[PATCH] D129844: [InstCombine] Restrict "(X & 0xFF00) + xx00 --> (X + xx00) & 0xFF00"

[Piotr Sobczak via Phabricator via llvm-commits]

piotr updated this revision to Diff 444945.
piotr added a comment.

Rebased on top of 2d9332646a9c <https://reviews.llvm.org/rG2d9332646a9c37eb2934a4370a57ead2aece706f>.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D129844/new/

https://reviews.llvm.org/D129844

Files:
  llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
  llvm/test/Transforms/InstCombine/add.ll


Index: llvm/test/Transforms/InstCombine/add.ll
===================================================================
--- llvm/test/Transforms/InstCombine/add.ll
+++ llvm/test/Transforms/InstCombine/add.ll
@@ -761,8 +761,8 @@
 
 define i8 @masked_add_multi_use(i8 %x) {
 ; CHECK-LABEL: @masked_add_multi_use(
-; CHECK-NEXT:    [[TMP:%.*]] = add i8 [[X:%.*]], 96
-; CHECK-NEXT:    [[R:%.*]] = and i8 [[TMP:%.*]], -16
+; CHECK-NEXT:    [[AND:%.*]] = and i8 [[X:%.*]], -16
+; CHECK-NEXT:    [[R:%.*]] = add i8 [[AND]], 96
 ; CHECK-NEXT:    call void @use(i8 [[X]])
 ; CHECK-NEXT:    ret i8 [[R]]
 ;
Index: llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -972,7 +972,7 @@
   // If all bits affected by the add are included in a high-bit-mask, do the
   // add before the mask op:
   // (X & 0xFF00) + xx00 --> (X + xx00) & 0xFF00
-  if (match(Op0, m_OneUse(m_And(m_Value(X), m_APInt(C2)))) &&
+  if (match(Op0, m_OneUse(m_And(m_OneUse(m_Value(X)), m_APInt(C2)))) &&
       C2->isNegative() && C2->isShiftedMask() && *C == (*C & *C2)) {
     Value *NewAdd = Builder.CreateAdd(X, ConstantInt::get(Ty, *C));
     return BinaryOperator::CreateAnd(NewAdd, ConstantInt::get(Ty, *C2));


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