[InstCombine] canonicalize fdiv after fmul if reassociation is allowed

  (X / Y) * Z --> (X * Z) / Y

This can allow other optimizations/reassociations as shown in the test diffs.

llvm-svn: 358404

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index 7edae55cb3e..a9e3e5f00f6 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -430,6 +430,14 @@ Instruction *InstCombiner::visitFMul(BinaryOperator &I) {
       }
     }
 
+    Value *Z;
+    if (match(&I, m_c_FMul(m_OneUse(m_FDiv(m_Value(X), m_Value(Y))),
+                           m_Value(Z)))) {
+      // Sink division: (X / Y) * Z --> (X * Z) / Y
+      Value *NewFMul = Builder.CreateFMulFMF(X, Z, &I);
+      return BinaryOperator::CreateFDivFMF(NewFMul, Y, &I);
+    }
+
     // sqrt(X) * sqrt(Y) -> sqrt(X * Y)
     // nnan disallows the possibility of returning a number if both operands are
     // negative (in that case, we should return NaN).