Add a routine to swap branch instruction operands, and update any
profile metadata at the same time. Use it to preserve metadata attached
to a branch when re-writing it in InstCombine.
Add metadata to the canonicalize_branch InstCombine test, and check that
it is tranformed correctly.
Reviewed by Nick Lewycky!
llvm-svn: 142168
diff --git a/llvm/lib/VMCore/Instructions.cpp b/llvm/lib/VMCore/Instructions.cpp
index 82f883a..b3a7205 100644
--- a/llvm/lib/VMCore/Instructions.cpp
+++ b/llvm/lib/VMCore/Instructions.cpp
@@ -785,6 +785,27 @@
SubclassOptionalData = BI.SubclassOptionalData;
}
+void BranchInst::swapSuccessors() {
+ assert(isConditional() &&
+ "Cannot swap successors of an unconditional branch");
+ Op<-1>().swap(Op<-2>());
+
+ // Update profile metadata if present and it matches our structural
+ // expectations.
+ MDNode *ProfileData = getMetadata(LLVMContext::MD_prof);
+ if (!ProfileData || ProfileData->getNumOperands() != 3)
+ return;
+
+ // The first operand is the name. Fetch them backwards and build a new one.
+ Value *Ops[] = {
+ ProfileData->getOperand(0),
+ ProfileData->getOperand(2),
+ ProfileData->getOperand(1)
+ };
+ setMetadata(LLVMContext::MD_prof,
+ MDNode::get(ProfileData->getContext(), Ops));
+}
+
BasicBlock *BranchInst::getSuccessorV(unsigned idx) const {
return getSuccessor(idx);
}