[PATCH] Convert sqrt functions into sqrt instructions when -ffast-math is in effect

[Chad Rosier]

LGTM.

 Chad

On May 24, 2013, at 12:54 PM, Preston Gurd <preston.gurd at intel.com> wrote:

> Hi nadav, chandlerc,
> 
> When -ffast-math is in effect (on Linux, at least), clang defines __FINITE_MATH_ONLY__ > 0 when including <math.h>. This causes the preprocessor to include <bits/math-finite.h>, which renames the sqrt functions. For instance, "sqrt" is renamed as "__sqrt_finite". 
> 
> This patch adds the 3 new names in such a way that they will be treated as equivalent to their respective original names.
> 
> 
> http://llvm-reviews.chandlerc.com/D863
> 
> Files:
>  include/llvm/Target/TargetLibraryInfo.h
>  lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
>  lib/Target/TargetLibraryInfo.cpp
>  test/CodeGen/X86/sqrt-fastmath.ll
> 
> Index: include/llvm/Target/TargetLibraryInfo.h
> ===================================================================
> --- include/llvm/Target/TargetLibraryInfo.h
> +++ include/llvm/Target/TargetLibraryInfo.h
> @@ -57,6 +57,12 @@
>       dunder_isoc99_sscanf,
>       /// void *__memcpy_chk(void *s1, const void *s2, size_t n, size_t s1size);
>       memcpy_chk,
> +      /// double __sqrt_finite(double x);
> +      sqrt_finite,
> +      /// float __sqrt_finite(float x);
> +      sqrtf_finite,
> +      /// long double __sqrt_finite(long double x);
> +      sqrtl_finite,
>       /// char * __strdup(const char *s);
>       dunder_strdup,
>       /// char *__strndup(const char *s, size_t n);
> @@ -677,6 +683,8 @@
>     case LibFunc::sin:       case LibFunc::sinf:       case LibFunc::sinl:
>     case LibFunc::cos:       case LibFunc::cosf:       case LibFunc::cosl:
>     case LibFunc::sqrt:      case LibFunc::sqrtf:      case LibFunc::sqrtl:
> +    case LibFunc::sqrt_finite: case LibFunc::sqrtf_finite:
> +                                                  case LibFunc::sqrtl_finite:
>     case LibFunc::floor:     case LibFunc::floorf:     case LibFunc::floorl:
>     case LibFunc::nearbyint: case LibFunc::nearbyintf: case LibFunc::nearbyintl:
>     case LibFunc::ceil:      case LibFunc::ceilf:      case LibFunc::ceill:
> Index: lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
> ===================================================================
> --- lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
> +++ lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
> @@ -5593,6 +5593,9 @@
>       case LibFunc::sqrt:
>       case LibFunc::sqrtf:
>       case LibFunc::sqrtl:
> +      case LibFunc::sqrt_finite:
> +      case LibFunc::sqrtf_finite:
> +      case LibFunc::sqrtl_finite:
>         if (visitUnaryFloatCall(I, ISD::FSQRT))
>           return;
>         break;
> Index: lib/Target/TargetLibraryInfo.cpp
> ===================================================================
> --- lib/Target/TargetLibraryInfo.cpp
> +++ lib/Target/TargetLibraryInfo.cpp
> @@ -43,6 +43,9 @@
>     "__isoc99_scanf",
>     "__isoc99_sscanf",
>     "__memcpy_chk",
> +    "__sqrt_finite",
> +    "__sqrtf_finite",
> +    "__sqrtl_finite",
>     "__strdup",
>     "__strndup",
>     "__strtok_r",
> Index: test/CodeGen/X86/sqrt-fastmath.ll
> ===================================================================
> --- /dev/null
> +++ test/CodeGen/X86/sqrt-fastmath.ll
> @@ -0,0 +1,60 @@
> +; RUN: llc < %s -mcpu=core2 | FileCheck %s
> +
> +; generated using "clang -S -O2 -ffast-math -emit-llvm sqrt.c" from
> +; #include <math.h>
> +; 
> +; double fd(double d){
> +;   return sqrt(d);
> +; }
> +; 
> +; float ff(float f){
> +;   return sqrtf(f);
> +; }
> +; 
> +; long double fld(long double ld){
> +;   return sqrtl(ld);
> +; }
> +;
> +; Tests conversion of sqrt function calls into sqrt instructions when
> +; -ffast-math is in effect.
> +
> +; ModuleID = 'sqrt.c'
> +target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
> +target triple = "x86_64-unknown-linux-gnu"
> +
> +; Function Attrs: nounwind readnone uwtable
> +define double @fd(double %d) #0 {
> +entry:
> +; CHECK: sqrtsd
> +  %call = tail call double @__sqrt_finite(double %d) #2
> +  ret double %call
> +}
> +
> +; Function Attrs: nounwind readnone
> +declare double @__sqrt_finite(double) #1
> +
> +; Function Attrs: nounwind readnone uwtable
> +define float @ff(float %f) #0 {
> +entry:
> +; CHECK: sqrtss
> +  %call = tail call float @__sqrtf_finite(float %f) #2
> +  ret float %call
> +}
> +
> +; Function Attrs: nounwind readnone
> +declare float @__sqrtf_finite(float) #1
> +
> +; Function Attrs: nounwind readnone uwtable
> +define x86_fp80 @fld(x86_fp80 %ld) #0 {
> +entry:
> +; CHECK: fsqrt
> +  %call = tail call x86_fp80 @__sqrtl_finite(x86_fp80 %ld) #2
> +  ret x86_fp80 %call
> +}
> +
> +; Function Attrs: nounwind readnone
> +declare x86_fp80 @__sqrtl_finite(x86_fp80) #1
> +
> +attributes #0 = { nounwind readnone uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-frame-pointer-elim-non-leaf"="false" "no-infs-fp-math"="true" "no-nans-fp-math"="true" "unsafe-fp-math"="true" "use-soft-float"="false" }
> +attributes #1 = { nounwind readnone "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-frame-pointer-elim-non-leaf"="false" "no-infs-fp-math"="true" "no-nans-fp-math"="true" "unsafe-fp-math"="true" "use-soft-float"="false" }
> +attributes #2 = { nounwind readnone }
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