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Improve indirect call effects in GlobalEffects #8644

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dfc82c8
Account for addressed funcs
stevenfontanella Apr 19, 2026
f670a0d
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stevenfontanella Apr 20, 2026
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Fix comment
stevenfontanella Apr 23, 2026
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62 changes: 59 additions & 3 deletions src/passes/GlobalEffects.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@
#include <ranges>

#include "ir/effects.h"
#include "ir/element-utils.h"
#include "ir/module-utils.h"
#include "pass.h"
#include "support/graph_traversal.h"
Expand All @@ -47,6 +48,56 @@ struct FuncInfo {
std::unordered_set<HeapType> indirectCalledTypes;
};

/*
Only funcs that are 'addressed' may be the target of an indirect call. A
function is addressed if:
- It appears in a ref.func expression
- It appears in an `elem` segment (note that we already ignore `elem declare`
statements in our IR, but we check separately for funcs that appear in
`ref.func`).
- It's exported, because it may flow back to us as a reference.
- It's imported, which implies it is `elem declare`d.

If a function doesn't meet any of these criteria, it can't be the target of
an indirect call and we don't need to include its effects in indirect calls.
*/
std::unordered_set<Function*> getAddressedFuncs(Module& module) {
struct AddressedFuncsWalker : PostWalker<AddressedFuncsWalker> {
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@tlively tlively Apr 24, 2026

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Might as well make this a WalkerPass so it can be run on all the functions in parallel. Then instead of walkModule below, you would use walkModuleCode. Alternatively you could use ModuleUtils::ParallelFunctionAnalysis + walkModuleCode.

std::unordered_set<Function*>& addressedFuncs;

AddressedFuncsWalker(std::unordered_set<Function*>& addressedFuncs)
: addressedFuncs(addressedFuncs) {}

void visitRefFunc(RefFunc* refFunc) {
addressedFuncs.insert(getModule()->getFunction(refFunc->func));
}
};

std::unordered_set<Function*> addressedFuncs;
AddressedFuncsWalker walker(addressedFuncs);
walker.walkModule(&module);

ModuleUtils::iterImportedFunctions(
module, [&addressedFuncs, &module](Function* import) {
addressedFuncs.insert(module.getFunction(import->name));
});

for (const auto& export_ : module.exports) {
if (export_->kind != ExternalKind::Function) {
continue;
}

addressedFuncs.insert(module.getFunction(*export_->getInternalName()));
}

ElementUtils::iterAllElementFunctionNames(
&module, [&addressedFuncs, &module](Name func) {
addressedFuncs.insert(module.getFunction(func));
});
Comment on lines +93 to +96
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@tlively tlively Apr 24, 2026

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No need to do this separately. Walking the module code will already walk all the element segments and find the RefFunc expressions inside them.


return addressedFuncs;
}

std::map<Function*, FuncInfo> analyzeFuncs(Module& module,
const PassOptions& passOptions) {
ModuleUtils::ParallelFunctionAnalysis<FuncInfo> analysis(
Expand Down Expand Up @@ -146,6 +197,7 @@ using CallGraph =

CallGraph buildCallGraph(const Module& module,
const std::map<Function*, FuncInfo>& funcInfos,
const std::unordered_set<Function*>& addressedFuncs,
bool closedWorld) {
CallGraph callGraph;
if (!closedWorld) {
Expand Down Expand Up @@ -181,7 +233,9 @@ CallGraph buildCallGraph(const Module& module,
}

// Type -> Function
callGraph[caller->type.getHeapType()].insert(caller);
if (addressedFuncs.contains(caller)) {
callGraph[caller->type.getHeapType()].insert(caller);
}
}

// Type -> Type
Expand Down Expand Up @@ -345,8 +399,10 @@ struct GenerateGlobalEffects : public Pass {
std::map<Function*, FuncInfo> funcInfos =
analyzeFuncs(*module, getPassOptions());

auto callGraph =
buildCallGraph(*module, funcInfos, getPassOptions().closedWorld);
auto addressedFuncs = getAddressedFuncs(*module);

auto callGraph = buildCallGraph(
*module, funcInfos, addressedFuncs, getPassOptions().closedWorld);

propagateEffects(*module, getPassOptions(), funcInfos, callGraph);

Expand Down
7 changes: 2 additions & 5 deletions test/lit/passes/global-effects-closed-world.wast
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Original file line number Diff line number Diff line change
Expand Up @@ -329,15 +329,12 @@
)

;; CHECK: (func $f (type $1) (param $ref (ref $only-has-effects-in-not-addressable-function))
;; CHECK-NEXT: (call $calls-type-with-effects-but-not-addressable
;; CHECK-NEXT: (local.get $ref)
;; CHECK-NEXT: )
;; CHECK-NEXT: (nop)
;; CHECK-NEXT: )
(func $f (param $ref (ref $only-has-effects-in-not-addressable-function))
;; The type $has-effects-but-not-exported doesn't have an address because
;; it's not exported and it's never the target of a ref.func.
;; We should be able to determine that $ref can only point to $nop.
;; TODO: Only aggregate effects from functions that are addressed.
;; So the call_ref has no potential targets and thus no effects.
(call $calls-type-with-effects-but-not-addressable (local.get $ref))
)
)
Expand Down
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