Optimize x86-64 addressing with a 32-bit unsigned index.
Change-Id: I65aff3da87dfb9c3e5db58621a1a02944a6065e8
Reviewed-on: https://chromium-review.googlesource.com/433365
Reviewed-by: Jim Stichnoth <stichnot@chromium.org>
diff --git a/src/IceTargetLoweringX86BaseImpl.h b/src/IceTargetLoweringX86BaseImpl.h
index 6abb340..65041e8 100644
--- a/src/IceTargetLoweringX86BaseImpl.h
+++ b/src/IceTargetLoweringX86BaseImpl.h
@@ -5497,6 +5497,22 @@
if (IndexInst == nullptr)
return nullptr;
assert(!VMetadata->isMultiDef(*Index));
+
+ // When using an unsigned 32-bit array index on x64, it gets zero-extended
+ // before the shift & add. The explicit zero extension can be eliminated
+ // because x86 32-bit operations automatically get zero-extended into the
+ // corresponding 64-bit register.
+ if (auto *CastInst = llvm::dyn_cast<InstCast>(IndexInst)) {
+ if (CastInst->getCastKind() == InstCast::Zext) {
+ if (auto *Var = llvm::dyn_cast<Variable>(CastInst->getSrc(0))) {
+ if (Var->getType() == IceType_i32 &&
+ CastInst->getDest()->getType() == IceType_i64) {
+ IndexInst = VMetadata->getSingleDefinition(Var);
+ }
+ }
+ }
+ }
+
if (IndexInst->getSrcSize() < 2)
return nullptr;
if (auto *ArithInst = llvm::dyn_cast<InstArithmetic>(IndexInst)) {
