[x86] set default reciprocal (division and square root) codegen to match GCC

D8982 ( checked in at http://reviews.llvm.org/rL239001 ) added command-line
options to allow reciprocal estimate instructions to be used in place of
divisions and square roots.

This patch changes the default settings for x86 targets to allow that recip
codegen (except for scalar division because that breaks too much code) when
using -ffast-math or its equivalent.

This matches GCC behavior for this kind of codegen.

Differential Revision: http://reviews.llvm.org/D10396

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240310 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86TargetMachine.cpp b/lib/Target/X86/X86TargetMachine.cpp
index 3d6eb4f7ce02957b55185c826536bc2e6cabc9b3..fb9cb4ba4c86edf8c0c9158fab35d1935b38265e 100644 (file)
--- a/lib/Target/X86/X86TargetMachine.cpp
+++ b/lib/Target/X86/X86TargetMachine.cpp
@@ -110,12 +110,15 @@ X86TargetMachine::X86TargetMachine(const Target &T, const Triple &TT,
   if (Subtarget.isTargetWin64())
     this->Options.TrapUnreachable = true;
 
-  // TODO: By default, all reciprocal estimate operations are off because
-  // that matches the behavior before TargetRecip was added (except for btver2
-  // which used subtarget features to enable this type of codegen).
-  // We should change this to match GCC behavior where everything but
-  // scalar division estimates are turned on by default with -ffast-math.
-  this->Options.Reciprocals.setDefaults("all", false, 1);
+  // By default (and when -ffast-math is on), enable estimate codegen for
+  // everything except scalar division. By default, use 1 refinement step for
+  // all operations. Defaults may be overridden by using command-line options.
+  // Scalar division estimates are disabled because they break too much
+  // real-world code. These defaults match GCC behavior.
+  this->Options.Reciprocals.setDefaults("sqrtf", true, 1);
+  this->Options.Reciprocals.setDefaults("divf", false, 1);
+  this->Options.Reciprocals.setDefaults("vec-sqrtf", true, 1);
+  this->Options.Reciprocals.setDefaults("vec-divf", true, 1);
 
   initAsmInfo();
 }

diff --git a/test/CodeGen/X86/recip-fastmath.ll b/test/CodeGen/X86/recip-fastmath.ll
index 7f1521a83bcfdeadd0ec1e1fd4a2e1d6cfcc3d8a..8e02dad9d5aeeea54a9fa94f46cca2f548442e21 100644 (file)
--- a/test/CodeGen/X86/recip-fastmath.ll
+++ b/test/CodeGen/X86/recip-fastmath.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s -mtriple=x86_64-unknown-unknown -mattr=sse2 | FileCheck %s
+; RUN: llc < %s -mtriple=x86_64-unknown-unknown -mattr=sse2 -recip=!divf,!vec-divf | FileCheck %s --check-prefix=NORECIP
 ; RUN: llc < %s -mtriple=x86_64-unknown-unknown -mattr=avx -recip=divf,vec-divf | FileCheck %s --check-prefix=RECIP
 ; RUN: llc < %s -mtriple=x86_64-unknown-unknown -mattr=avx -recip=divf:2,vec-divf:2 | FileCheck %s --check-prefix=REFINE
 
@@ -14,11 +14,11 @@ define float @reciprocal_estimate(float %x) #0 {
   %div = fdiv fast float 1.0, %x
   ret float %div
 
-; CHECK-LABEL: reciprocal_estimate:
-; CHECK: movss
-; CHECK-NEXT: divss
-; CHECK-NEXT: movaps
-; CHECK-NEXT: retq
+; NORECIP-LABEL: reciprocal_estimate:
+; NORECIP: movss
+; NORECIP-NEXT: divss
+; NORECIP-NEXT: movaps
+; NORECIP-NEXT: retq
 
 ; RECIP-LABEL: reciprocal_estimate:
 ; RECIP: vrcpss
@@ -45,11 +45,11 @@ define <4 x float> @reciprocal_estimate_v4f32(<4 x float> %x) #0 {
   %div = fdiv fast <4 x float> <float 1.0, float 1.0, float 1.0, float 1.0>, %x
   ret <4 x float> %div
 
