scratch-regs-15.c: Likewise.
> > >       * gcc.target/i386/zero-scratch-regs-16.c: Likewise.
> > >       * gcc.target/i386/zero-scratch-regs-17.c: Likewise.
> > >       * gcc.target/i386/zero-scratch-regs-18.c: Likewise.
> > >       * gcc.target/i386/zero-scratch-regs-19.c: Likewise.
> > >       * gcc.target/i386/zero-scratch-regs-2.c: Likewise.
> > >       * gcc.target/i386/zero-scratch-regs-20.c: Likewise.
> > >       * gcc.target/i386/zero-scratch-regs-21.c: Likewise.
> > >       * gcc.target/i386/zero-scratch-regs-22.c: Likewise.
> > >       * gcc.target/i386/zero-scratch-regs-23.c: Likewise.
> > >       * gcc.target/i386/zero-scratch-regs-3.c: Likewise.
> > >       * gcc.target/i386/zero-scratch-regs-4.c: Likewise.
> > >       * gcc.target/i386/zero-scratch-regs-5.c: Likewise.
> > >       * gcc.target/i386/zero-scratch-regs-6.c: Likewise.
> > >       * gcc.target/i386/zero-scratch-regs-7.c: Likewise.
> > >       * gcc.target/i386/zero-scratch-regs-8.c: Likewise.
> > >       * gcc.target/i386/zero-scratch-regs-9.c: Likewise.
> > > 
> > > ---
> > > gcc/c-family/c-attribs.c                           |  68 ++++++++++
> > > gcc/c/c-decl.c                                     |   4 +
> > > gcc/common.opt                                     |  23 ++++
> > > gcc/config/i386/i386.c                             |  58 ++++++++-
> > > gcc/config/i386/i386.md                            |   6 +-
> > > gcc/coretypes.h                                    |  10 ++
> > > gcc/doc/extend.texi                                |  11 ++
> > > gcc/doc/invoke.texi                                |  13 +-
> > > gcc/doc/tm.texi                                    |  27 ++++
> > > gcc/doc/tm.texi.in <http://tm.texi.in/>                                 |   8 ++
> > > gcc/function.c                                     | 145 +++++++++++++++++++++
> > > gcc/function.h                                     |   2 +
> > > gcc/target.def                                     |  33 +++++
> > > gcc/targhooks.c                                    |  17 +++
> > > gcc/targhooks.h                                    |   3 +
> > > gcc/testsuite/c-c++-common/zero-scratch-regs-1.c   |   3 +
> > > gcc/testsuite/c-c++-common/zero-scratch-regs-2.c   |   4 +
> > > .../gcc.target/i386/zero-scratch-regs-1.c          |  12 ++
> > > .../gcc.target/i386/zero-scratch-regs-10.c         |  21 +++
> > > .../gcc.target/i386/zero-scratch-regs-11.c         |  39 ++++++
> > > .../gcc.target/i386/zero-scratch-regs-12.c         |  39 ++++++
> > > .../gcc.target/i386/zero-scratch-regs-13.c         |  21 +++
> > > .../gcc.target/i386/zero-scratch-regs-14.c         |  19 +++
> > > .../gcc.target/i386/zero-scratch-regs-15.c         |  14 ++
> > > .../gcc.target/i386/zero-scratch-regs-16.c         |  14 ++
> > > .../gcc.target/i386/zero-scratch-regs-17.c         |  13 ++
> > > .../gcc.target/i386/zero-scratch-regs-18.c         |  13 ++
> > > .../gcc.target/i386/zero-scratch-regs-19.c         |  12 ++
> > > .../gcc.target/i386/zero-scratch-regs-2.c          |  19 +++
> > > .../gcc.target/i386/zero-scratch-regs-20.c         |  23 ++++
> > > .../gcc.target/i386/zero-scratch-regs-21.c         |  14 ++
> > > .../gcc.target/i386/zero-scratch-regs-22.c         |  19 +++
> > > .../gcc.target/i386/zero-scratch-regs-23.c         |  19 +++
> > > .../gcc.target/i386/zero-scratch-regs-3.c          |  12 ++
> > > .../gcc.target/i386/zero-scratch-regs-4.c          |  14 ++
> > > .../gcc.target/i386/zero-scratch-regs-5.c          |  20 +++
> > > .../gcc.target/i386/zero-scratch-regs-6.c          |  14 ++
> > > .../gcc.target/i386/zero-scratch-regs-7.c          |  13 ++
> > > .../gcc.target/i386/zero-scratch-regs-8.c          |  19 +++
> > > .../gcc.target/i386/zero-scratch-regs-9.c          |  15 +++
> > > gcc/toplev.c                                       |   9 ++
> > > gcc/tree-core.h                                    |   6 +-
> > > gcc/tree.h                                         |   5 +
> > > 43 files changed, 866 insertions(+), 7 deletions(-)
> > > create mode 100644 gcc/testsuite/c-c++-common/zero-scratch-regs-1.c
> > > create mode 100644 gcc/testsuite/c-c++-common/zero-scratch-regs-2.c
> > > create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-1.c
> > > create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-10.c
> > > create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-11.c
> > > create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-12.c
> > > create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-13.c
> > > create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-14.c
> > > create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-15.c
> > > create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-16.c
> > > create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-17.c
> > > create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-18.c
> > > create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-19.c
> > > create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-2.c
> > > create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-20.c
> > > create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-21.c
> > > create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-22.c
> > > create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-23.c
> > > create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-3.c
> > > create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-4.c
> > > create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-5.c
> > > create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-6.c
> > > create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-7.c
> > > create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-8.c
> > > create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-9.c
> > > 
> > > diff --git a/gcc/c-family/c-attribs.c b/gcc/c-family/c-attribs.c
> > > index 3721483..cc93d6f 100644
> > > --- a/gcc/c-family/c-attribs.c
> > > +++ b/gcc/c-family/c-attribs.c
> > > @@ -136,6 +136,8 @@ static tree handle_target_clones_attribute (tree *, tree, tree, int, bool *);
> > > static tree handle_optimize_attribute (tree *, tree, tree, int, bool *);
> > > static tree ignore_attribute (tree *, tree, tree, int, bool *);
> > > static tree handle_no_split_stack_attribute (tree *, tree, tree, int, bool *);
> > > +static tree handle_zero_call_used_regs_attribute (tree *, tree, tree, int,
> > > +                                              bool *);
> > > static tree handle_fnspec_attribute (tree *, tree, tree, int, bool *);
> > > static tree handle_warn_unused_attribute (tree *, tree, tree, int, bool *);
> > > static tree handle_returns_nonnull_attribute (tree *, tree, tree, int, bool *);
> > > @@ -434,6 +436,9 @@ const struct attribute_spec c_common_attribute_table[] =
> > >                             ignore_attribute, NULL },
> > >  { "no_split_stack",        0, 0, true,  false, false, false,
> > >                             handle_no_split_stack_attribute, NULL },
> > > +  { "zero_call_used_regs",    1, 1, true, false, false, false,
> > > +                           handle_zero_call_used_regs_attribute, NULL },
> > > +
> > >  /* For internal use (marking of builtins and runtime functions) only.
