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DCE: Fix old EH on a pop that gets moved in a catch body #6400

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merged 1 commit into from
Mar 14, 2024
Merged

DCE: Fix old EH on a pop that gets moved in a catch body #6400

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32 changes: 25 additions & 7 deletions src/passes/DeadCodeElimination.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -28,13 +28,14 @@
// have no side effects.
//

#include <ir/iteration.h>
#include <ir/properties.h>
#include <ir/type-updating.h>
#include <pass.h>
#include <vector>
#include <wasm-builder.h>
#include <wasm.h>
#include "ir/eh-utils.h"
#include "ir/iteration.h"
#include "ir/properties.h"
#include "ir/type-updating.h"
#include "pass.h"
#include "vector"
#include "wasm-builder.h"
#include "wasm.h"

namespace wasm {

Expand Down Expand Up @@ -89,7 +90,11 @@ struct DeadCodeElimination
Builder builder(*getModule());
std::vector<Expression*> remainingChildren;
bool afterUnreachable = false;
bool hasPop = false;
for (auto* child : ChildIterator(curr)) {
if (child->is<Pop>()) {
hasPop = true;
}
if (afterUnreachable) {
typeUpdater.noteRecursiveRemoval(child);
continue;
Expand All @@ -105,6 +110,11 @@ struct DeadCodeElimination
replaceCurrent(remainingChildren[0]);
} else {
replaceCurrent(builder.makeBlock(remainingChildren));
if (hasPop) {
// We are moving a pop into a new block we just created, which
// means we may need to fix things up here.
needEHFixups = true;
}
}
}
}
Expand Down Expand Up @@ -179,6 +189,14 @@ struct DeadCodeElimination
WASM_UNREACHABLE("unimplemented DCE control flow structure");
}
}

bool needEHFixups = false;

void visitFunction(Function* curr) {
if (needEHFixups) {
EHUtils::handleBlockNestedPops(curr, *getModule());
}
}
};

Pass* createDeadCodeEliminationPass() { return new DeadCodeElimination(); }
Expand Down
56 changes: 54 additions & 2 deletions test/lit/passes/dce-eh-old.wast
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Original file line number Diff line number Diff line change
Expand Up @@ -5,13 +5,15 @@
;; reachable
(module
;; CHECK: (tag $e)
(tag $e)

;; CHECK: (tag $e-i32 (param i32))
(tag $e-i32 (param i32))

;; CHECK: (func $foo (type $0)
;; CHECK-NEXT: (nop)
;; CHECK-NEXT: )
(func $foo)
(tag $e)


;; CHECK: (func $try_unreachable (type $0)
;; CHECK-NEXT: (try $try
Expand Down Expand Up @@ -130,4 +132,54 @@
)
)
)

;; CHECK: (func $call-pop-catch (type $0)
;; CHECK-NEXT: (local $0 i32)
;; CHECK-NEXT: (block $label
;; CHECK-NEXT: (try $try
;; CHECK-NEXT: (do
;; CHECK-NEXT: (nop)
;; CHECK-NEXT: )
;; CHECK-NEXT: (catch $e-i32
;; CHECK-NEXT: (local.set $0
;; CHECK-NEXT: (pop i32)
;; CHECK-NEXT: )
;; CHECK-NEXT: (block
;; CHECK-NEXT: (block
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (local.get $0)
;; CHECK-NEXT: )
;; CHECK-NEXT: (br $label)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
(func $call-pop-catch
(block $label
(try
(do
(nop)
)
(catch $e-i32
;; This call is unreachable and can be removed. The pop, however, must
;; be carefully handled while we do so, to not break validation.
(call $helper-i32-i32
(pop i32)
(br $label)
)
(nop)
)
)
)
)

;; CHECK: (func $helper-i32-i32 (type $2) (param $0 i32) (param $1 i32)
;; CHECK-NEXT: (nop)
;; CHECK-NEXT: )
(func $helper-i32-i32 (param $0 i32) (param $1 i32)
(nop)
)
)

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