[PATCH] D43398: [InstCombine] allow fdiv folds with less than fully 'fast' ops

[Sanjay Patel via Phabricator via llvm-commits]

spatel updated this revision to Diff 135446.
spatel added a comment.

Patch updated:
Propagate FMF from the last fdiv to the new fmul.


https://reviews.llvm.org/D43398

Files:
  lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
  test/Transforms/InstCombine/fdiv.ll


Index: test/Transforms/InstCombine/fdiv.ll
===================================================================
--- test/Transforms/InstCombine/fdiv.ll
+++ test/Transforms/InstCombine/fdiv.ll
@@ -126,25 +126,25 @@
 
 define float @div_with_div_numerator(float %x, float %y, float %z) {
 ; CHECK-LABEL: @div_with_div_numerator(
-; CHECK-NEXT:    [[TMP1:%.*]] = fmul ninf float [[Y:%.*]], [[Z:%.*]]
-; CHECK-NEXT:    [[DIV2:%.*]] = fdiv fast float [[X:%.*]], [[TMP1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = fmul reassoc arcp float [[Y:%.*]], [[Z:%.*]]
+; CHECK-NEXT:    [[DIV2:%.*]] = fdiv reassoc arcp float [[X:%.*]], [[TMP1]]
 ; CHECK-NEXT:    ret float [[DIV2]]
 ;
   %div1 = fdiv ninf float %x, %y
-  %div2 = fdiv fast float %div1, %z
+  %div2 = fdiv arcp reassoc float %div1, %z
   ret float %div2
 }
 
 ; Z / (X / Y) --> (Z * Y) / X
 
 define <2 x float> @div_with_div_denominator(<2 x float> %x, <2 x float> %y, <2 x float> %z) {
 ; CHECK-LABEL: @div_with_div_denominator(
-; CHECK-NEXT:    [[TMP1:%.*]] = fmul nnan <2 x float> [[Y:%.*]], [[Z:%.*]]
-; CHECK-NEXT:    [[DIV2:%.*]] = fdiv fast <2 x float> [[TMP1]], [[X:%.*]]
+; CHECK-NEXT:    [[TMP1:%.*]] = fmul reassoc arcp <2 x float> [[Y:%.*]], [[Z:%.*]]
+; CHECK-NEXT:    [[DIV2:%.*]] = fdiv reassoc arcp <2 x float> [[TMP1]], [[X:%.*]]
 ; CHECK-NEXT:    ret <2 x float> [[DIV2]]
 ;
   %div1 = fdiv nnan <2 x float> %x, %y
-  %div2 = fdiv fast <2 x float> %z, %div1
+  %div2 = fdiv arcp reassoc <2 x float> %z, %div1
   ret <2 x float> %div2
 }
 
@@ -342,8 +342,8 @@
 
 define <2 x float> @div_constant_dividend3(<2 x float> %x) {
 ; CHECK-LABEL: @div_constant_dividend3(
-; CHECK-NEXT:    [[T1:%.*]] = fdiv <2 x float> <float 3.000000e+00, float 7.000000e+00>, [[X:%.*]]
-; CHECK-NEXT:    [[T2:%.*]] = fdiv reassoc arcp <2 x float> <float 1.500000e+01, float -7.000000e+00>, [[T1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = fmul reassoc arcp <2 x float> [[X:%.*]], <float 1.500000e+01, float -7.000000e+00>
+; CHECK-NEXT:    [[T2:%.*]] = fmul reassoc arcp <2 x float> [[TMP1]], <float 0x3FD5555560000000, float 0x3FC24924A0000000>
 ; CHECK-NEXT:    ret <2 x float> [[T2]]
 ;
   %t1 = fdiv <2 x float> <float 3.0e0, float 7.0e0>, %x
Index: lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -1373,28 +1373,18 @@
       if (Instruction *R = FoldOpIntoSelect(I, SI))
         return R;
 
-  if (I.isFast()) {
+  if (I.hasAllowReassoc() && I.hasAllowReciprocal()) {
     Value *X, *Y;
     if (match(Op0, m_OneUse(m_FDiv(m_Value(X), m_Value(Y)))) &&
         (!isa<Constant>(Y) || !isa<Constant>(Op1))) {
       // (X / Y) / Z => X / (Y * Z)
-      Value *YZ = Builder.CreateFMul(Y, Op1);
-      if (auto *YZInst = dyn_cast<Instruction>(YZ)) {
-        FastMathFlags FMFIntersect = I.getFastMathFlags();
-        FMFIntersect &= cast<Instruction>(Op0)->getFastMathFlags();
-        YZInst->setFastMathFlags(FMFIntersect);
-      }
+      Value *YZ = Builder.CreateFMulFMF(Y, Op1, &I);
       return BinaryOperator::CreateFDivFMF(X, YZ, &I);
     }
     if (match(Op1, m_OneUse(m_FDiv(m_Value(X), m_Value(Y)))) &&
         (!isa<Constant>(Y) || !isa<Constant>(Op0))) {
       // Z / (X / Y) => (Y * Z) / X
-      Value *YZ = Builder.CreateFMul(Y, Op0);
-      if (auto *YZInst = dyn_cast<Instruction>(YZ)) {
-        FastMathFlags FMFIntersect = I.getFastMathFlags();
-        FMFIntersect &= cast<Instruction>(Op1)->getFastMathFlags();
-        YZInst->setFastMathFlags(FMFIntersect);
-      }
+      Value *YZ = Builder.CreateFMulFMF(Y, Op0, &I);
       return BinaryOperator::CreateFDivFMF(YZ, X, &I);
     }
   }


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