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[FunctionAttrs] Don't bail out on unknown calls #150958

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Merged
merged 2 commits into from
Jul 29, 2025
Merged

[FunctionAttrs] Don't bail out on unknown calls #150958

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ee41e32
[FunctionAttrs] Don't bail out on unknown calls
nikic Jul 28, 2025
62e8ffe
drop norecurse change for now
nikic Jul 29, 2025
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34 changes: 6 additions & 28 deletions llvm/lib/Transforms/IPO/FunctionAttrs.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1863,7 +1863,6 @@ void AttributeInferer::run(const SCCNodeSet &SCCNodes,

struct SCCNodesResult {
SCCNodeSet SCCNodes;
bool HasUnknownCall;
};

} // end anonymous namespace
Expand Down Expand Up @@ -2227,29 +2226,13 @@ static void addWillReturn(const SCCNodeSet &SCCNodes,

static SCCNodesResult createSCCNodeSet(ArrayRef<Function *> Functions) {
SCCNodesResult Res;
Res.HasUnknownCall = false;
for (Function *F : Functions) {
if (!F || F->hasOptNone() || F->hasFnAttribute(Attribute::Naked) ||
F->isPresplitCoroutine()) {
// Treat any function we're trying not to optimize as if it were an
// indirect call and omit it from the node set used below.
Res.HasUnknownCall = true;
// Omit any functions we're trying not to optimize from the set.
continue;
}
// Track whether any functions in this SCC have an unknown call edge.
// Note: if this is ever a performance hit, we can common it with
// subsequent routines which also do scans over the instructions of the
// function.
if (!Res.HasUnknownCall) {
for (Instruction &I : instructions(*F)) {
if (auto *CB = dyn_cast<CallBase>(&I)) {
if (!CB->getCalledFunction()) {
Res.HasUnknownCall = true;
break;
}
}
}
}

Res.SCCNodes.insert(F);
}
return Res;
Expand Down Expand Up @@ -2282,15 +2265,10 @@ deriveAttrsInPostOrder(ArrayRef<Function *> Functions, AARGetterT &&AARGetter,
addColdAttrs(Nodes.SCCNodes, Changed);
addWillReturn(Nodes.SCCNodes, Changed);
addNoUndefAttrs(Nodes.SCCNodes, Changed);

// If we have no external nodes participating in the SCC, we can deduce some
// more precise attributes as well.
if (!Nodes.HasUnknownCall) {
addNoAliasAttrs(Nodes.SCCNodes, Changed);
addNonNullAttrs(Nodes.SCCNodes, Changed);
inferAttrsFromFunctionBodies(Nodes.SCCNodes, Changed);
addNoRecurseAttrs(Nodes.SCCNodes, Changed);
}
addNoAliasAttrs(Nodes.SCCNodes, Changed);
addNonNullAttrs(Nodes.SCCNodes, Changed);
inferAttrsFromFunctionBodies(Nodes.SCCNodes, Changed);
addNoRecurseAttrs(Nodes.SCCNodes, Changed);

// Finally, infer the maximal set of attributes from the ones we've inferred
// above. This is handling the cases where one attribute on a signature
Expand Down
2 changes: 1 addition & 1 deletion llvm/test/Transforms/FunctionAttrs/noalias.ll
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Expand Up @@ -235,7 +235,7 @@ define ptr @return_unknown_call(ptr %fn) {
}

define ptr @return_unknown_noalias_call(ptr %fn) {
; CHECK-LABEL: define ptr @return_unknown_noalias_call(
; CHECK-LABEL: define noalias ptr @return_unknown_noalias_call(
; CHECK-SAME: ptr readonly captures(none) [[FN:%.*]]) {
; CHECK-NEXT: [[A:%.*]] = call noalias ptr [[FN]]()
; CHECK-NEXT: ret ptr [[A]]
Expand Down
2 changes: 1 addition & 1 deletion llvm/test/Transforms/FunctionAttrs/nonnull.ll
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Expand Up @@ -1412,7 +1412,7 @@ define ptr @unknown_func(ptr %fn) {
}

define ptr @unknown_nonnull_func(ptr %fn) {
; FNATTRS-LABEL: define ptr @unknown_nonnull_func(
; FNATTRS-LABEL: define nonnull ptr @unknown_nonnull_func(
; FNATTRS-SAME: ptr readonly captures(none) [[FN:%.*]]) {
; FNATTRS-NEXT: [[RES:%.*]] = call nonnull ptr [[FN]]()
; FNATTRS-NEXT: ret ptr [[RES]]
Expand Down
5 changes: 3 additions & 2 deletions llvm/test/Transforms/FunctionAttrs/nounwind.ll
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Expand Up @@ -418,9 +418,10 @@ define void @unknown_call(ptr %fn) {
}

define void @unknown_nounwind_call(ptr %fn) {
; FNATTRS: Function Attrs: nounwind
; FNATTRS-LABEL: define {{[^@]+}}@unknown_nounwind_call
; FNATTRS-SAME: (ptr readonly captures(none) [[FN:%.*]]) {
; FNATTRS-NEXT: call void [[FN]]() #[[ATTR2:[0-9]+]]
; FNATTRS-SAME: (ptr readonly captures(none) [[FN:%.*]]) #[[ATTR2:[0-9]+]] {
; FNATTRS-NEXT: call void [[FN]]() #[[ATTR2]]
; FNATTRS-NEXT: ret void
;
; ATTRIBUTOR: Function Attrs: nounwind
Expand Down