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[Custom Descriptors] OptimizeInstructions: Handle effects in ref.cast_desc when removing ref.as_non_null #8133

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Merged
kripken merged 1 commit into from
Dec 16, 2025
Merged

[Custom Descriptors] OptimizeInstructions: Handle effects in ref.cast_desc when removing ref.as_non_null #8133

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11 changes: 11 additions & 0 deletions src/passes/OptimizeInstructions.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2551,6 +2551,17 @@ struct OptimizeInstructions
// (ref.cast (ref T) ..)
//
if (auto* as = curr->ref->dynCast<RefAs>(); as && as->op == RefAsNonNull) {
if (curr->desc) {
// There is another child here, whose effects we must consider (the same
// ordering situation as in skipNonNullCast: we want to move a trap on
// null past later children).
auto& options = getPassRunner()->options;
EffectAnalyzer descEffects(options, *getModule(), curr->desc);
ShallowEffectAnalyzer movingEffects(options, *getModule(), curr->ref);
if (descEffects.invalidates(movingEffects)) {
return;
}
}
curr->ref = as->value;
curr->type = curr->type.with(NonNullable);
}
Expand Down
113 changes: 96 additions & 17 deletions test/lit/passes/optimize-instructions-desc.wast
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Original file line number Diff line number Diff line change
Expand Up @@ -37,8 +37,8 @@
(type $struct-i32.desc (describes $struct-i32) (struct))
)

;; CHECK: (import "" "" (func $effect (type $6)))
;; NTRAP: (import "" "" (func $effect (type $6)))
;; CHECK: (import "" "" (func $effect (type $4)))
;; NTRAP: (import "" "" (func $effect (type $4)))
(import "" "" (func $effect))

;; CHECK: (func $trap-null-desc (type $10) (result (ref (exact $struct)))
Expand Down Expand Up @@ -128,12 +128,12 @@
)
)

;; CHECK: (func $cast-desc-null-desc (type $6)
;; CHECK: (func $cast-desc-null-desc (type $4)
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (unreachable)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; NTRAP: (func $cast-desc-null-desc (type $6)
;; NTRAP: (func $cast-desc-null-desc (type $4)
;; NTRAP-NEXT: (drop
;; NTRAP-NEXT: (unreachable)
;; NTRAP-NEXT: )
Expand Down Expand Up @@ -375,7 +375,7 @@
)
)

;; CHECK: (func $cast-desc-wrong-desc (type $6)
;; CHECK: (func $cast-desc-wrong-desc (type $4)
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (ref.cast_desc (ref (exact $struct))
;; CHECK-NEXT: (struct.new_default_desc $struct
Expand All @@ -385,7 +385,7 @@
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; NTRAP: (func $cast-desc-wrong-desc (type $6)
;; NTRAP: (func $cast-desc-wrong-desc (type $4)
;; NTRAP-NEXT: (drop
;; NTRAP-NEXT: (block (result (ref (exact $struct)))
;; NTRAP-NEXT: (struct.new_default_desc $struct
Expand All @@ -409,7 +409,7 @@
)
)

;; CHECK: (func $cast-desc-wrong-desc-effects (type $6)
;; CHECK: (func $cast-desc-wrong-desc-effects (type $4)
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (ref.cast_desc (ref (exact $struct))
;; CHECK-NEXT: (block (result (ref (exact $struct)))
Expand All @@ -425,7 +425,7 @@
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; NTRAP: (func $cast-desc-wrong-desc-effects (type $6)
;; NTRAP: (func $cast-desc-wrong-desc-effects (type $4)
;; NTRAP-NEXT: (local $0 (ref (exact $struct)))
;; NTRAP-NEXT: (local $1 (ref (exact $desc)))
;; NTRAP-NEXT: (drop
Expand Down Expand Up @@ -497,9 +497,11 @@
;; CHECK: (func $cast-desc-weaker-nondesc-child-effects (type $14) (param $ref anyref) (param $desc (ref $sub.desc))
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (ref.cast_desc (ref $sub)
;; CHECK-NEXT: (block (result anyref)
;; CHECK-NEXT: (call $effect)
;; CHECK-NEXT: (local.get $ref)
;; CHECK-NEXT: (ref.as_non_null
;; CHECK-NEXT: (block (result anyref)
;; CHECK-NEXT: (call $effect)
;; CHECK-NEXT: (local.get $ref)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: (block (result (ref $sub.desc))
;; CHECK-NEXT: (call $effect)
Expand All @@ -511,9 +513,11 @@
;; NTRAP: (func $cast-desc-weaker-nondesc-child-effects (type $14) (param $ref anyref) (param $desc (ref $sub.desc))
;; NTRAP-NEXT: (drop
;; NTRAP-NEXT: (ref.cast_desc (ref $sub)
;; NTRAP-NEXT: (block (result anyref)
;; NTRAP-NEXT: (call $effect)
;; NTRAP-NEXT: (local.get $ref)
;; NTRAP-NEXT: (ref.as_non_null
;; NTRAP-NEXT: (block (result anyref)
;; NTRAP-NEXT: (call $effect)
;; NTRAP-NEXT: (local.get $ref)
;; NTRAP-NEXT: )
;; NTRAP-NEXT: )
;; NTRAP-NEXT: (block (result (ref $sub.desc))
;; NTRAP-NEXT: (call $effect)
Expand All @@ -524,7 +528,8 @@
;; NTRAP-NEXT: )
(func $cast-desc-weaker-nondesc-child-effects (param $ref anyref) (param $desc (ref $sub.desc))
(drop
;; Same, but with effects.
;; Same, but with effects. Due to ordering, we cannot remove the inner
;; cast (which turns into ref.as_non_null).
(ref.cast_desc (ref $sub)
(ref.cast (ref any)
(block (result anyref)
Expand Down Expand Up @@ -1073,7 +1078,7 @@
)
)