> > >     The name contains space to prevent its usage in source code.  */
> > >  { "fn spec",               1, 1, false, true, true, false,
> > > @@ -4506,6 +4511,69 @@ handle_no_split_stack_attribute (tree *node, tree name,
> > >  return NULL_TREE;
> > > }
> > > 
> > > +/* Handle a "zero_call_used_regs" attribute; arguments as in
> > > +   struct attribute_spec.handler.  */
> > > +
> > > +static tree
> > > +handle_zero_call_used_regs_attribute (tree *node, tree name, tree args,
> > > +                                   int ARG_UNUSED (flags),
> > > +                                   bool *no_add_attris)
> > > +{
> > > +  tree decl = *node;
> > > +  tree id = TREE_VALUE (args);
> > > +  enum zero_call_used_regs zero_call_used_regs_type = zero_call_used_regs_unset;
> > > +
> > > +  if (TREE_CODE (decl) != FUNCTION_DECL)
> > > +    {
> > > +      error_at (DECL_SOURCE_LOCATION (decl),
> > > +             "%qE attribute applies only to functions", name);
> > > +      *no_add_attris = true;
> > > +      return NULL_TREE;
> > > +    }
> > > +  else if (DECL_INITIAL (decl))
> > > +    {
> > > +      error_at (DECL_SOURCE_LOCATION (decl),
> > > +             "cannot set %qE attribute after definition", name);
> > > +      *no_add_attris = true;
> > > +      return NULL_TREE;
> > > +    }
> > > +
> > > +  if (TREE_CODE (id) != STRING_CST)
> > > +    {
> > > +      error ("attribute %qE arguments not a string", name);
> > > +      *no_add_attris = true;
> > > +      return NULL_TREE;
> > > +    }
> > > +
> > > +  if (!targetm.calls.pro_epilogue_use)
> > > +    {
> > > +      warning (OPT_Wattributes, "%qE attribute directive ignored", name);
> > > +      return NULL_TREE;
> > > +    }
> > > +
> > > +  if (strcmp (TREE_STRING_POINTER (id), "skip") == 0)
> > > +    zero_call_used_regs_type = zero_call_used_regs_skip;
> > > +  else if (strcmp (TREE_STRING_POINTER (id), "used-gpr") == 0)
> > > +    zero_call_used_regs_type = zero_call_used_regs_used_gpr;
> > > +  else if (strcmp (TREE_STRING_POINTER (id), "all-gpr") == 0)
> > > +    zero_call_used_regs_type = zero_call_used_regs_all_gpr;
> > > +  else if (strcmp (TREE_STRING_POINTER (id), "used") == 0)
> > > +    zero_call_used_regs_type = zero_call_used_regs_used;
> > > +  else if (strcmp (TREE_STRING_POINTER (id), "all") == 0)
> > > +    zero_call_used_regs_type = zero_call_used_regs_all;
> > > +  else
> > > +    {
> > > +      error ("attribute %qE argument must be one of %qs, %qs, %qs, %qs, or %qs",
> > > +          name, "skip", "used-gpr", "all-gpr", "used", "all");
> > > +      *no_add_attris = true;
> > > +      return NULL_TREE;
> > > +    }
> > > +
> > > +  DECL_ZERO_CALL_USED_REGS (decl) = zero_call_used_regs_type;
> > > +
> > > +  return NULL_TREE;
> > > +}
> > > +
> > > /* Handle a "returns_nonnull" attribute; arguments as in
> > >   struct attribute_spec.handler.  */
> > > 
> > > diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
> > > index 81bd2ee..ded1880 100644
> > > --- a/gcc/c/c-decl.c
> > > +++ b/gcc/c/c-decl.c
> > > @@ -2681,6 +2681,10 @@ merge_decls (tree newdecl, tree olddecl, tree newtype, tree oldtype)
> > >         DECL_IS_NOVOPS (newdecl) |= DECL_IS_NOVOPS (olddecl);
> > >       }
> > > 
> > > +      /* Merge the zero_call_used_regs_type information.  */
> > > +      if (TREE_CODE (newdecl) == FUNCTION_DECL)
> > > +     DECL_ZERO_CALL_USED_REGS (newdecl) = DECL_ZERO_CALL_USED_REGS (olddecl);
> > > +
> > >      /* Merge the storage class information.  */
> > >      merge_weak (newdecl, olddecl);
> > > 
> > > diff --git a/gcc/common.opt b/gcc/common.opt
> > > index df8af36..19900f9 100644
> > > --- a/gcc/common.opt
> > > +++ b/gcc/common.opt
> > > @@ -3083,6 +3083,29 @@ fzero-initialized-in-bss
> > > Common Report Var(flag_zero_initialized_in_bss) Init(1)
> > > Put zero initialized data in the bss section.
> > > 
> > > +fzero-call-used-regs=
> > > +Common Report RejectNegative Joined Enum(zero_call_used_regs) Var(flag_zero_call_used_regs) Init(zero_call_used_regs_skip)
> > > +Clear call-used registers upon function return.
> > > +
> > > +Enum
> > > +Name(zero_call_used_regs) Type(enum zero_call_used_regs)
> > > +Known choices of clearing call-used registers upon function return (for use with the -fzero-call-used-regs= option):
> > > +
> > > +EnumValue
> > > +Enum(zero_call_used_regs) String(skip) Value(zero_call_used_regs_skip)
> > > +
> > > +EnumValue
> > > +Enum(zero_call_used_regs) String(used-gpr) Value(zero_call_used_regs_used_gpr)
> > > +
> > > +EnumValue
> > > +Enum(zero_call_used_regs) String(all-gpr) Value(zero_call_used_regs_all_gpr)
> > > +
> > > +EnumValue
> > > +Enum(zero_call_used_regs) String(used) Value(zero_call_used_regs_used)
> > > +
> > > +EnumValue
> > > +Enum(zero_call_used_regs) String(all) Value(zero_call_used_regs_all)
> > > +
> > > g
> > > Common Driver RejectNegative JoinedOrMissing
> > > Generate debug information in default format.
> > > diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> > > index 5c373c0..fd1aa9c 100644
> > > --- a/gcc/config/i386/i386.c
> > > +++ b/gcc/config/i386/i386.c
> > > @@ -3551,6 +3551,48 @@ ix86_function_value_regno_p (const unsigned int regno)
> > >  return false;
> > > }
> > > 
> > > +/* TARGET_ZERO_CALL_USED_REGNO_P.  */
> > > +
> > > +static bool
> > > +ix86_zero_call_used_regno_p (const unsigned int regno,
> > > +                          bool gpr_only)
> > > +{
> > > +  return GENERAL_REGNO_P (regno) || (!gpr_only && SSE_REGNO_P (regno));
> > > +}
> > > +
> > > +/* TARGET_ZERO_CALL_USED_REGNO_MODE.  */
> > > +
> > > +static machine_mode
> > > +ix86_zero_call_used_regno_mode (const unsigned int regno, machine_mode)
> > > +{
> > > +  /* NB: We only need to zero the lower 32 bits for integer registers
> > > +     and the lower 128 bits for vector registers since destination are
> > > +     zero-extended to the full register width.  */
> > > +  return GENERAL_REGNO_P (regno) ? SImode : V4SFmode;
> > > +}
> > > +
> > > +/* TARGET_ZERO_ALL_VECTOR_REGISTERS.  */
> > > +
> > > +static rtx
> > > +ix86_zero_all_vector_registers (bool used_only)
> > > +{
> > > +  if (!TARGET_AVX)
> > > +    return NULL;
> > > +
> > > +  for (unsigned int regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
> > > +    if ((IN_RANGE (regno, FIRST_SSE_REG, LAST_SSE_REG)
> > > +      || (TARGET_64BIT
> > > +          && (REX_SSE_REGNO_P (regno)
> > > +              || (TARGET_AVX512F && EXT_REX_SSE_REGNO_P (regno)))))
> > > +     && (!this_target_hard_regs->x_call_used_regs[regno]
> > > +         || fixed_regs[regno]
> > > +         || is_live_reg_at_exit (regno)
> > > +         || (used_only && !df_regs_ever_live_p (regno))))
> > > +      return NULL;
> > > +
> > > +  return gen_avx_vzeroall ();
> > > +}
> > > +
> > > /* Define how to find the value returned by a function.
> > >   VALTYPE is the data type of the value (as a tree).
