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Merged
kripken merged 9 commits into from
Feb 8, 2024
Merged

Add a pass to propagate global constants to other globals #6287

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kripken Feb 7, 2024
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Merge remote-tracking branch 'origin/main' into prop.glob
kripken Feb 8, 2024
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test
kripken Feb 8, 2024
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Merge remote-tracking branch 'origin/main' into prop.glob
kripken Feb 8, 2024
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test
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@kripken
kripken committed Feb 8, 2024
commit eb9128a5197d0c32473bff81e47c2c09a3781c02
5 changes: 3 additions & 2 deletions src/passes/SimplifyGlobals.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -673,11 +673,12 @@ struct SimplifyGlobals : public Pass {
// go, as well as applying them where possible.
for (auto& global : module->globals) {
if (!global->imported()) {
// Apply globals to this value, which may turn it into a constant we can
// further propagate, or it may already have been one.
applyGlobals(global->init);
Comment on lines +676 to +678
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@tlively tlively Feb 8, 2024

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This looks like a bug fix. Which test case does it affect?

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@kripken kripken Feb 8, 2024

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It's not a bugfix, see the second paragraph above: This makes us slightly more efficient in SimplifyGlobals, but we always did it.

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@kripken kripken Feb 8, 2024

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Testcase: https://github.com/WebAssembly/binaryen/pull/6287/files#diff-b20b12708a3cf7de01646f83ed600c7dc546c88505309a98ecb19e1b3f9eda65R35

if (Properties::isConstantExpression(global->init)) {
constantGlobals[global->name] =
getLiteralsFromConstExpression(global->init);
} else {
applyGlobals(global->init);
}
}
}
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23 changes: 18 additions & 5 deletions test/lit/passes/propagate-globals-globally.wast
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Expand Up @@ -6,7 +6,10 @@
;; The global constants should be applied to other globals.

(module
;; CHECK: (type $0 (func))
;; CHECK: (type $struct (struct (field stringref) (field stringref)))
(type $struct (struct stringref stringref))

;; CHECK: (type $1 (func))

;; CHECK: (global $A i32 (i32.const 42))
(global $A i32 (i32.const 42))
Expand All @@ -15,21 +18,31 @@
(global $B i32 (global.get $A))

;; CHECK: (global $C i32 (i32.add
;; CHECK-NEXT: (global.get $B)
;; CHECK-NEXT: (i32.const 42)
;; CHECK-NEXT: (i32.const 42)
;; CHECK-NEXT: ))
(global $C i32 (i32.add
;; Both of these can be optimized, including $B which reads from $A.
(global.get $B)
(global.get $A)
))

;; CHECK: (global $D (ref string) (string.const "foo"))
(global $D (ref string) (string.const "foo"))

;; CHECK: (global $E (ref string) (string.const "foo"))
(global $E (ref string) (global.get $D))
;; CHECK: (global $E (ref string) (string.const "bar"))
(global $E (ref string) (string.const "bar"))

;; CHECK: (global $G (ref $struct) (struct.new $struct
;; CHECK-NEXT: (string.const "foo")
;; CHECK-NEXT: (string.const "bar")
;; CHECK-NEXT: ))
(global $G (ref $struct) (struct.new $struct
(global.get $D)
(global.get $E)
))

;; CHECK: (func $test (type $0)
;; CHECK: (func $test (type $1)
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (global.get $A)
;; CHECK-NEXT: )
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9 changes: 7 additions & 2 deletions test/lit/passes/simplify-globals-nested.wast
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Expand Up @@ -6,8 +6,11 @@
;; Test that we propagate globals into nested children of other globals.

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

;; CHECK: (import "x" "y" (global $no i32))
(import "x" "y" (global $no i32))

;; CHECK: (global $a i32 (i32.const 42))
(global $a i32 (i32.const 42))
Expand All @@ -17,10 +20,12 @@

;; CHECK: (global $struct (ref $struct) (struct.new $struct
;; CHECK-NEXT: (i32.const 42)
;; CHECK-NEXT: (global.get $no)
;; CHECK-NEXT: (i32.const 1337)
;; CHECK-NEXT: ))
(global $struct (ref $struct) (struct.new $struct
(global.get $a)
(global.get $no) ;; the middle item cannot be optimized
(global.get $b)
))
)
Expand Down