-; CHECK-LABEL: reciprocal_estimate_v4f32:
-; CHECK: movaps
-; CHECK-NEXT: divps
-; CHECK-NEXT: movaps
-; CHECK-NEXT: retq
+; NORECIP-LABEL: reciprocal_estimate_v4f32:
+; NORECIP: movaps
+; NORECIP-NEXT: divps
+; NORECIP-NEXT: movaps
+; NORECIP-NEXT: retq
 
 ; RECIP-LABEL: reciprocal_estimate_v4f32:
 ; RECIP: vrcpps
@@ -76,14 +76,14 @@ define <8 x float> @reciprocal_estimate_v8f32(<8 x float> %x) #0 {
   %div = fdiv fast <8 x float> <float 1.0, float 1.0, float 1.0, float 1.0, float 1.0, float 1.0, float 1.0, float 1.0>, %x
   ret <8 x float> %div
 
-; CHECK-LABEL: reciprocal_estimate_v8f32:
-; CHECK: movaps
-; CHECK: movaps
-; CHECK-NEXT: divps
-; CHECK-NEXT: divps
-; CHECK-NEXT: movaps
-; CHECK-NEXT: movaps
-; CHECK-NEXT: retq
+; NORECIP-LABEL: reciprocal_estimate_v8f32:
+; NORECIP: movaps
+; NORECIP: movaps
+; NORECIP-NEXT: divps
+; NORECIP-NEXT: divps
+; NORECIP-NEXT: movaps
+; NORECIP-NEXT: movaps
+; NORECIP-NEXT: retq
 
 ; RECIP-LABEL: reciprocal_estimate_v8f32:
 ; RECIP: vrcpps

diff --git a/test/CodeGen/X86/sqrt-fastmath.ll b/test/CodeGen/X86/sqrt-fastmath.ll
index 373fa53c970f86ad1176c114489f9dba8fac23bc..0f8d9f4d713fae17c12caaaddf66c5cf8d9c44e0 100644 (file)
--- a/test/CodeGen/X86/sqrt-fastmath.ll
+++ b/test/CodeGen/X86/sqrt-fastmath.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s -mtriple=x86_64-unknown-unknown -mattr=sse2 | FileCheck %s
+; RUN: llc < %s -mtriple=x86_64-unknown-unknown -mattr=sse2 -recip=!sqrtf,!vec-sqrtf,!divf,!vec-divf | FileCheck %s --check-prefix=NORECIP
 ; RUN: llc < %s -mtriple=x86_64-unknown-unknown -mattr=avx -recip=sqrtf,vec-sqrtf | FileCheck %s --check-prefix=ESTIMATE
 
 declare double @__sqrt_finite(double) #0
@@ -10,10 +10,10 @@ declare <8 x float> @llvm.sqrt.v8f32(<8 x float>) #0
 
 
 define double @fd(double %d) #0 {
-; CHECK-LABEL: fd:
-; CHECK:       # BB#0:
-; CHECK-NEXT:    sqrtsd %xmm0, %xmm0
-; CHECK-NEXT:    retq
+; NORECIP-LABEL: fd:
+; NORECIP:       # BB#0:
+; NORECIP-NEXT:    sqrtsd %xmm0, %xmm0
+; NORECIP-NEXT:    retq
 ;
 ; ESTIMATE-LABEL: fd:
 ; ESTIMATE:       # BB#0:
@@ -25,10 +25,10 @@ define double @fd(double %d) #0 {
 
 
 define float @ff(float %f) #0 {
-; CHECK-LABEL: ff:
-; CHECK:       # BB#0:
-; CHECK-NEXT:    sqrtss %xmm0, %xmm0
-; CHECK-NEXT:    retq
+; NORECIP-LABEL: ff:
+; NORECIP:       # BB#0:
+; NORECIP-NEXT:    sqrtss %xmm0, %xmm0
+; NORECIP-NEXT:    retq
 ;
 ; ESTIMATE-LABEL: ff:
 ; ESTIMATE:       # BB#0:
@@ -49,11 +49,11 @@ define float @ff(float %f) #0 {
 
 
 define x86_fp80 @fld(x86_fp80 %ld) #0 {
-; CHECK-LABEL: fld:
-; CHECK:       # BB#0:
-; CHECK-NEXT:    fldt {{[0-9]+}}(%rsp)
-; CHECK-NEXT:    fsqrt
-; CHECK-NEXT:    retq
+; NORECIP-LABEL: fld:
+; NORECIP:       # BB#0:
+; NORECIP-NEXT:    fldt {{[0-9]+}}(%rsp)
+; NORECIP-NEXT:    fsqrt
+; NORECIP-NEXT:    retq
 ;
 ; ESTIMATE-LABEL: fld:
 ; ESTIMATE:       # BB#0:
@@ -67,12 +67,12 @@ define x86_fp80 @fld(x86_fp80 %ld) #0 {
 
