[InstCombine] Y - ~X --> X + Y + 1 fold (PR42457)
Summary:
I *think* we'd want this new variant, because we obviously
have better handling for `add` as compared to `sub`/`not`.
https://rise4fun.com/Alive/WMn
Fixes [[ https://bugs.llvm.org/show_bug.cgi?id=42457 | PR42457 ]]
Reviewers: spatel, nikic, huihuiz, efriedma
Reviewed By: spatel
Subscribers: RKSimon, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D63992
llvm-svn: 365011
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index 0b0cc4b..ba15b02 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1580,6 +1580,12 @@
if (match(Op1, m_OneUse(m_Add(m_Value(X), m_One()))))
return BinaryOperator::CreateAdd(Builder.CreateNot(X), Op0);
+ // Y - ~X --> (X + 1) + Y
+ if (match(Op1, m_OneUse(m_Not(m_Value(X))))) {
+ return BinaryOperator::CreateAdd(
+ Builder.CreateAdd(Op0, ConstantInt::get(I.getType(), 1)), X);
+ }
+
if (Constant *C = dyn_cast<Constant>(Op0)) {
bool IsNegate = match(C, m_ZeroInt());
Value *X;