> > >   If the precise function being called is known, FUNC is its FUNCTION_DECL;
> > > @@ -8513,7 +8555,7 @@ ix86_expand_prologue (void)
> > >      insn = emit_insn (gen_set_got (pic));
> > >      RTX_FRAME_RELATED_P (insn) = 1;
> > >      add_reg_note (insn, REG_CFA_FLUSH_QUEUE, NULL_RTX);
> > > -      emit_insn (gen_prologue_use (pic));
> > > +      emit_insn (gen_pro_epilogue_use (pic));
> > >      /* Deleting already emmitted SET_GOT if exist and allocated to
> > >        REAL_PIC_OFFSET_TABLE_REGNUM.  */
> > >      ix86_elim_entry_set_got (pic);
> > > @@ -8542,7 +8584,7 @@ ix86_expand_prologue (void)
> > >     Further, prevent alloca modifications to the stack pointer from being
> > >     combined with prologue modifications.  */
> > >  if (TARGET_SEH)
> > > -    emit_insn (gen_prologue_use (stack_pointer_rtx));
> > > +    emit_insn (gen_pro_epilogue_use (stack_pointer_rtx));
> > > }
> > > 
> > > /* Emit code to restore REG using a POP insn.  */
> > > @@ -23319,6 +23361,18 @@ ix86_run_selftests (void)
> > > #undef TARGET_FUNCTION_VALUE_REGNO_P
> > > #define TARGET_FUNCTION_VALUE_REGNO_P ix86_function_value_regno_p
> > > 
> > > +#undef TARGET_ZERO_CALL_USED_REGNO_P
> > > +#define TARGET_ZERO_CALL_USED_REGNO_P ix86_zero_call_used_regno_p
> > > +
> > > +#undef TARGET_ZERO_CALL_USED_REGNO_MODE
> > > +#define TARGET_ZERO_CALL_USED_REGNO_MODE ix86_zero_call_used_regno_mode
> > > +
> > > +#undef TARGET_PRO_EPILOGUE_USE
> > > +#define TARGET_PRO_EPILOGUE_USE gen_pro_epilogue_use
> > > +
> > > +#undef TARGET_ZERO_ALL_VECTOR_REGISTERS
> > > +#define TARGET_ZERO_ALL_VECTOR_REGISTERS ix86_zero_all_vector_registers
> > > +
> > > #undef TARGET_PROMOTE_FUNCTION_MODE
> > > #define TARGET_PROMOTE_FUNCTION_MODE ix86_promote_function_mode
> > > 
> > > diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
> > > index d0ecd9e..e7df59f 100644
> > > --- a/gcc/config/i386/i386.md
> > > +++ b/gcc/config/i386/i386.md
> > > @@ -194,7 +194,7 @@
> > >  UNSPECV_STACK_PROBE
> > >  UNSPECV_PROBE_STACK_RANGE
> > >  UNSPECV_ALIGN
> > > -  UNSPECV_PROLOGUE_USE
> > > +  UNSPECV_PRO_EPILOGUE_USE
> > >  UNSPECV_SPLIT_STACK_RETURN
> > >  UNSPECV_CLD
> > >  UNSPECV_NOPS
> > > @@ -13525,8 +13525,8 @@
> > > 
> > > ;; As USE insns aren't meaningful after reload, this is used instead
> > > ;; to prevent deleting instructions setting registers for PIC code
> > > -(define_insn "prologue_use"
> > > -  [(unspec_volatile [(match_operand 0)] UNSPECV_PROLOGUE_USE)]
> > > +(define_insn "pro_epilogue_use"
> > > +  [(unspec_volatile [(match_operand 0)] UNSPECV_PRO_EPILOGUE_USE)]
> > >  ""
> > >  ""
> > >  [(set_attr "length" "0")])
> > > diff --git a/gcc/coretypes.h b/gcc/coretypes.h
> > > index 6b6cfcd..e56d6ec 100644
> > > --- a/gcc/coretypes.h
> > > +++ b/gcc/coretypes.h
> > > @@ -418,6 +418,16 @@ enum symbol_visibility
> > >  VISIBILITY_INTERNAL
> > > };
> > > 
> > > +/* Zero call-used registers type.  */
> > > +enum zero_call_used_regs {
> > > +  zero_call_used_regs_unset = 0,
> > > +  zero_call_used_regs_skip,
> > > +  zero_call_used_regs_used_gpr,
> > > +  zero_call_used_regs_all_gpr,
> > > +  zero_call_used_regs_used,
> > > +  zero_call_used_regs_all
> > > +};
> > > +
> > > /* enums used by the targetm.excess_precision hook.  */
> > > 
> > > enum flt_eval_method
> > > diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
> > > index c800b74..b32c55f 100644
> > > --- a/gcc/doc/extend.texi
> > > +++ b/gcc/doc/extend.texi
> > > @@ -3984,6 +3984,17 @@ performing a link with relocatable output (i.e.@: @code{ld -r}) on them.
> > > A declaration to which @code{weakref} is attached and that is associated
> > > with a named @code{target} must be @code{static}.
> > > 
> > > +@item zero_call_used_regs ("@var{choice}")
> > > +@cindex @code{zero_call_used_regs} function attribute
> > > +The @code{zero_call_used_regs} attribute causes the compiler to zero
> > > +call-used registers at function return according to @var{choice}.
> > > +@samp{skip} doesn't zero call-used registers. @samp{used-gpr} zeros
> > > +call-used general purpose registers which are used in funciton.
> > > +@samp{all-gpr} zeros all call-used general purpose registers.
> > > +@samp{used} zeros call-used registers which are used in function.
> > > +@samp{all} zeros all call-used registers.  The default for the
> > > +attribute is controlled by @option{-fzero-call-used-regs}.
> > > +
> > > @end table
> > > 
> > > @c This is the end of the target-independent attribute table
> > > diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> > > index 09bcc5b..da02686 100644
> > > --- a/gcc/doc/invoke.texi
> > > +++ b/gcc/doc/invoke.texi
> > > @@ -542,7 +542,7 @@ Objective-C and Objective-C++ Dialects}.
> > > -funit-at-a-time  -funroll-all-loops  -funroll-loops @gol
> > > -funsafe-math-optimizations  -funswitch-loops @gol
> > > -fipa-ra  -fvariable-expansion-in-unroller  -fvect-cost-model  -fvpt @gol
> > > --fweb  -fwhole-program  -fwpa  -fuse-linker-plugin @gol
> > > +-fweb  -fwhole-program  -fwpa  -fuse-linker-plugin -fzero-call-used-regs @gol
> > > --param @var{name}=@var{value}
> > > -O  -O0  -O1  -O2  -O3  -Os  -Ofast  -Og}
> > > 
> > > @@ -12273,6 +12273,17 @@ int foo (void)
> > > 
> > > Not all targets support this option.
> > > 
> > > +@item -fzero-call-used-regs=@var{choice}
> > > +@opindex fzero-call-used-regs
> > > +Zero call-used registers at function return according to
> > > +@var{choice}.  @samp{skip}, which is the default, doesn't zero
> > > +call-used registers.  @samp{used-gpr} zeros call-used general purpose
> > > +registers which are used in function.  @samp{all-gpr} zeros all
> > > +call-used registers.  @samp{used} zeros call-used registers which
> > > +are used in function.  @samp{all} zeros all call-used registers.  You
> > > +can control this behavior for a specific function by using the function
> > > +attribute @code{zero_call_used_regs}.  @xref{Function Attributes}.
> > > +
> > > @item --param @var{name}=@var{value}
> > > @opindex param
> > > In some places, GCC uses various constants to control the amount of
> > > diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
> > > index 6e7d9dc..43dddd3 100644
> > > --- a/gcc/doc/tm.texi
> > > +++ b/gcc/doc/tm.texi
> > > @@ -4571,6 +4571,22 @@ should recognize only the caller's register numbers.
