Revert [InstCombine] Use SimplifyFMulInst to simplify multiply in fma.

This introduces additional rounding error in some cases. See D67434.

This reverts r371518 (git commit 18a1f08)

llvm-svn: 371634

Author: fhahn

llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp

@@ -2258,11 +2258,9 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
       return II;
     }
 
-    // Try to simplify the underlying FMul.
-    if (Value *V = SimplifyFMulInst(II->getArgOperand(0), II->getArgOperand(1),
-                                    II->getFastMathFlags(),
-                                    SQ.getWithInstruction(II))) {
-      auto *FAdd = BinaryOperator::CreateFAdd(V, II->getArgOperand(2));
+    // fma x, 1, z -> fadd x, z
+    if (match(Src1, m_FPOne())) {
+      auto *FAdd = BinaryOperator::CreateFAdd(Src0, II->getArgOperand(2));
       FAdd->copyFastMathFlags(II);
       return FAdd;
     }

llvm/test/Transforms/InstCombine/fma.ll

@@ -372,7 +372,8 @@ define float @fmuladd_x_1_z_fast(float %x, float %z) {
 define <2 x double> @fmuladd_a_0_b(<2 x double> %a, <2 x double> %b) {
 ; CHECK-LABEL: @fmuladd_a_0_b(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    ret <2 x double> [[B:%.*]]
+; CHECK-NEXT:    [[RES:%.*]] = call nnan nsz <2 x double> @llvm.fmuladd.v2f64(<2 x double> [[A:%.*]], <2 x double> zeroinitializer, <2 x double> [[B:%.*]])
+; CHECK-NEXT:    ret <2 x double> [[RES]]
 ;
 entry:
   %res = call nnan nsz <2 x double> @llvm.fmuladd.v2f64(<2 x double> %a, <2 x double> zeroinitializer, <2 x double> %b)
@@ -382,7 +383,8 @@ entry:
 define <2 x double> @fmuladd_0_a_b(<2 x double> %a, <2 x double> %b) {
 ; CHECK-LABEL: @fmuladd_0_a_b(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    ret <2 x double> [[B:%.*]]
+; CHECK-NEXT:    [[RES:%.*]] = call nnan nsz <2 x double> @llvm.fmuladd.v2f64(<2 x double> [[A:%.*]], <2 x double> zeroinitializer, <2 x double> [[B:%.*]])
+; CHECK-NEXT:    ret <2 x double> [[RES]]
 ;
 entry:
   %res = call nnan nsz <2 x double> @llvm.fmuladd.v2f64(<2 x double> zeroinitializer, <2 x double> %a, <2 x double> %b)
@@ -405,7 +407,8 @@ declare <2 x double> @llvm.fmuladd.v2f64(<2 x double>, <2 x double>, <2 x double
 define <2 x double> @fma_a_0_b(<2 x double> %a, <2 x double> %b) {
 ; CHECK-LABEL: @fma_a_0_b(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    ret <2 x double> [[B:%.*]]
+; CHECK-NEXT:    [[RES:%.*]] = call nnan nsz <2 x double> @llvm.fma.v2f64(<2 x double> [[A:%.*]], <2 x double> zeroinitializer, <2 x double> [[B:%.*]])
+; CHECK-NEXT:    ret <2 x double> [[RES]]
 ;
 entry:
   %res = call nnan nsz <2 x double> @llvm.fma.v2f64(<2 x double> %a, <2 x double> zeroinitializer, <2 x double> %b)
@@ -415,7 +418,8 @@ entry:
 define <2 x double> @fma_0_a_b(<2 x double> %a, <2 x double> %b) {
 ; CHECK-LABEL: @fma_0_a_b(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    ret <2 x double> [[B:%.*]]
+; CHECK-NEXT:    [[RES:%.*]] = call nnan nsz <2 x double> @llvm.fma.v2f64(<2 x double> [[A:%.*]], <2 x double> zeroinitializer, <2 x double> [[B:%.*]])
+; CHECK-NEXT:    ret <2 x double> [[RES]]
 ;
 entry:
   %res = call nnan nsz <2 x double> @llvm.fma.v2f64(<2 x double> zeroinitializer, <2 x double> %a, <2 x double> %b)
@@ -436,7 +440,8 @@ entry:
 define <2 x double> @fma_sqrt(<2 x double> %a, <2 x double> %b) {
 ; CHECK-LABEL: @fma_sqrt(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[RES:%.*]] = fadd fast <2 x double> [[A:%.*]], [[B:%.*]]
+; CHECK-NEXT:    [[SQRT:%.*]] = call fast <2 x double> @llvm.sqrt.v2f64(<2 x double> [[A:%.*]])
+; CHECK-NEXT:    [[RES:%.*]] = call fast <2 x double> @llvm.fma.v2f64(<2 x double> [[SQRT]], <2 x double> [[SQRT]], <2 x double> [[B:%.*]])
 ; CHECK-NEXT:    ret <2 x double> [[RES]]
 ;
 entry: