Re: [PATCH, rs6000] Fold vector shifts in GIMPLE

[Will Schmidt <will_schmidt at vnet dot ibm dot com>]

On Thu, 2017-06-01 at 10:15 -0500, Bill Schmidt wrote:
> > On Jun 1, 2017, at 2:48 AM, Richard Biener <richard.guenther@gmail.com> wrote:
> > 
> > On Wed, May 31, 2017 at 10:01 PM, Will Schmidt
> > <will_schmidt@vnet.ibm.com> wrote:
> >> Hi,
> >> 
> >> Add support for early expansion of vector shifts.  Including
> >> vec_sl (shift left), vec_sr (shift right), vec_sra (shift
> >> right algebraic), vec_rl (rotate left).
> >> Part of this includes adding the vector shift right instructions to
> >> the list of those instructions having an unsigned second argument.
> >> 
> >> The VSR (vector shift right) folding is a bit more complex than
> >> the others. This is due to requiring arg0 be unsigned for an algebraic
> >> shift before the gimple RSHIFT_EXPR assignment is built.
> > 
> > Jakub, do we sanitize that undefinedness of left shifts of negative values
> > and/or overflow of left shift of nonnegative values?


On Thu, 2017-06-01 at 10:17 +0200, Jakub Jelinek wrote:
> We don't yet, see PR77823 - all I've managed to do before stage1 was over
> was instrumentation of signed arithmetic integer overflow on vectors,
> division, shift etc. are tasks maybe for this stage1.
> 
> That said, shift instrumentation in particular is done early because every
> FE has different rules, and so if it is coming from target builtins that are
> folded into something, it wouldn't be instrumented anyway. 


On Thu, 2017-06-01 at 10:15 -0500, Bill Schmidt wrote:
> > 
> > Will, how is that defined in the intrinsics operation?  It might need similar
> > treatment as the abs case.
> 
> Answering for Will -- vec_sl is defined to simply shift bits off the end to the
> left and fill with zeros from the right, regardless of whether the source type
> is signed or unsigned.  The result type is signed iff the source type is
> signed.  So a negative value can become positive as a result of the
> operation.
> 
> The same is true of vec_rl, which will naturally rotate bits regardless of 
> signedness.


> > 
> > [I'd rather make the negative left shift case implementation defined
> > given C and C++ standards
> > do not agree to 100% AFAIK]

With the above answers, how does this one stand?

[ I have no issue adding the TYPE_OVERFLOW_WRAPS logic to treat some of
the cases differently, I'm just unclear on whether none/some/all of the
shifts will require that logic.  :-) ]