> > > If this hook is not defined, then FUNCTION_VALUE_REGNO_P will be used.
> > > @end deftypefn
> > > 
> > > +@deftypefn {Target Hook} bool TARGET_ZERO_CALL_USED_REGNO_P (const unsigned int @var{regno}, bool @var{general_reg_only_p})
> > > +A target hook that returns @code{true} if @var{regno} is the number of a
> > > +call used register.  If @var{general_reg_only_p} is @code{true},
> > > +@var{regno} must be the number of a hard general register.
> > > +
> > > +If this hook is not defined, then default_zero_call_used_regno_p will be used.
> > > +@end deftypefn
> > > +
> > > +@deftypefn {Target Hook} machine_mode TARGET_ZERO_CALL_USED_REGNO_MODE (const unsigned int @var{regno}, machine_mode @var{mode})
> > > +A target hook that returns a mode of suitable to zero the register for the
> > > +call used register @var{regno} in @var{mode}.
> > > +
> > > +If this hook is not defined, then default_zero_call_used_regno_mode will be
> > > +used.
> > > +@end deftypefn
> > > +
> > > @defmac APPLY_RESULT_SIZE
> > > Define this macro if @samp{untyped_call} and @samp{untyped_return}
> > > need more space than is implied by @code{FUNCTION_VALUE_REGNO_P} for
> > > @@ -12043,6 +12059,17 @@ argument list due to stack realignment.  Return @code{NULL} if no DRAP
> > > is needed.
> > > @end deftypefn
> > > 
> > > +@deftypefn {Target Hook} rtx TARGET_PRO_EPILOGUE_USE (rtx @var{reg})
> > > +This hook should return a UNSPEC_VOLATILE rtx to mark a register in use to
> > > +prevent deleting register setting instructions in proprologue and epilogue.
> > > +@end deftypefn
> > > +
> > > +@deftypefn {Target Hook} rtx TARGET_ZERO_ALL_VECTOR_REGISTERS (bool @var{used_only})
> > > +This hook should return an rtx to zero all vector registers at function
> > > +exit.  If @var{used_only} is @code{true}, only used vector registers should
> > > +be zeroed.  Return @code{NULL} if possible
> > > +@end deftypefn
> > > +
> > > @deftypefn {Target Hook} bool TARGET_ALLOCATE_STACK_SLOTS_FOR_ARGS (void)
> > > When optimization is disabled, this hook indicates whether or not
> > > arguments should be allocated to stack slots.  Normally, GCC allocates
> > > diff --git a/gcc/doc/tm.texi.in <http://tm.texi.in/> b/gcc/doc/tm.texi.in <http://tm.texi.in/>
> > > index 3be984b..bee917a 100644
> > > --- a/gcc/doc/tm.texi.in <http://tm.texi.in/>
> > > +++ b/gcc/doc/tm.texi.in <http://tm.texi.in/>
> > > @@ -3430,6 +3430,10 @@ for a new target instead.
> > > 
> > > @hook TARGET_FUNCTION_VALUE_REGNO_P
> > > 
> > > +@hook TARGET_ZERO_CALL_USED_REGNO_P
> > > +
> > > +@hook TARGET_ZERO_CALL_USED_REGNO_MODE
> > > +
> > > @defmac APPLY_RESULT_SIZE
> > > Define this macro if @samp{untyped_call} and @samp{untyped_return}
> > > need more space than is implied by @code{FUNCTION_VALUE_REGNO_P} for
> > > @@ -8109,6 +8113,10 @@ and the associated definitions of those functions.
> > > 
> > > @hook TARGET_GET_DRAP_RTX
> > > 
> > > +@hook TARGET_PRO_EPILOGUE_USE
> > > +
> > > +@hook TARGET_ZERO_ALL_VECTOR_REGISTERS
> > > +
> > > @hook TARGET_ALLOCATE_STACK_SLOTS_FOR_ARGS
> > > 
> > > @hook TARGET_CONST_ANCHOR
> > > diff --git a/gcc/function.c b/gcc/function.c
> > > index 9eee9b5..9908530 100644
> > > --- a/gcc/function.c
> > > +++ b/gcc/function.c
> > > @@ -50,6 +50,7 @@ along with GCC; see the file COPYING3.  If not see
> > > #include "emit-rtl.h"
> > > #include "recog.h"
> > > #include "rtl-error.h"
> > > +#include "hard-reg-set.h"
> > > #include "alias.h"
> > > #include "fold-const.h"
> > > #include "stor-layout.h"
> > > @@ -5808,6 +5809,147 @@ make_prologue_seq (void)
> > >  return seq;
> > > }
> > > 
> > > +/* Check whether the hard register REGNO is live at the exit block
> > > + * of the current routine.  */
> > > +bool
> > > +is_live_reg_at_exit (unsigned int regno)
> > > +{
> > > +  edge e;
> > > +  edge_iterator ei;
> > > +
> > > +  FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR_FOR_FN (cfun)->preds)
> > > +    {
> > > +      bitmap live_out = df_get_live_out (e->src);
> > > +      if (REGNO_REG_SET_P (live_out, regno))
> > > +     return true;
> > > +    }
> > > +
> > > +  return false;
> > > +}
> > > +
> > > +/* Emit a sequence of insns to zero the call-used-registers for the current
> > > + * function.  */
> > > +
> > > +static void
> > > +gen_call_used_regs_seq (void)
> > > +{
> > > +  if (!targetm.calls.pro_epilogue_use)
> > > +    return;
> > > +
> > > +  bool gpr_only = true;
> > > +  bool used_only = true;
> > > +  enum zero_call_used_regs zero_call_used_regs_type = zero_call_used_regs_unset;
> > > +
> > > +  if (flag_zero_call_used_regs)
> > > +    if (DECL_ZERO_CALL_USED_REGS (current_function_decl)
> > > +     == zero_call_used_regs_unset)
> > > +      zero_call_used_regs_type = flag_zero_call_used_regs;
> > > +    else
> > > +      zero_call_used_regs_type
> > > +     = DECL_ZERO_CALL_USED_REGS (current_function_decl);
> > > +  else
> > > +    zero_call_used_regs_type = DECL_ZERO_CALL_USED_REGS (current_function_decl);
> > > +
> > > +  /* No need to zero call-used-regs when no user request is present.  */
> > > +  if (zero_call_used_regs_type <= zero_call_used_regs_skip)
> > > +    return;
> > > +
> > > +  /* No need to zero call-used-regs in main ().  */
> > > +  if (MAIN_NAME_P (DECL_NAME (current_function_decl)))
> > > +    return;
> > > +
> > > +  /* No need to zero call-used-regs if __builtin_eh_return is called
> > > +     since it isn't a normal function return.  */
> > > +  if (crtl->calls_eh_return)
> > > +    return;
> > > +
> > > +  /* If gpr_only is true, only zero call-used-registers that are
> > > +     general-purpose registers; if used_only is true, only zero
> > > +     call-used-registers that are used in the current function.  */
> > > +  switch (zero_call_used_regs_type)
> > > +    {
> > > +      case zero_call_used_regs_all_gpr:
> > > +     used_only = false;
> > > +     break;
> > > +      case zero_call_used_regs_used:
> > > +     gpr_only = false;
> > > +     break;
> > > +      case zero_call_used_regs_all:
> > > +     gpr_only = false;
> > > +     used_only = false;
> > > +     break;
> > > +      default:
> > > +     break;
> > > +    }
> > > +
> > > +  /* An optimization to use a single hard insn to zero all vector registers on
> > > +     the target that provides such insn.  */
> > > +  if (!gpr_only
> > > +      && targetm.calls.zero_all_vector_registers)
> > > +    {
> > > +      rtx zero_all_vec_insn
> > > +     = targetm.calls.zero_all_vector_registers (used_only);
> > > +      if (zero_all_vec_insn)
> > > +     {
> > > +       emit_insn (zero_all_vec_insn);
> > > +       gpr_only = true;
> > > +     }
> > > +    }
> > > +
> > > +  /* For each of the hard registers, check to see whether we should zero it if:
> > > +     1. it is a call-used-registers;
> > > + and 2. it is not a fixed-registers;
> > > + and 3. it is not live at the end of the routine;
> > > + and 4. it is general purpose register if gpr_only is true;
> > > + and 5. it is used in the routine if used_only is true;
> > > +   */
> > > +
> > > +  /* This array holds the zero rtx with the correponding machine mode.  */
> > > +  rtx zero_rtx[(int)MAX_MACHINE_MODE];
> > > +  for (int i = 0; i < (int) MAX_MACHINE_MODE; i++)
> > > +    zero_rtx[i] = NULL_RTX;
> > > +
> > > +  for (unsigned int regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
> > > +    {
> > > +      if (!this_target_hard_regs->x_call_used_regs[regno])
> > > +     continue;
> > > +      if (fixed_regs[regno])
> > > +     continue;
> > > +      if (is_live_reg_at_exit (regno))
> > > +     continue;
> > > +      if (!targetm.calls.zero_call_used_regno_p (regno, gpr_only))
> > > +     continue;
> > > +      if (used_only && !df_regs_ever_live_p (regno))