 
 define float @reciprocal_square_root(float %x) #0 {
-; CHECK-LABEL: reciprocal_square_root:
-; CHECK:       # BB#0:
-; CHECK-NEXT:    sqrtss %xmm0, %xmm1
-; CHECK-NEXT:    movss {{.*#+}} xmm0 = mem[0],zero,zero,zero
-; CHECK-NEXT:    divss %xmm1, %xmm0
-; CHECK-NEXT:    retq
+; NORECIP-LABEL: reciprocal_square_root:
+; NORECIP:       # BB#0:
+; NORECIP-NEXT:    sqrtss %xmm0, %xmm1
+; NORECIP-NEXT:    movss {{.*#+}} xmm0 = mem[0],zero,zero,zero
+; NORECIP-NEXT:    divss %xmm1, %xmm0
+; NORECIP-NEXT:    retq
 ;
 ; ESTIMATE-LABEL: reciprocal_square_root:
 ; ESTIMATE:       # BB#0:
@@ -89,12 +89,12 @@ define float @reciprocal_square_root(float %x) #0 {
 }
 
 define <4 x float> @reciprocal_square_root_v4f32(<4 x float> %x) #0 {
-; CHECK-LABEL: reciprocal_square_root_v4f32:
-; CHECK:       # BB#0:
-; CHECK-NEXT:    sqrtps %xmm0, %xmm1
-; CHECK-NEXT:    movaps {{.*#+}} xmm0 = [1.000000e+00,1.000000e+00,1.000000e+00,1.000000e+00]
-; CHECK-NEXT:    divps %xmm1, %xmm0
-; CHECK-NEXT:    retq
+; NORECIP-LABEL: reciprocal_square_root_v4f32:
+; NORECIP:       # BB#0:
+; NORECIP-NEXT:    sqrtps %xmm0, %xmm1
+; NORECIP-NEXT:    movaps {{.*#+}} xmm0 = [1.000000e+00,1.000000e+00,1.000000e+00,1.000000e+00]
+; NORECIP-NEXT:    divps %xmm1, %xmm0
+; NORECIP-NEXT:    retq
 ;
 ; ESTIMATE-LABEL: reciprocal_square_root_v4f32:
 ; ESTIMATE:       # BB#0:
@@ -111,15 +111,15 @@ define <4 x float> @reciprocal_square_root_v4f32(<4 x float> %x) #0 {
 }
 
 define <8 x float> @reciprocal_square_root_v8f32(<8 x float> %x) #0 {
-; CHECK-LABEL: reciprocal_square_root_v8f32:
-; CHECK:       # BB#0:
-; CHECK-NEXT:    sqrtps %xmm1, %xmm2
-; CHECK-NEXT:    sqrtps %xmm0, %xmm3
-; CHECK-NEXT:    movaps {{.*#+}} xmm1 = [1.000000e+00,1.000000e+00,1.000000e+00,1.000000e+00]
-; CHECK-NEXT:    movaps %xmm1, %xmm0
-; CHECK-NEXT:    divps %xmm3, %xmm0
-; CHECK-NEXT:    divps %xmm2, %xmm1
-; CHECK-NEXT:    retq
+; NORECIP-LABEL: reciprocal_square_root_v8f32:
+; NORECIP:       # BB#0:
+; NORECIP-NEXT:    sqrtps %xmm1, %xmm2
+; NORECIP-NEXT:    sqrtps %xmm0, %xmm3
+; NORECIP-NEXT:    movaps {{.*#+}} xmm1 = [1.000000e+00,1.000000e+00,1.000000e+00,1.000000e+00]
+; NORECIP-NEXT:    movaps %xmm1, %xmm0
+; NORECIP-NEXT:    divps %xmm3, %xmm0
+; NORECIP-NEXT:    divps %xmm2, %xmm1
+; NORECIP-NEXT:    retq
 ;
 ; ESTIMATE-LABEL: reciprocal_square_root_v8f32:
 ; ESTIMATE:       # BB#0: