================
@@ -20,17 +21,117 @@ using namespace cir;
// Helpers
//===----------------------------------------------------------------------===//
+static constexpr unsigned MaxLookupDepth = 6;
+
mlir::Value CIRBasicAliasAnalysis::getUnderlyingObject(mlir::Value val) {
LDBG() << "Getting underlying object for: " << val;
- // TODO: Walk through cir.ptr_stride, cir.cast, cir.get_member, etc.
- // to find the root allocation (cir.alloca, cir.global_addr, function args).
- LDBG() << "Not yet implemented";
+ for (unsigned depth = 0; depth < MaxLookupDepth; ++depth) {
+ mlir::Operation *defOp = val.getDefiningOp();
+ if (!defOp) {
+ LDBG() << "No defining operation, stopping";
+ break; // Block argument (e.g. function parameter) — stop here.
+ }
+
+ // Bitcast and address-space casts don't change the underlying object.
+ // array_to_ptrdecay produces an element pointer to the same storage as
+ // the array pointer, so strip through it too.
+ if (auto castOp = mlir::dyn_cast<cir::CastOp>(defOp)) {
+ if (castOp.isAllocaPreservingCast() ||
+ castOp.getKind() == cir::CastKind::array_to_ptrdecay) {
----------------
bcardosolopes wrote:
IIUC, your note on `isAllocaPreservingCast` says the opposite (CIROps.td:335):
decay "changes the scope of the memory object, so we exclude it here".
Stripping it here is what gets you `arr#0 <-> ptr#0: MustAlias`, whole array
against first element.
Which one is right? If the strip is fine for AA the note wants updating, and
this probably belongs behind a second predicate on `CastOp` rather than an `||`
at the use site.
https://github.com/llvm/llvm-project/pull/215683
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