> > > +     continue;
> > > +
> > > +      /* Now we can emit insn to zero this register.  */
> > > +      rtx reg, tmp;
> > > +
> > > +      machine_mode mode
> > > +     = targetm.calls.zero_call_used_regno_mode (regno,
> > > +                                                reg_raw_mode[regno]);
> > > +      if (mode == VOIDmode)
> > > +     continue;
> > > +      if (!have_regs_of_mode[mode])
> > > +     continue;
> > > +
> > > +      reg = gen_rtx_REG (mode, regno);
> > > +      if (zero_rtx[(int)mode] == NULL_RTX)
> > > +     {
> > > +       zero_rtx[(int)mode] = reg;
> > > +       tmp = gen_rtx_SET (reg, const0_rtx);
> > > +       emit_insn (tmp);
> > > +     }
> > > +      else
> > > +     emit_move_insn (reg, zero_rtx[(int)mode]);
> > > +
> > > +      emit_insn (targetm.calls.pro_epilogue_use (reg));
> > > +    }
> > > +
> > > +  return;
> > > +}
> > > +
> > > +
> > > /* Return a sequence to be used as the epilogue for the current function,
> > >   or NULL.  */
> > > 
> > > @@ -5819,6 +5961,9 @@ make_epilogue_seq (void)
> > > 
> > >  start_sequence ();
> > >  emit_note (NOTE_INSN_EPILOGUE_BEG);
> > > +
> > > +  gen_call_used_regs_seq ();
> > > +
> > >  rtx_insn *seq = targetm.gen_epilogue ();
> > >  if (seq)
> > >    emit_jump_insn (seq);
> > > diff --git a/gcc/function.h b/gcc/function.h
> > > index d55cbdd..fc36c3e 100644
> > > --- a/gcc/function.h
> > > +++ b/gcc/function.h
> > > @@ -705,4 +705,6 @@ extern const char *current_function_name (void);
> > > 
> > > extern void used_types_insert (tree);
> > > 
> > > +extern bool is_live_reg_at_exit (unsigned int);
> > > +
> > > #endif  /* GCC_FUNCTION_H */
> > > diff --git a/gcc/target.def b/gcc/target.def
> > > index 07059a8..8aab63e 100644
> > > --- a/gcc/target.def
> > > +++ b/gcc/target.def
> > > @@ -5022,6 +5022,26 @@ If this hook is not defined, then FUNCTION_VALUE_REGNO_P will be used.",
> > > default_function_value_regno_p)
> > > 
> > > DEFHOOK
> > > +(zero_call_used_regno_p,
> > > + "A target hook that returns @code{true} if @var{regno} is the number of a\n\
> > > +call used register.  If @var{general_reg_only_p} is @code{true},\n\
> > > +@var{regno} must be the number of a hard general register.\n\
> > > +\n\
> > > +If this hook is not defined, then default_zero_call_used_regno_p will be used.",
> > > + bool, (const unsigned int regno, bool general_reg_only_p),
> > > + default_zero_call_used_regno_p)
> > > +
> > > +DEFHOOK
> > > +(zero_call_used_regno_mode,
> > > + "A target hook that returns a mode of suitable to zero the register for the\n\
> > > +call used register @var{regno} in @var{mode}.\n\
> > > +\n\
> > > +If this hook is not defined, then default_zero_call_used_regno_mode will be\n\
> > > +used.",
> > > + machine_mode, (const unsigned int regno, machine_mode mode),
> > > + default_zero_call_used_regno_mode)
> > > +
> > > +DEFHOOK
> > > (fntype_abi,
> > > "Return the ABI used by a function with type @var{type}; see the\n\
> > > definition of @code{predefined_function_abi} for details of the ABI\n\
> > > @@ -5068,6 +5088,19 @@ argument list due to stack realignment.  Return @code{NULL} if no DRAP\n\
> > > is needed.",
> > > rtx, (void), NULL)
> > > 
> > > +DEFHOOK
> > > +(pro_epilogue_use,
> > > + "This hook should return a UNSPEC_VOLATILE rtx to mark a register in use to\n\
> > > +prevent deleting register setting instructions in proprologue and epilogue.",
> > > + rtx, (rtx reg), NULL)
> > > +
> > > +DEFHOOK
> > > +(zero_all_vector_registers,
> > > + "This hook should return an rtx to zero all vector registers at function\n\
> > > +exit.  If @var{used_only} is @code{true}, only used vector registers should\n\
> > > +be zeroed.  Return @code{NULL} if possible",
> > > + rtx, (bool used_only), NULL)
> > > +
> > > /* Return true if all function parameters should be spilled to the
> > >   stack.  */
> > > DEFHOOK
> > > diff --git a/gcc/targhooks.c b/gcc/targhooks.c
> > > index 0113c7b..ed02173 100644
> > > --- a/gcc/targhooks.c
> > > +++ b/gcc/targhooks.c
> > > @@ -987,6 +987,23 @@ default_function_value_regno_p (const unsigned int regno ATTRIBUTE_UNUSED)
> > > #endif
> > > }
> > > 
> > > +/* The default hook for TARGET_ZERO_CALL_USED_REGNO_P.  */
> > > +
> > > +bool
> > > +default_zero_call_used_regno_p (const unsigned int,
> > > +                             bool)
> > > +{
> > > +  return false;
> > > +}
> > > +
> > > +/* The default hook for TARGET_ZERO_CALL_USED_REGNO_MODE.  */
> > > +
> > > +machine_mode
> > > +default_zero_call_used_regno_mode (const unsigned int, machine_mode mode)
> > > +{
> > > +  return mode;
> > > +}
> > > +
> > > rtx
> > > default_internal_arg_pointer (void)
> > > {
> > > diff --git a/gcc/targhooks.h b/gcc/targhooks.h
> > > index b572a36..370df19 100644
> > > --- a/gcc/targhooks.h
> > > +++ b/gcc/targhooks.h
> > > @@ -162,6 +162,9 @@ extern bool hook_bool_const_rtx_commutative_p (const_rtx, int);
> > > extern rtx default_function_value (const_tree, const_tree, bool);
> > > extern rtx default_libcall_value (machine_mode, const_rtx);
> > > extern bool default_function_value_regno_p (const unsigned int);
> > > +extern bool default_zero_call_used_regno_p (const unsigned int, bool);
> > > +extern machine_mode default_zero_call_used_regno_mode (const unsigned int,
> > > +                                                    machine_mode);
> > > extern rtx default_internal_arg_pointer (void);
> > > extern rtx default_static_chain (const_tree, bool);
> > > extern void default_trampoline_init (rtx, tree, rtx);
> > > diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-1.c b/gcc/testsuite/c-c++-common/zero-scratch-regs-1.c
> > > new file mode 100644
> > > index 0000000..3c2ac72
> > > --- /dev/null
> > > +++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-1.c
> > > @@ -0,0 +1,3 @@
> > > +/* { dg-do compile } */
> > > +/* { dg-options "-O2 -fzero-call-used-regs=used" } */
> > > +/* { dg-error "'-fzero-call-used-regs=' is not supported for this target" "" { target { ! "i?86-*-* x86_64-*-*" } } 0 } */
> > > diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-2.c b/gcc/testsuite/c-c++-common/zero-scratch-regs-2.c
> > > new file mode 100644
> > > index 0000000..acf48c4
> > > --- /dev/null
> > > +++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-2.c
> > > @@ -0,0 +1,4 @@
> > > +/* { dg-do compile { target *-*-linux* } } */
> > > +/* { dg-options "-O2" } */
> > > +
> > > +extern int foo (int) __attribute__ ((zero_call_used_regs("all-gpr"))); /* { dg-warning " attribute directive ignored" "" {target { ! "i?86-*-* x86_64-*-*" } } 0 } */
> > > diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-1.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-1.c
> > > new file mode 100644
> > > index 0000000..9f61dc4
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-1.c
> > > @@ -0,0 +1,12 @@
> > > +/* { dg-do compile { target *-*-linux* } } */
> > > +/* { dg-options "-O2 -fzero-call-used-regs=used" } */
> > > +
> > > +void
> > > +foo (void)
> > > +{
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "vzeroall" } } */
> > > +/* { dg-final { scan-assembler-not "%xmm" } } */
> > > +/* { dg-final { scan-assembler-not "xorl\[ \t\]*%" } } */
> > > +/* { dg-final { scan-assembler-not "movl\[ \t\]*%" } } */
> > > diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-10.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-10.c
> > > new file mode 100644
> > > index 0000000..09048e5
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-10.c
> > > @@ -0,0 +1,21 @@
> > > +/* { dg-do compile { target *-*-linux* } } */
> > > +/* { dg-options "-O2 -fzero-call-used-regs=skip" } */
> > > +
> > > +extern int foo (int) __attribute__ ((zero_call_used_regs("all-gpr")));
