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[LTT] Mark as unkown weak function tests. #167399

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[LTT] Mark as unkown weak function tests. #167399

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3 changes: 3 additions & 0 deletions llvm/lib/Transforms/IPO/LowerTypeTests.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1493,6 +1493,9 @@ void LowerTypeTestsModule::replaceWeakDeclarationWithJumpTablePtr(
Constant::getNullValue(F->getType()));
Value *Select = Builder.CreateSelect(ICmp, JT,
Constant::getNullValue(F->getType()));

if (auto *SI = dyn_cast<SelectInst>(Select))
setExplicitlyUnknownBranchWeightsIfProfiled(*SI, DEBUG_TYPE);
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@mtrofin mtrofin Nov 10, 2025

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@pcc a question - would it be technically possible to propagate information about the weak function from [thin]link over to this point, and thus know if we even need a select in the first place?

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@teresajohnson teresajohnson Nov 14, 2025

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I would just add a TODO to consider that.

// For phi nodes, we need to update the incoming value for all operands
// with the same predecessor.
if (PN)
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5 changes: 3 additions & 2 deletions llvm/test/Transforms/LowerTypeTests/function-weak.ll
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Expand Up @@ -32,10 +32,10 @@ target triple = "x86_64-unknown-linux-gnu"
declare !type !0 extern_weak void @f()

; CHECK: define zeroext i1 @check_f()
define zeroext i1 @check_f() {
define zeroext i1 @check_f() !prof !{!"function_entry_count", i32 10} {
entry:
; CHECK: [[CMP:%.*]] = icmp ne ptr @f, null
; CHECK: [[SEL:%.*]] = select i1 [[CMP]], ptr @[[JT:.*]], ptr null
; CHECK: [[SEL:%.*]] = select i1 [[CMP]], ptr @[[JT:.*]], ptr null, !prof ![[SELPROF:[0-9]+]]
; CHECK: [[PTI:%.*]] = ptrtoint ptr [[SEL]] to i1
; CHECK: ret i1 [[PTI]]
ret i1 ptrtoint (ptr @f to i1)
Expand Down Expand Up @@ -165,3 +165,4 @@ define i1 @foo(ptr %p) {
; CHECK-NEXT: }

!0 = !{i32 0, !"typeid1"}
; CHECK: ![[SELPROF]] = !{!"unknown", !"lowertypetests"}
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