Fixes logic and update tests

Author: SahilPatidar

llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp

@@ -2741,6 +2741,22 @@ Instruction *InstCombinerImpl::visitSub(BinaryOperator &I) {
   return TryToNarrowDeduceFlags();
 }
 
+static FastMathFlags getCorrectFMFForFNeg(FastMathFlags F1, FastMathFlags F2) {
+
+  FastMathFlags NF1 = F1 & F2;
+  FastMathFlags NF2 = F1 | F2;
+  if (NF2.noNaNs())
+    return F2;
+
+  if (NF1.any() || (F1.none() && F2.none()))
+    return NF1;
+
+  if (F1.all() || F2.all())
+    return F2;
+
+  return NF1;
+}
+
 /// This eliminates floating-point negation in either 'fneg(X)' or
 /// 'fsub(-0.0, X)' form by combining into a constant operand.
 static Instruction *foldFNegIntoConstant(Instruction &I, const DataLayout &DL) {
@@ -2758,11 +2774,11 @@ static Instruction *foldFNegIntoConstant(Instruction &I, const DataLayout &DL) {
   // -(X * C) --> X * (-C)
   if (match(FNegOp, m_FMul(m_Value(X), m_Constant(C))))
     if (Constant *NegC = ConstantFoldUnaryOpOperand(Instruction::FNeg, C, DL)) {
-      if (match(C, m_AnyZeroFP()) && I.getFastMathFlags().noInfs()) {
-        return BinaryOperator::CreateFMulFMF(
+      FastMathFlags FMF = cast<FPMathOperator>(I.getOperand(0))->getFastMathFlags();
+      if (I.getFastMathFlags().noInfs()) {
+          return BinaryOperator::CreateFMulFMF(
             X, NegC,
-            I.getFastMathFlags() &
-                cast<FPMathOperator>(I.getOperand(0))->getFastMathFlags());
+            getCorrectFMFForFNeg(I.getFastMathFlags(), FMF));
       }
       return BinaryOperator::CreateFMulFMF(X, NegC, &I);
     }

llvm/test/Transforms/InstCombine/fneg.ll

@@ -1150,4 +1150,46 @@ define float @test_fneg_nsz_mul_with_anyzero(float %a) {
   ret float %f2
 }
 
+define float @test_fneg_ninf_mul_nnan_with_const(float %a) {
+; CHECK-LABEL: @test_fneg_ninf_mul_nnan_with_const(
+; CHECK-NEXT:    [[TMP1:%.*]] = fneg float [[A:%.*]]
+; CHECK-NEXT:    [[F2:%.*]] = call float @llvm.copysign.f32(float 0.000000e+00, float [[TMP1]])
+; CHECK-NEXT:    ret float [[F2]]
+;
+  %f1 = fmul nnan float %a, 0.000000
+  %f2 = fneg ninf float %f1
+  ret float %f2
+}
+
+define float @test_fneg_ninf_mul_nsz_with_const(float %a) {
+; CHECK-LABEL: @test_fneg_ninf_mul_nsz_with_const(
+; CHECK-NEXT:    [[F2:%.*]] = fmul float [[A:%.*]], -0.000000e+00
+; CHECK-NEXT:    ret float [[F2]]
+;
+  %f1 = fmul nsz float %a, 0.000000
+  %f2 = fneg ninf float %f1
+  ret float %f2
+}
+
+define <2 x float> @test_fneg_ninf_mul_nnan_with_vec_const(<2 x float> %a) {
+; CHECK-LABEL: @test_fneg_ninf_mul_nnan_with_vec_const(
+; 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 nnan <2 x float> %a, <float 0.000000, float -0.000000>
+  %f2 = fneg ninf <2 x float> %f1
+  ret <2 x float> %f2
+}
+
+define <2 x float> @test_fneg_ninf_mul_nsz_with_vec_const(<2 x float> %a) {
+; CHECK-LABEL: @test_fneg_ninf_mul_nsz_with_vec_const(
+; CHECK-NEXT:    [[F2:%.*]] = fmul <2 x float> [[A:%.*]], <float -0.000000e+00, float 0.000000e+00>
+; CHECK-NEXT:    ret <2 x float> [[F2]]
+;
+  %f1 = fmul nsz <2 x float> %a, <float 0.000000, float -0.000000>
+  %f2 = fneg ninf <2 x float> %f1
+  ret <2 x float> %f2
+}
+
+
 !0 = !{}