;; CHECK: (func $cast-desc-unreachable-desc (type $6)
;; CHECK: (func $cast-desc-unreachable-desc (type $4)
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (block ;; (replaces unreachable RefCast we can't emit)
;; CHECK-NEXT: (drop
Expand All @@ -1086,7 +1091,7 @@
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; NTRAP: (func $cast-desc-unreachable-desc (type $6)
;; NTRAP: (func $cast-desc-unreachable-desc (type $4)
;; NTRAP-NEXT: (drop
;; NTRAP-NEXT: (block ;; (replaces unreachable RefCast we can't emit)
;; NTRAP-NEXT: (drop
Expand Down Expand Up @@ -1380,4 +1385,78 @@
)
)
)

;; CHECK: (func $ref.cast_desc-ref.as_non_null (type $4)
;; CHECK-NEXT: (local $null (ref null $struct))
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (ref.cast_desc (ref $struct)
;; CHECK-NEXT: (ref.as_non_null
;; CHECK-NEXT: (local.get $null)
;; CHECK-NEXT: )
;; CHECK-NEXT: (block (result (ref null $desc))
;; CHECK-NEXT: (return)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (ref.cast_desc (ref (exact $struct))
;; CHECK-NEXT: (local.get $null)
;; CHECK-NEXT: (struct.new_default $desc)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; NTRAP: (func $ref.cast_desc-ref.as_non_null (type $4)
;; NTRAP-NEXT: (local $null (ref null $struct))
;; NTRAP-NEXT: (local $1 (ref $struct))
;; NTRAP-NEXT: (local $2 (ref null $desc))
;; NTRAP-NEXT: (drop
;; NTRAP-NEXT: (block (result (ref $struct))
;; NTRAP-NEXT: (local.set $1
;; NTRAP-NEXT: (ref.as_non_null
;; NTRAP-NEXT: (local.get $null)
;; NTRAP-NEXT: )
;; NTRAP-NEXT: )
;; NTRAP-NEXT: (local.set $2
;; NTRAP-NEXT: (block (result (ref null $desc))
;; NTRAP-NEXT: (return)
;; NTRAP-NEXT: )
;; NTRAP-NEXT: )
;; NTRAP-NEXT: (local.get $1)
;; NTRAP-NEXT: )
;; NTRAP-NEXT: )
;; NTRAP-NEXT: (drop
;; NTRAP-NEXT: (ref.cast_desc (ref (exact $struct))
;; NTRAP-NEXT: (local.get $null)
;; NTRAP-NEXT: (struct.new_default $desc)
;; NTRAP-NEXT: )
;; NTRAP-NEXT: )
;; NTRAP-NEXT: )
(func $ref.cast_desc-ref.as_non_null
(local $null (ref null $struct))
;; We read a null local and cast it to non-null, trapping. The ref.cast_desc
;; would trap on null anyhow, so it seems we can remove the ref.as_non_null,
;; but doing so would allow us to reach the block, which returns *before* the
;; ref.cast_desc would trap.
(drop
(ref.cast_desc (ref $struct)
(ref.as_non_null
(local.get $null)
)
;; Hide the return in a block, otherwise we'd skip unreachable code.
(block (result (ref null $desc))
(return)
)
)
)
;; As above, but without dangerous effects: we can remove the
;; ref.as_non_null.
(drop
(ref.cast_desc (ref $struct)
(ref.as_non_null
(local.get $null)
)
(struct.new $desc)
)
)
)
)
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