[PATCH] x86: Update 'P' operand modifier for -fno-plt

[H.J. Lu]

On Thu, Mar 11, 2021 at 11:21 PM Uros Bizjak <ubizjak@gmail.com> wrote:
>
> On Thu, Mar 11, 2021 at 11:22 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> >
> > Update 'P' operand modifier for -fno-plt to support inline assembly
> > statements.  In 64-bit, we can always load function address with
> > @GOTPCREL.  In 32-bit, we load function address with @GOT only for
> > non-PIC since PIC register may not be available at call site.
> >
> > gcc/
> >
> >         PR target/99504
> >         * config/i386/i386.c (ix86_print_operand): Update 'P' handling
> >         for -fno-plt.
> >
> > gcc/testsuite/
> >
> >         PR target/99504
> >         * gcc.target/i386/pr99530-1.c: New test.
> >         * gcc.target/i386/pr99530-2.c: Likewise.
> >         * gcc.target/i386/pr99530-3.c: Likewise.
> >         * gcc.target/i386/pr99530-4.c: Likewise.
> >         * gcc.target/i386/pr99530-5.c: Likewise.
> >         * gcc.target/i386/pr99530-6.c: Likewise.
> > ---
> >  gcc/config/i386/i386.c                    | 33 +++++++++++++++++++++--
> >  gcc/testsuite/gcc.target/i386/pr99530-1.c | 11 ++++++++
> >  gcc/testsuite/gcc.target/i386/pr99530-2.c | 11 ++++++++
> >  gcc/testsuite/gcc.target/i386/pr99530-3.c | 11 ++++++++
> >  gcc/testsuite/gcc.target/i386/pr99530-4.c | 11 ++++++++
> >  gcc/testsuite/gcc.target/i386/pr99530-5.c | 11 ++++++++
> >  gcc/testsuite/gcc.target/i386/pr99530-6.c | 11 ++++++++
> >  7 files changed, 97 insertions(+), 2 deletions(-)
> >  create mode 100644 gcc/testsuite/gcc.target/i386/pr99530-1.c
> >  create mode 100644 gcc/testsuite/gcc.target/i386/pr99530-2.c
> >  create mode 100644 gcc/testsuite/gcc.target/i386/pr99530-3.c
> >  create mode 100644 gcc/testsuite/gcc.target/i386/pr99530-4.c
> >  create mode 100644 gcc/testsuite/gcc.target/i386/pr99530-5.c
> >  create mode 100644 gcc/testsuite/gcc.target/i386/pr99530-6.c
> >
> > diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> > index 2603333f87b..8733fcecf65 100644
> > --- a/gcc/config/i386/i386.c
> > +++ b/gcc/config/i386/i386.c
> > @@ -12701,7 +12701,8 @@ print_reg (rtx x, int code, FILE *file)
> >     y -- print "st(0)" instead of "st" as a register.
> >     d -- print duplicated register operand for AVX instruction.
> >     D -- print condition for SSE cmp instruction.
> > -   P -- if PIC, print an @PLT suffix.
> > +   P -- if PIC, print an @PLT suffix.  For -fno-plt, load function
> > +       address from GOT.
> >     p -- print raw symbol name.
> >     X -- don't print any sort of PIC '@' suffix for a symbol.
> >     & -- print some in-use local-dynamic symbol name.
> > @@ -13445,7 +13446,35 @@ ix86_print_operand (FILE *file, rtx x, int code)
> >           x = const0_rtx;
> >         }
> >
> > -      if (code != 'P' && code != 'p')
> > +      if (code == 'P')
> > +       {
> > +         if (current_output_insn == NULL_RTX
> > +             && (TARGET_64BIT || (!flag_pic && HAVE_AS_IX86_GOT32X))
> > +             && !TARGET_PECOFF
> > +             && !TARGET_MACHO
> > +             && ix86_cmodel != CM_LARGE
> > +             && ix86_cmodel != CM_LARGE_PIC
> > +             && GET_CODE (x) == SYMBOL_REF
> > +             && SYMBOL_REF_FUNCTION_P (x)
> > +             && (!flag_plt
> > +                 || (SYMBOL_REF_DECL (x)
> > +                     && lookup_attribute ("noplt",
> > +                                          DECL_ATTRIBUTES (SYMBOL_REF_DECL (x)))))
> > +             && !SYMBOL_REF_LOCAL_P (x))
> > +           {
> > +             /* For inline assembly statement, load function address
> > +                from GOT with 'P' operand modifier to avoid PLT.
> > +                NB: This works only with call or jmp.  */
> > +             const char *xasm;
> > +             if (TARGET_64BIT)
> > +               xasm = "{*%p0@GOTPCREL(%%rip)|[QWORD PTR %p0@GOTPCREL[rip]]}";
> > +             else
> > +               xasm = "{*%p0@GOT|[DWORD PTR %p0@GOT]}";
> > +             output_asm_insn (xasm, &x);
> > +             return;
>
> This should be handled in output_pic_addr_const.
>

call/jmp are special and are handled by ix86_output_call_insn,
not output_pic_addr_const.

H.J.