commit 9b073470334adfedfe265728382c7c5e07af319b
author Sanjay Patel <spatel@rotateright.com> Tue Aug 07 20:32:55 2018 +0000
committer Sanjay Patel <spatel@rotateright.com> Tue Aug 07 20:32:55 2018 +0000
tree d21cfac23e718e35eb5e341d9746a89938abdd37
parent 3e7b9db2d9943eadc953500c995919a8168cd56a

[InstSimplify] fold fsub+fadd with common operand

llvm-svn: 339176

llvm/lib/Analysis/InstructionSimplify.cpp

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 22ced5a..1380543 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4359,6 +4359,14 @@
                        match(Op1, m_FSub(m_AnyZeroFP(), m_Specific(Op0)))))
     return ConstantFP::getNullValue(Op0->getType());
 
+  // (X - Y) + Y --> X
+  // Y + (X - Y) --> X
+  Value *X;
+  if (FMF.noSignedZeros() && FMF.allowReassoc() &&
+      (match(Op0, m_FSub(m_Value(X), m_Specific(Op1))) ||
+       match(Op1, m_FSub(m_Value(X), m_Specific(Op0)))))
+    return X;
+
   return nullptr;
 }