thanks,
-Will




> > 
> > Richard.
> > 
> >> [gcc]
> >> 
> >> 2017-05-26  Will Schmidt  <will_schmidt@vnet.ibm.com>
> >> 
> >>        * config/rs6000/rs6000.c (rs6000_gimple_fold_builtin): Add handling
> >>        for early expansion of vector shifts (sl,sr,sra,rl).
> >>        (builtin_function_type): Add vector shift right instructions
> >>        to the unsigned argument list.
> >> 
> >> [gcc/testsuite]
> >> 
> >> 2017-05-26  Will Schmidt  <will_schmidt@vnet.ibm.com>
> >> 
> >>        * testsuite/gcc.target/powerpc/fold-vec-shift-char.c: New.
> >>        * testsuite/gcc.target/powerpc/fold-vec-shift-int.c: New.
> >>        * testsuite/gcc.target/powerpc/fold-vec-shift-longlong.c: New.
> >>        * testsuite/gcc.target/powerpc/fold-vec-shift-short.c: New.
> >> 
> >> diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
> >> index 8adbc06..6ee0bfd 100644
> >> --- a/gcc/config/rs6000/rs6000.c
> >> +++ b/gcc/config/rs6000/rs6000.c
> >> @@ -17408,6 +17408,76 @@ rs6000_gimple_fold_builtin (gimple_stmt_iterator *gsi)
> >>        gsi_replace (gsi, g, true);
> >>        return true;
> >>       }
> >> +    /* Flavors of vec_rotate_left . */
> >> +    case ALTIVEC_BUILTIN_VRLB:
> >> +    case ALTIVEC_BUILTIN_VRLH:
> >> +    case ALTIVEC_BUILTIN_VRLW:
> >> +    case P8V_BUILTIN_VRLD:
> >> +      {
> >> +       arg0 = gimple_call_arg (stmt, 0);
> >> +       arg1 = gimple_call_arg (stmt, 1);
> >> +       lhs = gimple_call_lhs (stmt);
> >> +       gimple *g = gimple_build_assign (lhs, LROTATE_EXPR, arg0, arg1);
> >> +       gimple_set_location (g, gimple_location (stmt));
> >> +       gsi_replace (gsi, g, true);
> >> +       return true;
> >> +      }
> >> +  /* Flavors of vector shift right algebraic.  vec_sra{b,h,w} -> vsra{b,h,w}. */
> >> +    case ALTIVEC_BUILTIN_VSRAB:
> >> +    case ALTIVEC_BUILTIN_VSRAH:
> >> +    case ALTIVEC_BUILTIN_VSRAW:
> >> +    case P8V_BUILTIN_VSRAD:
> >> +      {
> >> +       arg0 = gimple_call_arg (stmt, 0);
> >> +       arg1 = gimple_call_arg (stmt, 1);
> >> +       lhs = gimple_call_lhs (stmt);
> >> +       gimple *g = gimple_build_assign (lhs, RSHIFT_EXPR, arg0, arg1);
> >> +       gimple_set_location (g, gimple_location (stmt));
> >> +       gsi_replace (gsi, g, true);
> >> +       return true;
> >> +      }
> >> +   /* Flavors of vector shift left.  builtin_altivec_vsl{b,h,w} -> vsl{b,h,w}.  */
> >> +    case ALTIVEC_BUILTIN_VSLB:
> >> +    case ALTIVEC_BUILTIN_VSLH:
> >> +    case ALTIVEC_BUILTIN_VSLW:
> >> +    case P8V_BUILTIN_VSLD:
> >> +      {
> >> +       arg0 = gimple_call_arg (stmt, 0);
> >> +       arg1 = gimple_call_arg (stmt, 1);
> >> +       lhs = gimple_call_lhs (stmt);
> >> +       gimple *g = gimple_build_assign (lhs, LSHIFT_EXPR, arg0, arg1);
> >> +       gimple_set_location (g, gimple_location (stmt));
> >> +       gsi_replace (gsi, g, true);
> >> +       return true;
> >> +      }
> >> +    /* Flavors of vector shift right. */
> >> +    case ALTIVEC_BUILTIN_VSRB:
> >> +    case ALTIVEC_BUILTIN_VSRH:
> >> +    case ALTIVEC_BUILTIN_VSRW:
> >> +    case P8V_BUILTIN_VSRD:
> >> +      {
> >> +       arg0 = gimple_call_arg (stmt, 0);
> >> +       arg1 = gimple_call_arg (stmt, 1);
> >> +       lhs = gimple_call_lhs (stmt);
> >> +       gimple *g;
> >> +       /* convert arg0 to unsigned */
