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authorAlon Zakai <azakai@google.com>2021-04-21 12:40:51 -0700
committerGitHub <noreply@github.com>2021-04-21 12:40:51 -0700
commita72f5b7f440a73c23b7f1b0532446584d4da0854 (patch)
tree6043f4c06c2cb358eb940dfbfc614c0f177069d8
parentb4e96d8dd6fded302b7c6be8a34b0a75773737b6 (diff)
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[Wasm GC] Fix handleNonDefaultableLocals on tees (#3830)
When we change a local's type, as we do in that method when we turn a non-nullable (invalid) local into a nullable (valid) one, we must update tees as well as gets - their type must match the changed local type, and we must cast them so that their users do not see a change.
-rw-r--r--src/ir/type-updating.cpp23
-rw-r--r--test/lit/passes/dae-gc.wast49
2 files changed, 71 insertions, 1 deletions
diff --git a/src/ir/type-updating.cpp b/src/ir/type-updating.cpp
index d909bffb4..658fabc83 100644
--- a/src/ir/type-updating.cpp
+++ b/src/ir/type-updating.cpp
@@ -39,6 +39,7 @@ void handleNonDefaultableLocals(Function* func, Module& wasm) {
if (!hasNonNullable) {
return;
}
+
// Rewrite the local.gets.
Builder builder(wasm);
for (auto** getp : FindAllPointers<LocalGet>(func->body).list) {
@@ -56,8 +57,28 @@ void handleNonDefaultableLocals(Function* func, Module& wasm) {
}
}
+ // Update tees, whose type must match the local (if the wasm spec changes for
+ // the type to be that of the value, then this can be removed).
+ for (auto** setp : FindAllPointers<LocalSet>(func->body).list) {
+ auto* set = (*setp)->cast<LocalSet>();
+ if (!func->isVar(set->index)) {
+ // We do not need to process params, which can legally be non-nullable.
+ continue;
+ }
+ // Non-tees do not change, and unreachable tees can be ignored here as their
+ // type is unreachable anyhow.
+ if (!set->isTee() || set->type == Type::unreachable) {
+ continue;
+ }
+ auto type = func->getLocalType(set->index);
+ if (type.isRef() && !type.isNullable()) {
+ set->type = Type(type.getHeapType(), Nullable);
+ *setp = builder.makeRefAs(RefAsNonNull, set);
+ }
+ }
+
// Rewrite the types of the function's vars (which we can do now, after we
- // are done using them to know which local.gets to fix).
+ // are done using them to know which local.gets etc to fix).
for (auto& type : func->vars) {
if (type.isRef() && !type.isNullable()) {
type = Type(type.getHeapType(), Nullable);
diff --git a/test/lit/passes/dae-gc.wast b/test/lit/passes/dae-gc.wast
new file mode 100644
index 000000000..87e480cc8
--- /dev/null
+++ b/test/lit/passes/dae-gc.wast
@@ -0,0 +1,49 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py and should not be edited.
+;; RUN: wasm-opt %s -all --dae -S -o - | filecheck %s
+
+(module
+ ;; CHECK: (func $foo
+ ;; CHECK-NEXT: (call $bar)
+ ;; CHECK-NEXT: )
+ (func $foo
+ (call $bar
+ (i31.new
+ (i32.const 1)
+ )
+ )
+ )
+ ;; CHECK: (func $bar
+ ;; CHECK-NEXT: (local $0 (ref null i31))
+ ;; CHECK-NEXT: (drop
+ ;; CHECK-NEXT: (ref.as_non_null
+ ;; CHECK-NEXT: (local.tee $0
+ ;; CHECK-NEXT: (i31.new
+ ;; CHECK-NEXT: (i32.const 2)
+ ;; CHECK-NEXT: )
+ ;; CHECK-NEXT: )
+ ;; CHECK-NEXT: )
+ ;; CHECK-NEXT: )
+ ;; CHECK-NEXT: (local.tee $0
+ ;; CHECK-NEXT: (unreachable)
+ ;; CHECK-NEXT: )
+ ;; CHECK-NEXT: )
+ (func $bar (param $0 i31ref)
+ (drop
+ ;; after the parameter is removed, we create a nullable local to replace it,
+ ;; and must update the tee's type accordingly to avoid a validation error,
+ ;; and also add a ref.as_non_null so that the outside still receives the
+ ;; same type as before
+ (local.tee $0
+ (i31.new
+ (i32.const 2)
+ )
+ )
+ )
+ ;; test for an unreachable tee, whose type must be unreachable even after
+ ;; the change (the tee would need to be dropped if it were not unreachable,
+ ;; so the correctness in this case is visible in the output)
+ (local.tee $0
+ (unreachable)
+ )
+ )
+)