[SimplifyLibCalls] Propagate fast math flags while optimizing pow().

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@291577 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Utils/SimplifyLibCalls.cpp

@@ -1139,6 +1139,10 @@ Value *LibCallSimplifier::optimizePow(CallInst *CI, IRBuilder<> &B) {
         !V.isInteger())
       return nullptr;
 
+    // Propagate fast math flags.
+    IRBuilder<>::FastMathFlagGuard Guard(B);
+    B.setFastMathFlags(CI->getFastMathFlags());
+
     // We will memoize intermediate products of the Addition Chain.
     Value *InnerChain[33] = {nullptr};
     InnerChain[1] = Op1;
@@ -1149,7 +1153,6 @@ Value *LibCallSimplifier::optimizePow(CallInst *CI, IRBuilder<> &B) {
     bool ignored;
     V.convert(APFloat::IEEEdouble(), APFloat::rmTowardZero, &ignored);
     
-    // TODO: Should the new instructions propagate the 'fast' flag of the pow()?
     Value *FMul = getPow(InnerChain, V.convertToDouble(), B);
     // For negative exponents simply compute the reciprocal.
     if (Op2C->isNegative())

test/Transforms/InstCombine/pow-4.ll

@@ -10,8 +10,8 @@ declare float @llvm.pow.f32(float, float)
 define float @test_simplify_4f(float %x) {
 ; CHECK-LABEL: @test_simplify_4f(
 ; CHECK-NOT: pow
-; CHECK-NEXT: %1 = fmul float %x, %x
-; CHECK-NEXT: %2 = fmul float %1, %1
+; CHECK-NEXT: %1 = fmul fast float %x, %x
+; CHECK-NEXT: %2 = fmul fast float %1, %1
 ; CHECK-NEXT: ret float %2
   %1 = call fast float @llvm.pow.f32(float %x, float 4.000000e+00)
   ret float %1
@@ -21,8 +21,8 @@ define float @test_simplify_4f(float %x) {
 define double @test_simplify_3(double %x) {
 ; CHECK-LABEL: @test_simplify_3(
 ; CHECK-NOT: pow
-; CHECK-NEXT: %1 = fmul double %x, %x
-; CHECK-NEXT: %2 = fmul double %1, %x
+; CHECK-NEXT: %1 = fmul fast double %x, %x
+; CHECK-NEXT: %2 = fmul fast double %1, %x
 ; CHECK-NEXT: ret double %2
   %1 = call fast double @llvm.pow.f64(double %x, double 3.000000e+00)
   ret double %1
@@ -32,8 +32,8 @@ define double @test_simplify_3(double %x) {
 define double @test_simplify_4(double %x) {
 ; CHECK-LABEL: @test_simplify_4(
 ; CHECK-NOT: pow
-; CHECK-NEXT: %1 = fmul double %x, %x
-; CHECK-NEXT: %2 = fmul double %1, %1
+; CHECK-NEXT: %1 = fmul fast double %x, %x
+; CHECK-NEXT: %2 = fmul fast double %1, %1
 ; CHECK-NEXT: ret double %2
   %1 = call fast double @llvm.pow.f64(double %x, double 4.000000e+00)
   ret double %1
@@ -43,11 +43,11 @@ define double @test_simplify_4(double %x) {
 define double @test_simplify_15(double %x) {
 ; CHECK-LABEL: @test_simplify_15(
 ; CHECK-NOT: pow
-; CHECK-NEXT: %1 = fmul double %x, %x
-; CHECK-NEXT: %2 = fmul double %1, %x
-; CHECK-NEXT: %3 = fmul double %2, %2
-; CHECK-NEXT: %4 = fmul double %3, %3