> >> +       arg0 = convert(unsigned_type_for(TREE_TYPE(arg0)),arg0);
> >> +       tree arg0_uns = create_tmp_reg_or_ssa_name(unsigned_type_for(TREE_TYPE(arg0)));
> >> +       g = gimple_build_assign(arg0_uns,arg0);
> >> +       gimple_set_location (g, gimple_location (stmt));
> >> +       gsi_insert_before (gsi, g, GSI_SAME_STMT);
> >> +       /* convert lhs to unsigned and do the shift.  */
> >> +       tree lhs_uns = create_tmp_reg_or_ssa_name(unsigned_type_for(TREE_TYPE(lhs)));
> >> +       g = gimple_build_assign (lhs_uns, RSHIFT_EXPR, arg0_uns, arg1);
> >> +       gimple_set_location (g, gimple_location (stmt));
> >> +       gsi_insert_before (gsi, g, GSI_SAME_STMT);
> >> +       /* convert lhs back to a signed type for the return. */
> >> +       lhs_uns = convert(signed_type_for(TREE_TYPE(lhs)),lhs_uns);
> >> +       g = gimple_build_assign(lhs,lhs_uns);
> >> +       gimple_set_location (g, gimple_location (stmt));
> >> +       gsi_replace (gsi, g, true);
> >> +       return true;
> >> +      }
> >>     default:
> >>       break;
> >>     }
> >> @@ -19128,6 +19198,14 @@ builtin_function_type (machine_mode mode_ret, machine_mode mode_arg0,
> >>       h.uns_p[2] = 1;
> >>       break;
> >> 
> >> +       /* unsigned second arguments (vector shift right).  */
> >> +    case ALTIVEC_BUILTIN_VSRB:
> >> +    case ALTIVEC_BUILTIN_VSRH:
> >> +    case ALTIVEC_BUILTIN_VSRW:
> >> +    case P8V_BUILTIN_VSRD:
> >> +      h.uns_p[2] = 1;
> >> +      break;
> >> +
> >>     default:
> >>       break;
> >>     }
> >> diff --git a/gcc/testsuite/gcc.target/powerpc/fold-vec-shift-char.c b/gcc/testsuite/gcc.target/powerpc/fold-vec-shift-char.c
> >> new file mode 100644
> >> index 0000000..ebe91e7
> >> --- /dev/null
> >> +++ b/gcc/testsuite/gcc.target/powerpc/fold-vec-shift-char.c
> >> @@ -0,0 +1,66 @@
> >> +/* Verify that overloaded built-ins for vec_sl with char
> >> +   inputs produce the right results.  */
> >> +
> >> +/* { dg-do compile } */
> >> +/* { dg-require-effective-target powerpc_altivec_ok } */
> >> +/* { dg-options "-maltivec -O2" } */
> >> +
> >> +#include <altivec.h>
> >> +
> >> +//# vec_sl  - shift left
> >> +//# vec_sr  - shift right
> >> +//# vec_sra - shift right algebraic
> >> +//# vec_rl  - rotate left
> >> +
> >> +vector signed char
> >> +testsl_signed (vector signed char x, vector unsigned char y)
> >> +{
> >> +  return vec_sl (x, y);
> >> +}
> >> +
> >> +vector unsigned char
> >> +testsl_unsigned (vector unsigned char x, vector unsigned char y)
> >> +{
> >> +  return vec_sl (x, y);
> >> +}
> >> +
> >> +vector signed char
> >> +testsr_signed (vector signed char x, vector unsigned char y)
> >> +{
> >> +  return vec_sr (x, y);
> >> +}
> >> +
> >> +vector unsigned char
> >> +testsr_unsigned (vector unsigned char x, vector unsigned char y)
> >> +{
> >> +  return vec_sr (x, y);
> >> +}
> >> +
> >> +vector signed char
> >> +testsra_signed (vector signed char x, vector unsigned char y)
> >> +{
> >> +  return vec_sra (x, y);
> >> +}
> >> +
> >> +vector unsigned char
> >> +testsra_unsigned (vector unsigned char x, vector unsigned char y)
> >> +{
> >> +  return vec_sra (x, y);
> >> +}
> >> +
> >> +vector signed char
> >> +testrl_signed (vector signed char x, vector unsigned char y)
> >> +{
> >> +  return vec_rl (x, y);
> >> +}
> >> +
> >> +vector unsigned char
> >> +testrl_unsigned (vector unsigned char x, vector unsigned char y)
> >> +{
> >> +  return vec_rl (x, y);
> >> +}
> >> +
> >> +/* { dg-final { scan-assembler-times "vslb" 2 } } */
> >> +/* { dg-final { scan-assembler-times "vsrb" 2 } } */
> >> +/* { dg-final { scan-assembler-times "vsrab" 2 } } */
> >> +/* { dg-final { scan-assembler-times "vrlb" 2 } } */
> >> diff --git a/gcc/testsuite/gcc.target/powerpc/fold-vec-shift-int.c b/gcc/testsuite/gcc.target/powerpc/fold-vec-shift-int.c
> >> new file mode 100644
> >> index 0000000..e9c5fe1
> >> --- /dev/null
> >> +++ b/gcc/testsuite/gcc.target/powerpc/fold-vec-shift-int.c
> >> @@ -0,0 +1,61 @@
> >> +/* Verify that overloaded built-ins for vec_sl with int
> >> +   inputs produce the right results.  */
> >> +
> >> +/* { dg-do compile } */
> >> +/* { dg-require-effective-target powerpc_altivec_ok } */
> >> +/* { dg-options "-maltivec -O2" } */
> >> +
> >> +#include <altivec.h>
> >> +
> >> +vector signed int
> >> +testsl_signed (vector signed int x, vector unsigned int y)
> >> +{
> >> +  return vec_sl (x, y);
> >> +}
> >> +
> >> +vector unsigned int
> >> +testsl_unsigned (vector unsigned int x, vector unsigned int y)
> >> +{
> >> +  return vec_sl (x, y);
> >> +}
> >> +
> >> +vector signed int
> >> +testsr_signed (vector signed int x, vector unsigned int y)
> >> +{
> >> +  return vec_sr (x, y);
> >> +}
> >> +
> >> +vector unsigned int
> >> +testsr_unsigned (vector unsigned int x, vector unsigned int y)
> >> +{
> >> +  return vec_sr (x, y);
> >> +}
> >> +
> >> +vector signed int
> >> +testsra_signed (vector signed int x, vector unsigned int y)
> >> +{
> >> +  return vec_sra (x, y);
> >> +}
> >> +
> >> +vector unsigned int
> >> +testsra_unsigned (vector unsigned int x, vector unsigned int y)
> >> +{
> >> +  return vec_sra (x, y);
> >> +}
> >> +
> >> +vector signed int
> >> +testrl_signed (vector signed int x, vector unsigned int y)
> >> +{
> >> +  return vec_rl (x, y);
> >> +}
> >> +
> >> +vector unsigned int
> >> +testrl_unsigned (vector unsigned int x, vector unsigned int y)
> >> +{
> >> +  return vec_rl (x, y);
> >> +}
> >> +
> >> +/* { dg-final { scan-assembler-times "vslw" 2 } } */
> >> +/* { dg-final { scan-assembler-times "vsrw" 2 } } */
> >> +/* { dg-final { scan-assembler-times "vsraw" 2 } } */
> >> +/* { dg-final { scan-assembler-times "vrlw" 2 } } */
> >> diff --git a/gcc/testsuite/gcc.target/powerpc/fold-vec-shift-longlong.c b/gcc/testsuite/gcc.target/powerpc/fold-vec-shift-longlong.c
> >> new file mode 100644
> >> index 0000000..97b82cf
> >> --- /dev/null
> >> +++ b/gcc/testsuite/gcc.target/powerpc/fold-vec-shift-longlong.c
> >> @@ -0,0 +1,63 @@
> >> +/* Verify that overloaded built-ins for vec_sl with long long
> >> +   inputs produce the right results.  */
> >> +
> >> +/* { dg-do compile } */
> >> +/* { dg-require-effective-target powerpc_p8vector_ok } */
> >> +/* { dg-options "-mpower8-vector -O2" } */
> >> +
> >> +#include <altivec.h>
> >> +
> >> +vector signed long long
> >> +testsl_signed (vector signed long long x, vector unsigned long long y)
> >> +{
> >> +  return vec_sl (x, y);
> >> +}
> >> +
> >> +vector unsigned long long
> >> +testsl_unsigned (vector unsigned long long x, vector unsigned long long y)
> >> +{
> >> +  return vec_sl (x, y);
> >> +}
> >> +
> >> +vector signed long long
