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GUFA: Emit RefAsNonNull instead of RefCast where possible #6434

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kripken wants to merge 3 commits into from
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GUFA: Emit RefAsNonNull instead of RefCast where possible #6434

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5285201
fix
kripken Mar 25, 2024
a0f7d5f
fix
kripken Mar 25, 2024
b0857ab
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kripken Mar 25, 2024
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2 changes: 2 additions & 0 deletions scripts/fuzz_opt.py
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Original file line number Diff line number Diff line change
Expand Up @@ -333,6 +333,8 @@ def is_git_repo():
'exception-handling.wast',
'translate-to-new-eh.wast',
'rse-eh.wast',
# The fuzzer does not support non-WTF16 strings.
'gufa-cast-all-strings.wast',
]


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14 changes: 13 additions & 1 deletion src/passes/GUFA.cpp
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Expand Up @@ -385,7 +385,19 @@ struct GUFAOptimizer
auto oracleType = parent.getContents(curr).getType();
if (oracleType.isRef() && oracleType != curr->type &&
Type::isSubType(oracleType, curr->type)) {
replaceCurrent(Builder(*getModule()).makeRefCast(curr, oracleType));
if (oracleType.getHeapType() == curr->type.getHeapType()) {
// These only differ in nullability: use RefAsNonNull. (We do not
// rely on OptimizeInstructions to turn a RefCast into a
// RefAsNonNull, as there are cases where RefCast is actually not
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@tlively tlively Mar 26, 2024

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Suggested change
// RefAsNonNull, as there are cases where RefCast is actually not
// RefAsNonNull, as there are unfortunately cases where RefCast is actually not

// valid, e.g. on a string view, and we want this passes output to
// be valid.)
assert(oracleType.getNullability() == NonNullable);
assert(curr->type.getNullability() == Nullable);
replaceCurrent(Builder(*getModule()).makeRefAs(RefAsNonNull, curr));
} else {
// These differ in the heap type: use RefCast.
replaceCurrent(Builder(*getModule()).makeRefCast(curr, oracleType));
}
optimized = true;
}
}
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90 changes: 90 additions & 0 deletions test/lit/passes/gufa-cast-all-strings.wast
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@@ -0,0 +1,90 @@
;; NOTE: Assertions have been generated by update_lit_checks.py --all-items and should not be edited.

;; RUN: foreach %s %t wasm-opt -all --gufa-cast-all -S -o - | filecheck %s

(module
;; CHECK: (type $0 (func (param stringref stringview_wtf8 stringview_wtf16 stringview_iter)))

;; CHECK: (export "strings-caller" (func $strings-caller))

;; CHECK: (func $strings-target (type $0) (param $a stringref) (param $b stringview_wtf8) (param $c stringview_wtf16) (param $d stringview_iter)
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (ref.as_non_null
;; CHECK-NEXT: (local.get $a)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (ref.as_non_null
;; CHECK-NEXT: (local.get $b)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (ref.as_non_null
;; CHECK-NEXT: (local.get $c)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (ref.as_non_null
;; CHECK-NEXT: (local.get $d)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
(func $strings-target
(param $a (ref null string))
(param $b (ref null stringview_wtf8))
(param $c (ref null stringview_wtf16))
(param $d (ref null stringview_iter))
;; These params are only called with non-null values, so we can cast them
;; to non-null. We must not use ref.cast for that, which is disallowed on
;; strings and views.
(drop
(local.get $a)
)
(drop
(local.get $b)
)
(drop
(local.get $c)
)
(drop
(local.get $d)
)
)

;; CHECK: (func $strings-caller (type $0) (param $a stringref) (param $b stringview_wtf8) (param $c stringview_wtf16) (param $d stringview_iter)
;; CHECK-NEXT: (call $strings-target
;; CHECK-NEXT: (ref.as_non_null
;; CHECK-NEXT: (local.get $a)
;; CHECK-NEXT: )
;; CHECK-NEXT: (ref.as_non_null
;; CHECK-NEXT: (local.get $b)
;; CHECK-NEXT: )
;; CHECK-NEXT: (ref.as_non_null
;; CHECK-NEXT: (local.get $c)
;; CHECK-NEXT: )
;; CHECK-NEXT: (ref.as_non_null
;; CHECK-NEXT: (local.get $d)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
(func $strings-caller (export "strings-caller")
(param $a (ref null string))
(param $b (ref null stringview_wtf8))
(param $c (ref null stringview_wtf16))
(param $d (ref null stringview_iter))
(call $strings-target
(ref.as_non_null
(local.get $a)
)
(ref.as_non_null
(local.get $b)
)
(ref.as_non_null
(local.get $c)
)
(ref.as_non_null
(local.get $d)
)
)
)
)
25 changes: 25 additions & 0 deletions test/lit/passes/gufa-cast-all.wast
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,8 @@

;; CHECK: (export "export1" (func $ref))

;; CHECK: (export "export1.5" (func $ref.null))

;; CHECK: (export "export2" (func $int))

;; CHECK: (export "export3" (func $func))
Expand Down Expand Up @@ -51,6 +53,29 @@
)
)

;; CHECK: (func $ref.null (type $none_=>_none)
;; CHECK-NEXT: (local $a (ref null $A))
;; CHECK-NEXT: (local.set $a
;; CHECK-NEXT: (struct.new_default $A)
;; CHECK-NEXT: )
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (ref.as_non_null
;; CHECK-NEXT: (local.get $a)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
(func $ref.null (export "export1.5")
(local $a (ref null $A))
(local.set $a
(struct.new $A)
)
(drop
;; We can infer that this contains a non-nullable A, and add a cast to
;; non-null on it.
(local.get $a)
)
)

;; CHECK: (func $int (type $none_=>_none)
;; CHECK-NEXT: (local $a i32)
;; CHECK-NEXT: (local.set $a
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