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SimplifyGlobals: Constant-propagate constant values of immutable globals (#2234)
1 parent 9bdf713 commit 8d3bc3f

9 files changed

Lines changed: 138 additions & 12 deletions

‎src/passes/SimplifyGlobals.cpp‎

Lines changed: 43 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -21,10 +21,12 @@
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// globals immutable.
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// * If an immutable global is a copy of another, use the earlier one,
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// to allow removal of the copies later.
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// * Apply the constant values of immutable globals.
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//
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#include <atomic>
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#include "ir/utils.h"
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#include "pass.h"
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#include "wasm.h"
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@@ -54,6 +56,7 @@ struct GlobalUseScanner : public WalkerPass<PostWalker<GlobalUseScanner>> {
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};
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using NameNameMap = std::map<Name, Name>;
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using NameSet = std::set<Name>;
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struct GlobalUseModifier : public WalkerPass<PostWalker<GlobalUseModifier>> {
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bool isFunctionParallel() override { return true; }
@@ -76,6 +79,29 @@ struct GlobalUseModifier : public WalkerPass<PostWalker<GlobalUseModifier>> {
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NameNameMap* copiedParentMap;
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};
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82+
struct ConstantGlobalApplier
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: public WalkerPass<PostWalker<ConstantGlobalApplier>> {
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bool isFunctionParallel() override { return true; }
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ConstantGlobalApplier(NameSet* constantGlobals)
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: constantGlobals(constantGlobals) {}
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ConstantGlobalApplier* create() override {
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return new ConstantGlobalApplier(constantGlobals);
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}
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void visitGlobalGet(GlobalGet* curr) {
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if (constantGlobals->count(curr->name)) {
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auto* global = getModule()->getGlobal(curr->name);
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assert(global->init->is<Const>());
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replaceCurrent(ExpressionManipulator::copy(global->init, *getModule()));
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}
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}
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private:
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NameSet* constantGlobals;
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};
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} // anonymous namespace
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struct SimplifyGlobals : public Pass {
@@ -135,6 +161,23 @@ struct SimplifyGlobals : public Pass {
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subRunner.add<GlobalUseModifier>(&copiedParentMap);
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subRunner.run();
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}
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// If any immutable globals have constant values, we can just apply them
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// (the global itself will be removed by another pass, as it/ won't have
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// any uses).
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NameSet constantGlobals;
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for (auto& global : module->globals) {
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if (!global->mutable_ && !global->imported() &&
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global->init->is<Const>()) {
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constantGlobals.insert(global->name);
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}
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}
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if (!constantGlobals.empty()) {
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PassRunner subRunner(module, runner->options);
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subRunner.add<ConstantGlobalApplier>(&constantGlobals);
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subRunner.run();
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}
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// TODO a mutable global's initial value can be applied to another global
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// after it, as the mutable one can't mutate during instance startup
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}
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};
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‎test/min.fromasm‎

Lines changed: 1 addition & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,6 @@
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(import "env" "memory" (memory $memory 256 256))
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(data (global.get $__memory_base) "min.asm.js")
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(import "env" "__memory_base" (global $__memory_base i32))
5-
(global $M i32 (i32.const 0))
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(export "floats" (func $floats))
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(export "getTempRet0" (func $ub))
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(export "neg" (func $neg))
@@ -35,6 +34,6 @@
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(drop
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(call $ub)
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)
38-
(global.get $M)
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(i32.const 0)
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)
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)

‎test/min.fromasm.clamp‎

Lines changed: 1 addition & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,6 @@
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(import "env" "memory" (memory $memory 256 256))
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(data (global.get $__memory_base) "min.asm.js")
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(import "env" "__memory_base" (global $__memory_base i32))
5-
(global $M i32 (i32.const 0))
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(export "floats" (func $floats))
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(export "getTempRet0" (func $ub))
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(export "neg" (func $neg))
@@ -35,6 +34,6 @@
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(drop
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(call $ub)
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)
38-
(global.get $M)
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(i32.const 0)
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)
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)

‎test/min.fromasm.imprecise‎

Lines changed: 1 addition & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,5 @@
11
(module
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(import "env" "memory" (memory $memory 256 256))
3-
(global $M i32 (i32.const 0))
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(export "floats" (func $floats))
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(export "getTempRet0" (func $ub))
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(export "neg" (func $neg))
@@ -33,6 +32,6 @@
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(drop
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(call $ub)
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)
36-
(global.get $M)
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(i32.const 0)
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)
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)