-; CHECK-NEXT: %5 = fmul double %2, %4
+; CHECK-NEXT: %1 = fmul fast double %x, %x
+; CHECK-NEXT: %2 = fmul fast double %1, %x
+; CHECK-NEXT: %3 = fmul fast double %2, %2
+; CHECK-NEXT: %4 = fmul fast double %3, %3
+; CHECK-NEXT: %5 = fmul fast double %2, %4
 ; CHECK-NEXT: ret double %5
   %1 = call fast double @llvm.pow.f64(double %x, double 1.500000e+01)
   ret double %1
@@ -57,11 +57,11 @@ define double @test_simplify_15(double %x) {
 define double @test_simplify_neg_7(double %x) {
 ; CHECK-LABEL: @test_simplify_neg_7(
 ; CHECK-NOT: pow
-; CHECK-NEXT: %1 = fmul double %x, %x
-; CHECK-NEXT: %2 = fmul double %1, %x
-; CHECK-NEXT: %3 = fmul double %1, %2
-; CHECK-NEXT: %4 = fmul double %1, %3
-; CHECK-NEXT: %5 = fdiv double 1.000000e+00, %4
+; CHECK-NEXT: %1 = fmul fast double %x, %x
+; CHECK-NEXT: %2 = fmul fast double %1, %1
+; CHECK-NEXT: %3 = fmul fast double %2, %x
+; CHECK-NEXT: %4 = fmul fast double %1, %3
+; CHECK-NEXT: %5 = fdiv fast double 1.000000e+00, %4
 ; CHECK-NEXT: ret double %5
   %1 = call fast double @llvm.pow.f64(double %x, double -7.000000e+00)
   ret double %1
@@ -71,13 +71,13 @@ define double @test_simplify_neg_7(double %x) {
 define double @test_simplify_neg_19(double %x) {
 ; CHECK-LABEL: @test_simplify_neg_19(
 ; CHECK-NOT: pow
-; CHECK-NEXT: %1 = fmul double %x, %x
-; CHECK-NEXT: %2 = fmul double %1, %1
-; CHECK-NEXT: %3 = fmul double %2, %2
-; CHECK-NEXT: %4 = fmul double %3, %3
-; CHECK-NEXT: %5 = fmul double %1, %4
-; CHECK-NEXT: %6 = fmul double %5, %x
-; CHECK-NEXT: %7 = fdiv double 1.000000e+00, %6
+; CHECK-NEXT: %1 = fmul fast double %x, %x
+; CHECK-NEXT: %2 = fmul fast double %1, %1
+; CHECK-NEXT: %3 = fmul fast double %2, %2
+; CHECK-NEXT: %4 = fmul fast double %3, %3
+; CHECK-NEXT: %5 = fmul fast double %1, %4
+; CHECK-NEXT: %6 = fmul fast double %5, %x
+; CHECK-NEXT: %7 = fdiv fast double 1.000000e+00, %6
 ; CHECK-NEXT: ret double %7
   %1 = call fast double @llvm.pow.f64(double %x, double -1.900000e+01)
   ret double %1
@@ -97,11 +97,11 @@ define double @test_simplify_11_23(double %x) {
 define double @test_simplify_32(double %x) {
 ; CHECK-LABEL: @test_simplify_32(
 ; CHECK-NOT: pow
-; CHECK-NEXT: %1 = fmul double %x, %x
-; CHECK-NEXT: %2 = fmul double %1, %1
-; CHECK-NEXT: %3 = fmul double %2, %2
-; CHECK-NEXT: %4 = fmul double %3, %3
-; CHECK-NEXT: %5 = fmul double %4, %4
+; CHECK-NEXT: %1 = fmul fast double %x, %x
+; CHECK-NEXT: %2 = fmul fast double %1, %1
+; CHECK-NEXT: %3 = fmul fast double %2, %2
+; CHECK-NEXT: %4 = fmul fast double %3, %3
+; CHECK-NEXT: %5 = fmul fast double %4, %4
 ; CHECK-NEXT: ret double %5
   %1 = call fast double @llvm.pow.f64(double %x, double 3.200000e+01)
   ret double %1