> > > +
> > > +int
> > > +foo (int x)
> > > +{
> > > +  return x;
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "vzeroall" } } */
> > > +/* { dg-final { scan-assembler-not "%xmm" } } */
> > > +/* { dg-final { scan-assembler "xorl\[ \t\]*%edx, %edx" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %ecx" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %esi" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %edi" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %r8d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %r9d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %r10d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %r11d" { target { ! ia32 } } } } */
> > > diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-11.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-11.c
> > > new file mode 100644
> > > index 0000000..4862688
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-11.c
> > > @@ -0,0 +1,39 @@
> > > +/* { dg-do run { target *-*-linux* } } */
> > > +/* { dg-options "-O2 -fzero-call-used-regs=used-gpr" } */
> > > +
> > > +struct S { int i; };
> > > +__attribute__((const, noinline, noclone))
> > > +struct S foo (int x)
> > > +{
> > > +  struct S s;
> > > +  s.i = x;
> > > +  return s;
> > > +}
> > > +
> > > +int a[2048], b[2048], c[2048], d[2048];
> > > +struct S e[2048];
> > > +
> > > +__attribute__((noinline, noclone)) void
> > > +bar (void)
> > > +{
> > > +  int i;
> > > +  for (i = 0; i < 1024; i++)
> > > +    {
> > > +      e[i] = foo (i);
> > > +      a[i+2] = a[i] + a[i+1];
> > > +      b[10] = b[10] + i;
> > > +      c[i] = c[2047 - i];
> > > +      d[i] = d[i + 1];
> > > +    }
> > > +}
> > > +
> > > +int
> > > +main ()
> > > +{
> > > +  int i;
> > > +  bar ();
> > > +  for (i = 0; i < 1024; i++)
> > > +    if (e[i].i != i)
> > > +      __builtin_abort ();
> > > +  return 0;
> > > +}
> > > diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-12.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-12.c
> > > new file mode 100644
> > > index 0000000..500251b
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-12.c
> > > @@ -0,0 +1,39 @@
> > > +/* { dg-do run { target *-*-linux* } } */
> > > +/* { dg-options "-O2 -fzero-call-used-regs=all-gpr" } */
> > > +
> > > +struct S { int i; };
> > > +__attribute__((const, noinline, noclone))
> > > +struct S foo (int x)
> > > +{
> > > +  struct S s;
> > > +  s.i = x;
> > > +  return s;
> > > +}
> > > +
> > > +int a[2048], b[2048], c[2048], d[2048];
> > > +struct S e[2048];
> > > +
> > > +__attribute__((noinline, noclone)) void
> > > +bar (void)
> > > +{
> > > +  int i;
> > > +  for (i = 0; i < 1024; i++)
> > > +    {
> > > +      e[i] = foo (i);
> > > +      a[i+2] = a[i] + a[i+1];
> > > +      b[10] = b[10] + i;
> > > +      c[i] = c[2047 - i];
> > > +      d[i] = d[i + 1];
> > > +    }
> > > +}
> > > +
> > > +int
> > > +main ()
> > > +{
> > > +  int i;
> > > +  bar ();
> > > +  for (i = 0; i < 1024; i++)
> > > +    if (e[i].i != i)
> > > +      __builtin_abort ();
> > > +  return 0;
> > > +}
> > > diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-13.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-13.c
> > > new file mode 100644
> > > index 0000000..8b058e3
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-13.c
> > > @@ -0,0 +1,21 @@
> > > +/* { dg-do compile { target *-*-linux* } } */
> > > +/* { dg-options "-O2 -fzero-call-used-regs=all -march=corei7" } */
> > > +
> > > +void
> > > +foo (void)
> > > +{
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "vzeroall" } } */
> > > +/* { dg-final { scan-assembler "pxor\[ \t\]*%xmm0, %xmm0" } } */
> > > +/* { dg-final { scan-assembler-times "movaps\[ \t\]*%xmm0, %xmm\[0-9\]+" 7 { target { ia32 } } } } */
> > > +/* { dg-final { scan-assembler-times "movaps\[ \t\]*%xmm0, %xmm\[0-9\]+" 15 { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "xorl\[ \t\]*%eax, %eax" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edx" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %ecx" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %esi" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edi" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r8d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r9d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r10d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r11d" { target { ! ia32 } } } } */
> > > diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-14.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-14.c
> > > new file mode 100644
> > > index 0000000..d4eaaf7
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-14.c
> > > @@ -0,0 +1,19 @@
> > > +/* { dg-do compile { target *-*-linux* } } */
> > > +/* { dg-options "-O2 -fzero-call-used-regs=all -march=corei7 -mavx" } */
> > > +
> > > +void
> > > +foo (void)
> > > +{
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-times "vzeroall" 1 } } */
> > > +/* { dg-final { scan-assembler-not "%xmm" } } */
> > > +/* { dg-final { scan-assembler "xorl\[ \t\]*%eax, %eax" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edx" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %ecx" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %esi" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edi" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r8d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r9d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r10d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r11d" { target { ! ia32 } } } } */
> > > diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-15.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-15.c
> > > new file mode 100644
> > > index 0000000..dd3bb90
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-15.c
> > > @@ -0,0 +1,14 @@
> > > +/* { dg-do compile { target *-*-linux* } } */
> > > +/* { dg-options "-O2 -fzero-call-used-regs=skip" } */
> > > +
> > > +extern void foo (void) __attribute__ ((zero_call_used_regs("used")));
> > > +
> > > +void
> > > +foo (void)
> > > +{
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "vzeroall" } } */
> > > +/* { dg-final { scan-assembler-not "%xmm" } } */
> > > +/* { dg-final { scan-assembler-not "xorl\[ \t\]*%" } } */
> > > +/* { dg-final { scan-assembler-not "movl\[ \t\]*%" } } */
> > > diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-16.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-16.c
> > > new file mode 100644
> > > index 0000000..e2274f6
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-16.c
> > > @@ -0,0 +1,14 @@
> > > +/* { dg-do compile { target *-*-linux* } } */
> > > +/* { dg-options "-O2 -fzero-call-used-regs=all" } */
> > > +
> > > +extern void foo (void) __attribute__ ((zero_call_used_regs("skip")));
> > > +
> > > +void
> > > +foo (void)
> > > +{
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "vzeroall" } } */
> > > +/* { dg-final { scan-assembler-not "%xmm" } } */
> > > +/* { dg-final { scan-assembler-not "xorl\[ \t\]*%" } } */
> > > +/* { dg-final { scan-assembler-not "movl\[ \t\]*%" } } */
> > > diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-17.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-17.c
> > > new file mode 100644
> > > index 0000000..7f5d153
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-17.c
> > > @@ -0,0 +1,13 @@
> > > +/* { dg-do compile { target *-*-linux* } } */
> > > +/* { dg-options "-O2 -fzero-call-used-regs=used" } */
> > > +
> > > +int
> > > +foo (int x)
> > > +{
> > > +  return x;
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "vzeroall" } } */
> > > +/* { dg-final { scan-assembler-not "%xmm" } } */
> > > +/* { dg-final { scan-assembler-not "xorl\[ \t\]*%" { target ia32 } } } */
