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Fix effect analysis in presence of tail calls within try blocks #6463

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Fix effect analysis in presence of tail calls within try blocks #6463

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6c08857
Example: throw incorrectly optimized away
vouillon Mar 30, 2024
02467dd
Fix effect analysis in presence of tail calls within try blocks
vouillon Apr 2, 2024
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11 changes: 7 additions & 4 deletions src/ir/effects.h
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Original file line number Diff line number Diff line change
Expand Up @@ -478,7 +478,7 @@ class EffectAnalyzer {
// the target function throws and we know that will be caught anyhow,
// the same as the code below for the general path.
const auto& targetEffects = iter->second;
if (targetEffects.throws_ && parent.tryDepth > 0) {
if (targetEffects.throws_ && parent.tryDepth > 0 && !curr->isReturn) {
auto filteredEffects = targetEffects;
filteredEffects.throws_ = false;
parent.mergeIn(filteredEffects);
Expand All @@ -492,13 +492,15 @@ class EffectAnalyzer {

parent.calls = true;
// When EH is enabled, any call can throw.
if (parent.features.hasExceptionHandling() && parent.tryDepth == 0) {
if (parent.features.hasExceptionHandling() &&
(parent.tryDepth == 0 || curr->isReturn)) {
parent.throws_ = true;
}
}
void visitCallIndirect(CallIndirect* curr) {
parent.calls = true;
if (parent.features.hasExceptionHandling() && parent.tryDepth == 0) {
if (parent.features.hasExceptionHandling() &&
(parent.tryDepth == 0 || curr->isReturn)) {
parent.throws_ = true;
}
if (curr->isReturn) {
Expand Down Expand Up @@ -750,7 +752,8 @@ class EffectAnalyzer {
return;
}
parent.calls = true;
if (parent.features.hasExceptionHandling() && parent.tryDepth == 0) {
if (parent.features.hasExceptionHandling() &&
(parent.tryDepth == 0 || curr->isReturn)) {
parent.throws_ = true;
}
if (curr->isReturn) {
Expand Down
73 changes: 73 additions & 0 deletions test/lit/passes/global-effects.wast
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Original file line number Diff line number Diff line change
Expand Up @@ -450,4 +450,77 @@
(call $cycle-with-unknown-call)
(call $import)
)

;; WITHOUT: (func $throw-through-return-call (type $0)
;; WITHOUT-NEXT: (try $try
;; WITHOUT-NEXT: (do
;; WITHOUT-NEXT: (return_call $throw)
;; WITHOUT-NEXT: )
;; WITHOUT-NEXT: (catch_all
;; WITHOUT-NEXT: (nop)
;; WITHOUT-NEXT: )
;; WITHOUT-NEXT: )
;; WITHOUT-NEXT: )
;; INCLUDE: (func $throw-through-return-call (type $0)
;; INCLUDE-NEXT: (try $try
;; INCLUDE-NEXT: (do
;; INCLUDE-NEXT: (return_call $throw)
;; INCLUDE-NEXT: )
;; INCLUDE-NEXT: (catch_all
;; INCLUDE-NEXT: (nop)
;; INCLUDE-NEXT: )
;; INCLUDE-NEXT: )
;; INCLUDE-NEXT: )
;; DISCARD: (func $throw-through-return-call (type $0)
;; DISCARD-NEXT: (try $try
;; DISCARD-NEXT: (do
;; DISCARD-NEXT: (return_call $throw)
;; DISCARD-NEXT: )
;; DISCARD-NEXT: (catch_all
;; DISCARD-NEXT: (nop)
;; DISCARD-NEXT: )
;; DISCARD-NEXT: )
;; DISCARD-NEXT: )
(func $throw-through-return-call
;; The exception is not catched, so this code cannot be simplified
(try
(do
(return_call $throw)
)
(catch_all)
)
)

;; WITHOUT: (func $catch-all-effects (type $0)
;; WITHOUT-NEXT: (try $try
;; WITHOUT-NEXT: (do
;; WITHOUT-NEXT: (call $throw-through-return-call)
;; WITHOUT-NEXT: )
;; WITHOUT-NEXT: (catch_all
;; WITHOUT-NEXT: (nop)
;; WITHOUT-NEXT: )
;; WITHOUT-NEXT: )
;; WITHOUT-NEXT: )
;; INCLUDE: (func $catch-all-effects (type $0)
;; INCLUDE-NEXT: (nop)
;; INCLUDE-NEXT: )
;; DISCARD: (func $catch-all-effects (type $0)
;; DISCARD-NEXT: (try $try
;; DISCARD-NEXT: (do
;; DISCARD-NEXT: (call $throw-through-return-call)
;; DISCARD-NEXT: )
;; DISCARD-NEXT: (catch_all
;; DISCARD-NEXT: (nop)
;; DISCARD-NEXT: )
;; DISCARD-NEXT: )
;; DISCARD-NEXT: )
(func $catch-all-effects
;; The exception is catched, so the function body can be optimized away
(try
(do
(call $throw-through-return-call)
)
(catch_all)
)
)
)