[GCRelocate] Add a peephole to canonicalize base pointer relocation
If we generate the gc.relocate, and then later prove two arguments to the statepoint are equivalent, we should canonicalize the gc.relocate to the form we would have produced if this had been known before rewriting.
llvm-svn: 372771
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 0b4e9e9..5c0e648 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -3951,10 +3951,21 @@
break;
}
case Intrinsic::experimental_gc_relocate: {
+ auto &GCR = *cast<GCRelocateInst>(II);
+
+ // If we have two copies of the same pointer in the statepoint argument
+ // list, canonicalize to one. This may let us common gc.relocates.
+ if (GCR.getBasePtr() == GCR.getDerivedPtr() &&
+ GCR.getBasePtrIndex() != GCR.getDerivedPtrIndex()) {
+ auto *OpIntTy = GCR.getOperand(2)->getType();
+ II->setOperand(2, ConstantInt::get(OpIntTy, GCR.getBasePtrIndex()));
+ return II;
+ }
+
// Translate facts known about a pointer before relocating into
// facts about the relocate value, while being careful to
// preserve relocation semantics.
- Value *DerivedPtr = cast<GCRelocateInst>(II)->getDerivedPtr();
+ Value *DerivedPtr = GCR.getDerivedPtr();
// Remove the relocation if unused, note that this check is required
// to prevent the cases below from looping forever.