Update Flag Propagation Logic

Author: SahilPatidar

llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp

@@ -2757,8 +2757,12 @@ static Instruction *foldFNegIntoConstant(Instruction &I, const DataLayout &DL) {
   // Fold negation into constant operand.
   // -(X * C) --> X * (-C)
   if (match(FNegOp, m_FMul(m_Value(X), m_Constant(C))))
-    if (Constant *NegC = ConstantFoldUnaryOpOperand(Instruction::FNeg, C, DL))
-      return BinaryOperator::CreateFMulFMF(X, NegC, FNegOp);
+    if (Constant *NegC = ConstantFoldUnaryOpOperand(Instruction::FNeg, C, DL)) {
+      FastMathFlags Flag = I.getFastMathFlags() | FNegOp->getFastMathFlags();
+      Flag.setNoInfs(I.getFastMathFlags().noInfs() &&
+                     FNegOp->getFastMathFlags().noInfs());
+      return BinaryOperator::CreateFMulFMF(X, NegC, Flag);
+    }
   // -(X / C) --> X / (-C)
   if (match(FNegOp, m_FDiv(m_Value(X), m_Constant(C))))
     if (Constant *NegC = ConstantFoldUnaryOpOperand(Instruction::FNeg, C, DL))

llvm/test/Transforms/InstCombine/fneg.ll

@@ -41,7 +41,7 @@ define float @fmul_fneg(float %x) {
 
 define float @fmul_fsub_fmf(float %x) {
 ; CHECK-LABEL: @fmul_fsub_fmf(
-; CHECK-NEXT:    [[R:%.*]] = fmul float [[X:%.*]], -4.200000e+01
+; CHECK-NEXT:    [[R:%.*]] = fmul reassoc nsz float [[X:%.*]], -4.200000e+01
 ; CHECK-NEXT:    ret float [[R]]
 ;
   %m = fmul float %x, 42.0
@@ -51,7 +51,7 @@ define float @fmul_fsub_fmf(float %x) {
 
 define float @fmul_fneg_fmf(float %x) {
 ; CHECK-LABEL: @fmul_fneg_fmf(
-; CHECK-NEXT:    [[R:%.*]] = fmul float [[X:%.*]], -4.200000e+01
+; CHECK-NEXT:    [[R:%.*]] = fmul reassoc nsz float [[X:%.*]], -4.200000e+01
 ; CHECK-NEXT:    ret float [[R]]
 ;
   %m = fmul float %x, 42.0
@@ -1131,7 +1131,8 @@ define float @test_fsub_ninf_mul_with_anyzero(float %a) {
 
 define float @test_fneg_nnan_mul_with_anyzero(float %a) {
 ; CHECK-LABEL: @test_fneg_nnan_mul_with_anyzero(
-; CHECK-NEXT:    [[F2:%.*]] = fmul ninf float [[A:%.*]], -0.000000e+00
+; CHECK-NEXT:    [[TMP1:%.*]] = fneg nnan float [[A:%.*]]
+; CHECK-NEXT:    [[F2:%.*]] = call nnan float @llvm.copysign.f32(float 0.000000e+00, float [[TMP1]])
 ; CHECK-NEXT:    ret float [[F2]]
 ;
   %f1 = fmul ninf float %a, 0.000000
@@ -1141,7 +1142,7 @@ define float @test_fneg_nnan_mul_with_anyzero(float %a) {
 
 define float @test_fneg_nsz_mul_with_anyzero(float %a) {
 ; CHECK-LABEL: @test_fneg_nsz_mul_with_anyzero(
-; CHECK-NEXT:    [[F2:%.*]] = fmul ninf float [[A:%.*]], -0.000000e+00
+; CHECK-NEXT:    [[F2:%.*]] = fmul nsz float [[A:%.*]], -0.000000e+00
 ; CHECK-NEXT:    ret float [[F2]]
 ;
   %f1 = fmul ninf float %a, 0.000000
@@ -1192,7 +1193,7 @@ define <2 x float> @test_fneg_ninf_mul_nsz_with_vec_const(<2 x float> %a) {
 
 define <2 x float> @test_fneg_nnan_ninf_mul_with_vec_const(<2 x float> %a) {
 ; CHECK-LABEL: @test_fneg_nnan_ninf_mul_with_vec_const(
-; CHECK-NEXT:    [[F2:%.*]] = fmul <2 x float> [[A:%.*]], <float -0.000000e+00, float 0.000000e+00>
+; CHECK-NEXT:    [[F2:%.*]] = fmul nnan <2 x float> [[A:%.*]], <float -0.000000e+00, float 0.000000e+00>
 ; CHECK-NEXT:    ret <2 x float> [[F2]]
 ;
   %f1 = fmul <2 x float> %a, <float 0.000000, float -0.000000>

llvm/test/Transforms/InstCombine/fsub.ll

@@ -98,7 +98,7 @@ define float @sub_sub_nsz(float %x, float %y, float %z) {
 
 define float @sub_add_neg_x(float %x, float %y) {
 ; CHECK-LABEL: @sub_add_neg_x(
-; CHECK-NEXT:    [[R:%.*]] = fmul float [[X:%.*]], -5.000000e+00
+; CHECK-NEXT:    [[R:%.*]] = fmul reassoc nsz float [[X:%.*]], -5.000000e+00
 ; CHECK-NEXT:    ret float [[R]]
 ;
   %mul = fmul float %x, 5.000000e+00