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MergeBlocks: Migrate from invalidates to orderedBefore #8767

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Merged
tlively merged 3 commits into from
May 26, 2026
+86 −21
Merged

MergeBlocks: Migrate from invalidates to orderedBefore #8767

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70191cf
MergeBlocks: Migrate from invalidates to orderedBefore
tlively May 21, 2026
ab52b47
Merge branch 'main' into merge-blocks-ordered-effects
tlively May 24, 2026
51a5986
update comments
tlively May 26, 2026
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24 changes: 3 additions & 21 deletions src/passes/MergeBlocks.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -498,29 +498,11 @@ struct MergeBlocks
// )
// at which point the block is on the outside and potentially mergeable with
// an outer block
Block* optimize(Expression* curr,
Expression*& child,
Block* outer = nullptr,
Expression** dependency1 = nullptr,
Expression** dependency2 = nullptr) {
Block*
optimize(Expression* curr, Expression*& child, Block* outer = nullptr) {
if (!child) {
return outer;
}
if ((dependency1 && *dependency1) || (dependency2 && *dependency2)) {
// there are dependencies, things we must be reordered through. make sure
// no problems there
EffectAnalyzer childEffects(getPassOptions(), *getModule(), child);
if (dependency1 && *dependency1 &&
EffectAnalyzer(getPassOptions(), *getModule(), *dependency1)
.invalidates(childEffects)) {
return outer;
}
if (dependency2 && *dependency2 &&
EffectAnalyzer(getPassOptions(), *getModule(), *dependency2)
.invalidates(childEffects)) {
return outer;
}
}
if (auto* block = child->dynCast<Block>()) {
if (!block->name.is() && block->list.size() >= 2) {
auto* back = block->list.back();
Expand Down Expand Up @@ -665,7 +647,7 @@ struct MergeBlocks
EffectAnalyzer blockChildEffects(
getPassOptions(), *getModule(), blockChild);
for (auto& effects : childEffects) {
if (blockChildEffects.invalidates(effects)) {
if (effects.orderedBefore(blockChildEffects)) {
fail = true;
break;
}
Expand Down
83 changes: 83 additions & 0 deletions test/lit/passes/merge-blocks-atomics.wast
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@@ -0,0 +1,83 @@
;; NOTE: Assertions have been generated by update_lit_checks.py and should not be edited.
;; RUN: wasm-opt %s --merge-blocks -all -S -o - | filecheck %s

(module
;; CHECK: (type $struct (shared (struct (field (mut i32)))))
(type $struct (shared (struct (field (mut i32)))))

;; CHECK: (memory $mem 1 1 shared)
(memory $mem 1 1 shared)

;; CHECK: (func $foo (type $2) (param $0 i32) (param $1 i32)
;; CHECK-NEXT: )
(func $foo (param i32 i32))

;; CHECK: (func $disallowed (type $1) (param $x (ref $struct))
;; CHECK-NEXT: (call $foo
;; CHECK-NEXT: (block $label1 (result i32)
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (i32.atomic.load acqrel
;; CHECK-NEXT: (i32.const 0)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: (i32.const 0)
;; CHECK-NEXT: )
;; CHECK-NEXT: (block (result i32)
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (struct.get $struct 0
;; CHECK-NEXT: (local.get $x)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: (i32.const 0)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
(func $disallowed (param $x (ref $struct))
;; Test 1: Disallowed reordering (GC read NOT moved before acquire load).
(call $foo
;; This block is left behind because it is named.
(block $block (result i32)
(drop (i32.atomic.load acqrel (i32.const 0)))
(i32.const 0)
)
;; This block tries to move back past $block and out of $foo, but cannot.
(block (result i32)
(drop (struct.get $struct 0 (local.get $x)))
(i32.const 0)
)
)
)

;; CHECK: (func $allowed (type $1) (param $x (ref $struct))
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (struct.get $struct 0
;; CHECK-NEXT: (local.get $x)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: (call $foo
;; CHECK-NEXT: (block $label2 (result i32)
;; CHECK-NEXT: (i32.atomic.store acqrel
;; CHECK-NEXT: (i32.const 0)
;; CHECK-NEXT: (i32.const 42)
;; CHECK-NEXT: )
;; CHECK-NEXT: (i32.const 0)
;; CHECK-NEXT: )
;; CHECK-NEXT: (i32.const 0)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
(func $allowed (param $x (ref $struct))
;; Test 2: Allowed reordering (GC read moved before Wasm release store)
(call $foo
;; This block is left behind because it is named.
(block $block (result i32)
(i32.atomic.store acqrel (i32.const 0) (i32.const 42))
(i32.const 0)
)
;; This block can move back past $block and out of $foo.
(block (result i32)
(drop (struct.get $struct 0 (local.get $x)))
(i32.const 0)
)
)
)
)
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