[Instcombine] Combine consecutive identical fences
Differential Revision: https://reviews.llvm.org/D29314
llvm-svn: 293661
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 1974665..56983dc 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -3268,6 +3268,15 @@
return visitCallSite(II);
}
+// Fence instruction simplification
+Instruction *InstCombiner::visitFenceInst(FenceInst &FI) {
+ // Remove identical consecutive fences.
+ if (auto *NFI = dyn_cast<FenceInst>(FI.getNextNode()))
+ if (FI.isIdenticalTo(NFI))
+ return eraseInstFromFunction(FI);
+ return nullptr;
+}
+
// InvokeInst simplification
//
Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
index 9c684f1..9f16a6f 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
+++ b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
@@ -289,6 +289,7 @@
Instruction *visitLoadInst(LoadInst &LI);
Instruction *visitStoreInst(StoreInst &SI);
Instruction *visitBranchInst(BranchInst &BI);
+ Instruction *visitFenceInst(FenceInst &FI);
Instruction *visitSwitchInst(SwitchInst &SI);
Instruction *visitReturnInst(ReturnInst &RI);
Instruction *visitInsertValueInst(InsertValueInst &IV);