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Precompute: Ignore mutable arrays in StringNew #6522

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Merged
kripken merged 3 commits into from
Apr 23, 2024
Merged

Precompute: Ignore mutable arrays in StringNew #6522

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kripken Apr 22, 2024
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kripken Apr 22, 2024
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kripken Apr 22, 2024
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22 changes: 22 additions & 0 deletions src/passes/Precompute.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -195,6 +195,28 @@ class PrecomputingExpressionRunner
return Literal(canonical, curr->type.getHeapType());
}

Flow visitStringNew(StringNew* curr) {
if (curr->op != StringNewWTF16Array) {
// TODO: handle other string ops. For now we focus on JS-like strings.
return Flow(NONCONSTANT_FLOW);
}

// string.encode_wtf16_array is effectively an Array read operation, so
// just like ArrayGet above we must check for immutability.
auto ptrType = curr->ptr->type;
if (ptrType.isRef()) {
auto heapType = ptrType.getHeapType();
if (heapType.isArray()) {
if (heapType.getArray().element.mutable_ == Immutable) {
return Super::visitStringNew(curr);
}
}
}

// Otherwise, this is mutable or unreachable or otherwise uninteresting.
return Flow(NONCONSTANT_FLOW);
}

Flow visitStringEncode(StringEncode* curr) {
// string.encode_wtf16_array is effectively an Array write operation, so
// just like ArraySet and ArrayCopy above we must mark it as disallowed
Expand Down
52 changes: 50 additions & 2 deletions test/lit/passes/precompute-strings.wast
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Expand Up @@ -8,9 +8,13 @@
;; CHECK: (type $array16 (array (mut i16)))
(type $array16 (array (mut i16)))

(type $array16-imm (array i16))

;; CHECK: (type $2 (func (result (ref string))))

;; CHECK: (type $3 (func (result (ref any))))
;; CHECK: (type $3 (func (result anyref)))

;; CHECK: (type $4 (func (result (ref any))))

;; CHECK: (export "get_codepoint-unicode" (func $get_codepoint-unicode))

Expand Down Expand Up @@ -169,7 +173,7 @@
)
)

;; CHECK: (func $encode-stashed (type $3) (result (ref any))
;; CHECK: (func $encode-stashed (type $4) (result (ref any))
;; CHECK-NEXT: (local $1 (ref $array16))
;; CHECK-NEXT: (local.set $1
;; CHECK-NEXT: (array.new_default $array16
Expand Down Expand Up @@ -234,4 +238,48 @@
(i32.const 6)
)
)

;; CHECK: (func $string.new-mutable (type $3) (result anyref)
;; CHECK-NEXT: (string.new_wtf16_array
;; CHECK-NEXT: (array.new_fixed $array16 4
;; CHECK-NEXT: (i32.const 65)
;; CHECK-NEXT: (i32.const 66)
;; CHECK-NEXT: (i32.const 67)
;; CHECK-NEXT: (i32.const 68)
;; CHECK-NEXT: )
;; CHECK-NEXT: (i32.const 0)
;; CHECK-NEXT: (i32.const 4)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
(func $string.new-mutable (result anyref)
;; We do not precompute this because the array is mutable, and we do not yet
;; do an analysis to see that it does not "escape" into places that modify it.
(string.new_wtf16_array
(array.new_fixed $array16 4
(i32.const 65)
(i32.const 66)
(i32.const 67)
(i32.const 68)
)
(i32.const 0)
(i32.const 4)
)
)

;; CHECK: (func $string.new-immutable (type $3) (result anyref)
;; CHECK-NEXT: (string.const "ABCD")
;; CHECK-NEXT: )
(func $string.new-immutable (result anyref)
;; This array is immutable and we can optimize here.
(string.new_wtf16_array
(array.new_fixed $array16-imm 4
(i32.const 65)
(i32.const 66)
(i32.const 67)
(i32.const 68)
)
(i32.const 0)
(i32.const 4)
)
)
)