[InstCombine] Add optimization of redundant insertvalue instructions.
rdar://problem/11861387
llvm-svn: 208214
diff --git a/llvm/lib/Transforms/InstCombine/InstCombine.h b/llvm/lib/Transforms/InstCombine/InstCombine.h
index 88351a0..8a082fe 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombine.h
+++ b/llvm/lib/Transforms/InstCombine/InstCombine.h
@@ -211,6 +211,7 @@
Instruction *visitStoreInst(StoreInst &SI);
Instruction *visitBranchInst(BranchInst &BI);
Instruction *visitSwitchInst(SwitchInst &SI);
+ Instruction *visitInsertValueInst(InsertValueInst &IV);
Instruction *visitInsertElementInst(InsertElementInst &IE);
Instruction *visitExtractElementInst(ExtractElementInst &EI);
Instruction *visitShuffleVectorInst(ShuffleVectorInst &SVI);
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
index aa81e8c..80c20b7 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
@@ -490,6 +490,42 @@
return std::make_pair(V, nullptr);
}
+/// Try to find redundant insertvalue instructions, like the following ones:
+/// %0 = insertvalue { i8, i32 } undef, i8 %x, 0
+/// %1 = insertvalue { i8, i32 } %0, i8 %y, 0
+/// Here the second instruction inserts values at the same indices, as the
+/// first one, making the first one redundant.
+/// It should be transformed to:
+/// %0 = insertvalue { i8, i32 } undef, i8 %y, 0
+Instruction *InstCombiner::visitInsertValueInst(InsertValueInst &I) {
+ bool IsRedundant = false;
+ ArrayRef<unsigned int> FirstIndices = I.getIndices();
+
+ // If there is a chain of insertvalue instructions (each of them except the
+ // last one has only one use and it's another insertvalue insn from this
+ // chain), check if any of the 'children' uses the same indices as the first
+ // instruction. In this case, the first one is redundant.
+ Value *V = &I;
+ unsigned int Depth = 0;
+ while (V->hasOneUse() && Depth < 10) {
+ User *U = V->user_back();
+ InsertValueInst *UserInsInst = dyn_cast<InsertValueInst>(U);
+ if (!UserInsInst || U->getType() != I.getType()) {
+ break;
+ }
+ if (UserInsInst->getIndices() == FirstIndices) {
+ IsRedundant = true;
+ break;
+ }
+ V = UserInsInst;
+ Depth++;
+ }
+
+ if (IsRedundant)
+ return ReplaceInstUsesWith(I, I.getOperand(0));
+ return nullptr;
+}
+
Instruction *InstCombiner::visitInsertElementInst(InsertElementInst &IE) {
Value *VecOp = IE.getOperand(0);
Value *ScalarOp = IE.getOperand(1);