‎test/passes/simplify-globals_enable-mutable-globals.txt‎

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Original file line numberDiff line numberDiff line change
@@ -51,3 +51,62 @@
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(global $g2 (mut i32) (global.get $g1))
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(export "global-2" (global $g2))
5353
)
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(module
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(type $FUNCSIG$v (func))
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(global $g1 i32 (i32.const 1))
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(global $g2 i32 (global.get $g1))
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(global $g3 f64 (f64.const -3.4))
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(global $g4 f64 (f64.const -2.8))
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(global $g5 i32 (i32.const 2))
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(global $g6 i32 (global.get $g5))
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(global $g7 i32 (i32.const 3))
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(global $g8 i32 (global.get $g7))
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(global $g9 i32 (i32.const 4))
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(global $ga (mut i32) (global.get $g9))
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(global $gb (mut i32) (i32.const 5))
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(global $gc i32 (global.get $gb))
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(func $foo (; 0 ;) (type $FUNCSIG$v)
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(drop
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(i32.const 1)
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)
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(drop
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(i32.const 1)
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)
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(drop
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(f64.const -3.4)
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)
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(drop
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(f64.const -2.8)
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)
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(drop
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(i32.const 2)
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)
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(drop
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(i32.const 2)
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)
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(drop
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(i32.const 3)
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)
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(drop
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(i32.const 3)
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)
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(drop
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(i32.const 4)
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)
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(drop
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(global.get $ga)
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)
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(drop
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(global.get $gb)
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)
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(drop
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(global.get $gc)
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)
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(global.set $ga
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(i32.const 6)
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)
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(global.set $gb
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(i32.const 7)
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)
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)
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)

‎test/passes/simplify-globals_enable-mutable-globals.wast‎

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@@ -34,4 +34,34 @@
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(global $g2 (mut i32) (global.get $g1))
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(export "global-2" (global $g2))
3636
)
37+
(module
38+
(global $g1 i32 (i32.const 1))
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(global $g2 i32 (global.get $g1))
40+
(global $g3 f64 (f64.const -3.4))
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(global $g4 (mut f64) (f64.const -2.8))
42+
(global $g5 i32 (i32.const 2))
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(global $g6 (mut i32) (global.get $g5))
44+
(global $g7 (mut i32) (i32.const 3))
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(global $g8 i32 (global.get $g7))
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(global $g9 i32 (i32.const 4))
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(global $ga (mut i32) (global.get $g9))
48+
(global $gb (mut i32) (i32.const 5))
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(global $gc i32 (global.get $gb))
50+
(func $foo
51+
(drop (global.get $g1))
52+
(drop (global.get $g2))
53+
(drop (global.get $g3))
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(drop (global.get $g4))
55+
(drop (global.get $g5))
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(drop (global.get $g6))
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(drop (global.get $g7))
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(drop (global.get $g8))
59+
(drop (global.get $g9))
60+
(drop (global.get $ga))
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(drop (global.get $gb))
62+
(drop (global.get $gc))
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(global.set $ga (i32.const 6))
64+
(global.set $gb (i32.const 7))
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)
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)
3767

‎test/unit.fromasm‎

Lines changed: 1 addition & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -24,7 +24,6 @@
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(import "asm2wasm" "f64-to-int" (func $f64-to-int (param f64) (result i32)))
2525
(import "asm2wasm" "f64-rem" (func $f64-rem (param f64 f64) (result f64)))
2626
(global $Int (mut i32) (i32.const 0))
27-
(global $Double f64 (f64.const 0))
2827
(global $nonZero (mut i32) (i32.const 1337))
2928
(global $exportedNumber i32 (i32.const 42))
3029
(export "big_negative" (func $big_negative))
@@ -92,7 +91,7 @@
9291
)
9392
(if
9493
(f64.gt
95-
(global.get $Double)
94+
(f64.const 0)
9695
(f64.const 0)
9796
)
9897
(return

‎test/unit.fromasm.clamp‎

Lines changed: 1 addition & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -22,7 +22,6 @@
2222
(import "env" "emscripten_log" (func $emscripten_log))
2323
(import "asm2wasm" "f64-rem" (func $f64-rem (param f64 f64) (result f64)))
2424
(global $Int (mut i32) (i32.const 0))
25-
(global $Double f64 (f64.const 0))
2625
(global $nonZero (mut i32) (i32.const 1337))
2726
(global $exportedNumber i32 (i32.const 42))
2827
(export "big_negative" (func $big_negative))
@@ -90,7 +89,7 @@
9089
)
9190
(if
9291
(f64.gt
93-
(global.get $Double)
92+
(f64.const 0)
9493
(f64.const 0)
9594
)
9695
(return

‎test/unit.fromasm.imprecise‎

Lines changed: 1 addition & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -20,7 +20,6 @@
2020
(import "env" "emscripten_log" (func $emscripten_log))
2121
(import "asm2wasm" "f64-rem" (func $f64-rem (param f64 f64) (result f64)))
2222
(global $Int (mut i32) (i32.const 0))
23-
(global $Double f64 (f64.const 0))
2423
(global $nonZero (mut i32) (i32.const 1337))
2524
(global $exportedNumber i32 (i32.const 42))
2625
(export "big_negative" (func $big_negative))
@@ -88,7 +87,7 @@
8887
)
8988
(if
9089
(f64.gt
91-
(global.get $Double)
90+
(f64.const 0)
9291
(f64.const 0)
9392
)
9493
(return

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