> >> +testsr_signed (vector signed long long x, vector unsigned long long y)
> >> +{
> >> +  return vec_sr (x, y);
> >> +}
> >> +
> >> +vector unsigned long long
> >> +testsr_unsigned (vector unsigned long long x, vector unsigned long long y)
> >> +{
> >> +  return vec_sr (x, y);
> >> +}
> >> +
> >> +vector signed long long
> >> +testsra_signed (vector signed long long x, vector unsigned long long y)
> >> +{
> >> +  return vec_sra (x, y);
> >> +}
> >> +
> >> +/* watch for PR 79544 here (vsrd / vsrad issue) */
> >> +vector unsigned long long
> >> +testsra_unsigned (vector unsigned long long x, vector unsigned long long y)
> >> +{
> >> +  return vec_sra (x, y);
> >> +}
> >> +
> >> +vector signed long long
> >> +testrl_signed (vector signed long long x, vector unsigned long long y)
> >> +{
> >> +  return vec_rl (x, y);
> >> +}
> >> +
> >> +vector unsigned long long
> >> +testrl_unsigned (vector unsigned long long x, vector unsigned long long y)
> >> +{
> >> +  return vec_rl (x, y);
> >> +}
> >> +
> >> +/* { dg-final { scan-assembler-times "vsld" 2 } } */
> >> +/* { dg-final { scan-assembler-times "vsrd" 2 } } */
> >> +/* { dg-final { scan-assembler-times "vsrad" 2 } } */
> >> +/* { dg-final { scan-assembler-times "vrld" 2 } } */
> >> +
> >> diff --git a/gcc/testsuite/gcc.target/powerpc/fold-vec-shift-short.c b/gcc/testsuite/gcc.target/powerpc/fold-vec-shift-short.c
> >> new file mode 100644
> >> index 0000000..4ca7c18
> >> --- /dev/null
> >> +++ b/gcc/testsuite/gcc.target/powerpc/fold-vec-shift-short.c
> >> @@ -0,0 +1,61 @@
> >> +/* Verify that overloaded built-ins for vec_sl with short
> >> +   inputs produce the right results.  */
> >> +
> >> +/* { dg-do compile } */
> >> +/* { dg-require-effective-target powerpc_altivec_ok } */
> >> +/* { dg-options "-maltivec -O2" } */
> >> +
> >> +#include <altivec.h>
> >> +
> >> +vector signed short
> >> +testsl_signed (vector signed short x, vector unsigned short y)
> >> +{
> >> +  return vec_sl (x, y);
> >> +}
> >> +
> >> +vector unsigned short
> >> +testsl_unsigned (vector unsigned short x, vector unsigned short y)
> >> +{
> >> +  return vec_sl (x, y);
> >> +}
> >> +
> >> +vector signed short
> >> +testsr_signed (vector signed short x, vector unsigned short y)
> >> +{
> >> +  return vec_sr (x, y);
> >> +}
> >> +
> >> +vector unsigned short
> >> +testsr_unsigned (vector unsigned short x, vector unsigned short y)
> >> +{
> >> +  return vec_sr (x, y);
> >> +}
> >> +
> >> +vector signed short
> >> +testsra_signed (vector signed short x, vector unsigned short y)
> >> +{
> >> +  return vec_sra (x, y);
> >> +}
> >> +
> >> +vector unsigned short
> >> +testsra_unsigned (vector unsigned short x, vector unsigned short y)
> >> +{
> >> +  return vec_sra (x, y);
> >> +}
> >> +
> >> +vector signed short
> >> +testrl_signed (vector signed short x, vector unsigned short y)
> >> +{
> >> +  return vec_rl (x, y);
> >> +}
> >> +
> >> +vector unsigned short
> >> +testrl_unsigned (vector unsigned short x, vector unsigned short y)
> >> +{
> >> +  return vec_rl (x, y);
> >> +}
> >> +
> >> +/* { dg-final { scan-assembler-times "vslh" 2 } } */
> >> +/* { dg-final { scan-assembler-times "vsrh" 2 } } */
> >> +/* { dg-final { scan-assembler-times "vsrah" 2 } } */
> >> +/* { dg-final { scan-assembler-times "vrlh" 2 } } */
> >> 
> >> 
> >> 
> > 
>