> > > +/* { dg-final { scan-assembler "xorl\[ \t\]*%edi, %edi" { target { ! ia32 } } } } */
> > > diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-18.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-18.c
> > > new file mode 100644
> > > index 0000000..fe13d2b
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-18.c
> > > @@ -0,0 +1,13 @@
> > > +/* { dg-do compile { target *-*-linux* } } */
> > > +/* { dg-options "-O2 -fzero-call-used-regs=used -march=corei7" } */
> > > +
> > > +float
> > > +foo (float z, float y, float x)
> > > +{
> > > +  return x + y;
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "vzeroall" } } */
> > > +/* { dg-final { scan-assembler "pxor\[ \t\]*%xmm1, %xmm1" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movaps\[ \t\]*%xmm1, %xmm2" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler-not "xorl\[ \t\]*%" } } */
> > > diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-19.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-19.c
> > > new file mode 100644
> > > index 0000000..205a532
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-19.c
> > > @@ -0,0 +1,12 @@
> > > +/* { dg-do compile { target *-*-linux* } } */
> > > +/* { dg-options "-O2 -fzero-call-used-regs=used -march=corei7" } */
> > > +
> > > +float
> > > +foo (float z, float y, float x)
> > > +{
> > > +  return x;
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "vzeroall" } } */
> > > +/* { dg-final { scan-assembler "pxor\[ \t\]*%xmm2, %xmm2" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler-not "xorl\[ \t\]*%" } } */
> > > diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-2.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-2.c
> > > new file mode 100644
> > > index 0000000..e046684
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-2.c
> > > @@ -0,0 +1,19 @@
> > > +/* { dg-do compile { target *-*-linux* } } */
> > > +/* { dg-options "-O2 -fzero-call-used-regs=all-gpr" } */
> > > +
> > > +void
> > > +foo (void)
> > > +{
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "vzeroall" } } */
> > > +/* { dg-final { scan-assembler-not "%xmm" } } */
> > > +/* { dg-final { scan-assembler "xorl\[ \t\]*%eax, %eax" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edx" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %ecx" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %esi" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edi" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r8d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r9d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r10d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r11d" { target { ! ia32 } } } } */
> > > diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-20.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-20.c
> > > new file mode 100644
> > > index 0000000..4be8ff6
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-20.c
> > > @@ -0,0 +1,23 @@
> > > +/* { dg-do compile { target *-*-linux* } } */
> > > +/* { dg-options "-O2 -fzero-call-used-regs=all -march=corei7" } */
> > > +
> > > +float
> > > +foo (float z, float y, float x)
> > > +{
> > > +  return x + y;
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "vzeroall" } } */
> > > +/* { dg-final { scan-assembler "pxor\[ \t\]*%xmm0, %xmm0" { target { ia32 } } } } */
> > > +/* { dg-final { scan-assembler "pxor\[ \t\]*%xmm1, %xmm1" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler-times "movaps\[ \t\]*%xmm0, %xmm\[0-9\]+" 7 { target { ia32 } } } } */
> > > +/* { dg-final { scan-assembler-times "movaps\[ \t\]*%xmm1, %xmm\[0-9\]+" 14 { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "xorl\[ \t\]*%eax, %eax" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edx" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %ecx" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %esi" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edi" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r8d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r9d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r10d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r11d" { target { ! ia32 } } } } */
> > > diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-21.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-21.c
> > > new file mode 100644
> > > index 0000000..0eb34e0
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-21.c
> > > @@ -0,0 +1,14 @@
> > > +/* { dg-do compile { target *-*-linux* } } */
> > > +/* { dg-options "-O2 -fzero-call-used-regs=skip -march=corei7" } */
> > > +
> > > +__attribute__ ((zero_call_used_regs("used")))
> > > +float
> > > +foo (float z, float y, float x)
> > > +{
> > > +  return x + y;
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "vzeroall" } } */
> > > +/* { dg-final { scan-assembler "pxor\[ \t\]*%xmm1, %xmm1" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movaps\[ \t\]*%xmm1, %xmm2" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler-not "xorl\[ \t\]*%" } } */
> > > diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-22.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-22.c
> > > new file mode 100644
> > > index 0000000..cbb63a4
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-22.c
> > > @@ -0,0 +1,19 @@
> > > +/* { dg-do compile { target *-*-linux* } } */
> > > +/* { dg-options "-O2 -fzero-call-used-regs=all -march=corei7 -mavx" } */
> > > +
> > > +void
> > > +foo (void)
> > > +{
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler "vzeroall" } } */
> > > +/* { dg-final { scan-assembler-not "%xmm" } } */
> > > +/* { dg-final { scan-assembler "xorl\[ \t\]*%eax, %eax" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edx" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %ecx" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %esi" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edi" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r8d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r9d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r10d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r11d" { target { ! ia32 } } } } */
> > > diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-23.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-23.c
> > > new file mode 100644
> > > index 0000000..7573197
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-23.c
> > > @@ -0,0 +1,19 @@
> > > +/* { dg-do compile { target *-*-linux* } } */
> > > +/* { dg-options "-O2 -fzero-call-used-regs=all -march=corei7 -mavx512f" } */
> > > +
> > > +void
> > > +foo (void)
> > > +{
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler "vzeroall" } } */
> > > +/* { dg-final { scan-assembler-not "%xmm" } } */
> > > +/* { dg-final { scan-assembler "xorl\[ \t\]*%eax, %eax" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edx" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %ecx" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %esi" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edi" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r8d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r9d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r10d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r11d" { target { ! ia32 } } } } */
> > > diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-3.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-3.c
> > > new file mode 100644
> > > index 0000000..de71223
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-3.c
> > > @@ -0,0 +1,12 @@
> > > +/* { dg-do compile { target *-*-linux* } } */
> > > +/* { dg-options "-O2 -fzero-call-used-regs=skip" } */
> > > +
> > > +void
> > > +foo (void)
> > > +{
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "vzeroall" } } */
> > > +/* { dg-final { scan-assembler-not "%xmm" } } */
> > > +/* { dg-final { scan-assembler-not "xorl\[ \t\]*%" } } */
> > > +/* { dg-final { scan-assembler-not "movl\[ \t\]*%" } } */
> > > diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-4.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-4.c
> > > new file mode 100644
> > > index 0000000..ccfa441
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-4.c
> > > @@ -0,0 +1,14 @@
> > > +/* { dg-do compile { target *-*-linux* } } */
> > > +/* { dg-options "-O2 -fzero-call-used-regs=skip" } */
> > > +
> > > +extern void foo (void) __attribute__ ((zero_call_used_regs("used-gpr")));
> > > +
> > > +void
> > > +foo (void)
> > > +{
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "vzeroall" } } */
> > > +/* { dg-final { scan-assembler-not "%xmm" } } */
> > > +/* { dg-final { scan-assembler-not "xorl\[ \t\]*%" } } */
> > > +/* { dg-final { scan-assembler-not "movl\[ \t\]*%" } } */
> > > diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-5.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-5.c
> > > new file mode 100644
> > > index 0000000..6b46ca3
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-5.c
> > > @@ -0,0 +1,20 @@
> > > +/* { dg-do compile { target *-*-linux* } } */
> > > +/* { dg-options "-O2 -fzero-call-used-regs=skip" } */
> > > +
> > > +__attribute__ ((zero_call_used_regs("all-gpr")))
> > > +void
> > > +foo (void)
> > > +{
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "vzeroall" } } */
> > > +/* { dg-final { scan-assembler-not "%xmm" } } */
> > > +/* { dg-final { scan-assembler "xorl\[ \t\]*%eax, %eax" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edx" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %ecx" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %esi" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edi" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r8d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r9d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r10d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r11d" { target { ! ia32 } } } } */
> > > diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-6.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-6.c
> > > new file mode 100644
> > > index 0000000..0680f38
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-6.c
> > > @@ -0,0 +1,14 @@
> > > +/* { dg-do compile { target *-*-linux* } } */
> > > +/* { dg-options "-O2 -fzero-call-used-regs=all-gpr" } */
> > > +
> > > +extern void foo (void) __attribute__ ((zero_call_used_regs("skip")));
> > > +
> > > +void
> > > +foo (void)
> > > +{
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "vzeroall" } } */
> > > +/* { dg-final { scan-assembler-not "%xmm" } } */
> > > +/* { dg-final { scan-assembler-not "xorl\[ \t\]*%" } } */
> > > +/* { dg-final { scan-assembler-not "movl\[ \t\]*%" } } */
> > > diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-7.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-7.c
> > > new file mode 100644
> > > index 0000000..534defa
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-7.c
> > > @@ -0,0 +1,13 @@
> > > +/* { dg-do compile { target *-*-linux* } } */
> > > +/* { dg-options "-O2 -fzero-call-used-regs=used-gpr" } */
> > > +
> > > +int
> > > +foo (int x)
> > > +{
> > > +  return x;
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "vzeroall" } } */
> > > +/* { dg-final { scan-assembler-not "%xmm" } } */
> > > +/* { dg-final { scan-assembler-not "xorl\[ \t\]*%" { target ia32 } } } */
> > > +/* { dg-final { scan-assembler "xorl\[ \t\]*%edi, %edi" { target { ! ia32 } } } } */
> > > diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-8.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-8.c
> > > new file mode 100644
> > > index 0000000..477bb19
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-8.c
> > > @@ -0,0 +1,19 @@
> > > +/* { dg-do compile { target *-*-linux* } } */
> > > +/* { dg-options "-O2 -fzero-call-used-regs=all-gpr" } */
> > > +
> > > +int
> > > +foo (int x)
> > > +{
> > > +  return x;
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "vzeroall" } } */
> > > +/* { dg-final { scan-assembler-not "%xmm" } } */
> > > +/* { dg-final { scan-assembler "xorl\[ \t\]*%edx, %edx" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %ecx" } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %esi" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %edi" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %r8d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %r9d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %r10d" { target { ! ia32 } } } } */
> > > +/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %r11d" { target { ! ia32 } } } } */
> > > diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-9.c b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-9.c
> > > new file mode 100644
> > > index 0000000..a305a60
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-9.c
> > > @@ -0,0 +1,15 @@
> > > +/* { dg-do compile { target *-*-linux* } } */
> > > +/* { dg-options "-O2 -fzero-call-used-regs=skip" } */
> > > +
> > > +extern int foo (int) __attribute__ ((zero_call_used_regs("used-gpr")));
> > > +
> > > +int
> > > +foo (int x)
> > > +{
> > > +  return x;
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "vzeroall" } } */
> > > +/* { dg-final { scan-assembler-not "%xmm" } } */
> > > +/* { dg-final { scan-assembler-not "xorl\[ \t\]*%" { target ia32 } } } */
> > > +/* { dg-final { scan-assembler "xorl\[ \t\]*%edi, %edi" { target { ! ia32 } } } } */
> > > diff --git a/gcc/toplev.c b/gcc/toplev.c
> > > index 95eea63..01a1f24 100644
> > > --- a/gcc/toplev.c
> > > +++ b/gcc/toplev.c
> > > @@ -1464,6 +1464,15 @@ process_options (void)
> > >       }
> > >    }
> > > 
> > > +  if (flag_zero_call_used_regs != zero_call_used_regs_skip
> > > +      && !targetm.calls.pro_epilogue_use)
> > > +    {
> > > +      error_at (UNKNOWN_LOCATION,
> > > +             "%<-fzero-call-used-regs=%> is not supported for this "
> > > +             "target");
> > > +      flag_zero_call_used_regs = zero_call_used_regs_skip;
> > > +    }
> > > +
> > >  /* One region RA really helps to decrease the code size.  */
> > >  if (flag_ira_region == IRA_REGION_AUTODETECT)
> > >    flag_ira_region
> > > diff --git a/gcc/tree-core.h b/gcc/tree-core.h
> > > index 8c5a2e3..71badbd 100644
> > > --- a/gcc/tree-core.h
> > > +++ b/gcc/tree-core.h
> > > @@ -1825,7 +1825,11 @@ struct GTY(()) tree_decl_with_vis {
> > > unsigned final : 1;
> > > /* Belong to FUNCTION_DECL exclusively.  */
> > > unsigned regdecl_flag : 1;
> > > - /* 14 unused bits. */
> > > +
> > > + /* How to clear call-used registers upon function return.  */
> > > + ENUM_BITFIELD(zero_call_used_regs) zero_call_used_regs_type : 3;
> > > +
> > > + /* 11 unused bits.  */
> > > };
> > > 
> > > struct GTY(()) tree_var_decl {
> > > diff --git a/gcc/tree.h b/gcc/tree.h
> > > index cf546ed..d378a88 100644
> > > --- a/gcc/tree.h
> > > +++ b/gcc/tree.h
> > > @@ -2925,6 +2925,11 @@ extern void decl_value_expr_insert (tree, tree);
> > > #define DECL_VISIBILITY(NODE) \
> > >  (DECL_WITH_VIS_CHECK (NODE)->decl_with_vis.visibility)
> > > 
> > > +/* Value of the function decl's type of zeroing the call used
> > > +   registers upon return from function.  */
> > > +#define DECL_ZERO_CALL_USED_REGS(NODE) \
> > > +  (DECL_WITH_VIS_CHECK (NODE)->decl_with_vis.zero_call_used_regs_type)
> > > +
> > > /* Nonzero means that the decl (or an enclosing scope) had its
> > >   visibility specified rather than being inferred.  */
> > > #define DECL_VISIBILITY_SPECIFIED(NODE) \
> > > -- 
> > > 1.9.1
> >
> 



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