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Add support for llvm.dbg.declare_value in the CoroSplitter pass. #168134

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Nov 24, 2025
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Add support for llvm.dbg.declare_value in the CoroSplitter pass. #168134

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66 changes: 61 additions & 5 deletions llvm/lib/Transforms/Coroutines/CoroFrame.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -554,6 +554,7 @@ static void cacheDIVar(FrameDataInfo &FrameData,
DIVarCache.insert({V, (*I)->getVariable()});
};
CacheIt(findDVRDeclares(V));
CacheIt(findDVRDeclareValues(V));
}
}

Expand Down Expand Up @@ -1142,6 +1143,47 @@ static void insertSpills(const FrameDataInfo &FrameData, coro::Shape &Shape) {
for_each(DVRs, SalvageOne);
}

TinyPtrVector<DbgVariableRecord *> DVRDeclareValues =
findDVRDeclareValues(Def);
// Try best to find dbg.declare_value. If the spill is a temp, there may
// not be a direct dbg.declare_value. Walk up the load chain to find one
// from an alias.
if (F->getSubprogram()) {
auto *CurDef = Def;
while (DVRDeclareValues.empty() && isa<LoadInst>(CurDef)) {
auto *LdInst = cast<LoadInst>(CurDef);
// Only consider ptr to ptr same type load.
if (LdInst->getPointerOperandType() != LdInst->getType())
break;
CurDef = LdInst->getPointerOperand();
if (!isa<AllocaInst, LoadInst>(CurDef))
break;
DVRDeclareValues = findDVRDeclareValues(CurDef);
}
}

auto SalvageOneCoro = [&](auto *DDI) {
// This dbg.declare_value is preserved for all coro-split function
// fragments. It will be unreachable in the main function, and
// processed by coro::salvageDebugInfo() by the Cloner. However, convert
// it to a dbg.declare to make sure future passes don't have to deal
// with a dbg.declare_value.
auto *VAM = ValueAsMetadata::get(CurrentReload);
Type *Ty = VAM->getValue()->getType();
// If the metadata type is not a pointer, emit a dbg.value instead.
DbgVariableRecord *NewDVR = new DbgVariableRecord(
ValueAsMetadata::get(CurrentReload), DDI->getVariable(),
DDI->getExpression(), DDI->getDebugLoc(),
Ty->isPointerTy() ? DbgVariableRecord::LocationType::Declare
: DbgVariableRecord::LocationType::Value);
Builder.GetInsertPoint()->getParent()->insertDbgRecordBefore(
NewDVR, Builder.GetInsertPoint());
// This dbg.declare_value is for the main function entry point. It
// will be deleted in all coro-split functions.
coro::salvageDebugInfo(ArgToAllocaMap, *DDI, false /*UseEntryValue*/);
};
for_each(DVRDeclareValues, SalvageOneCoro);

// If we have a single edge PHINode, remove it and replace it with a
// reload from the coroutine frame. (We already took care of multi edge
// PHINodes by normalizing them in the rewritePHIs function).
Expand Down Expand Up @@ -1925,7 +1967,7 @@ void coro::salvageDebugInfo(
Function *F = DVR.getFunction();
// Follow the pointer arithmetic all the way to the incoming
// function argument and convert into a DIExpression.
bool SkipOutermostLoad = DVR.isDbgDeclare();
bool SkipOutermostLoad = DVR.isDbgDeclare() || DVR.isDbgDeclareValue();
Value *OriginalStorage = DVR.getVariableLocationOp(0);

auto SalvagedInfo =
Expand All @@ -1939,10 +1981,11 @@ void coro::salvageDebugInfo(

DVR.replaceVariableLocationOp(OriginalStorage, Storage);
DVR.setExpression(Expr);
// We only hoist dbg.declare today since it doesn't make sense to hoist
// dbg.value since it does not have the same function wide guarantees that
// dbg.declare does.
if (DVR.getType() == DbgVariableRecord::LocationType::Declare) {
// We only hoist dbg.declare and dbg.declare_value today since it doesn't make
// sense to hoist dbg.value since it does not have the same function wide
// guarantees that dbg.declare does.
if (DVR.getType() == DbgVariableRecord::LocationType::Declare ||
DVR.getType() == DbgVariableRecord::LocationType::DeclareValue) {
std::optional<BasicBlock::iterator> InsertPt;
if (auto *I = dyn_cast<Instruction>(Storage)) {
InsertPt = I->getInsertionPointAfterDef();
Expand All @@ -1957,6 +2000,19 @@ void coro::salvageDebugInfo(
InsertPt = F->getEntryBlock().begin();
if (InsertPt) {
DVR.removeFromParent();
// If there is a dbg.declare_value being reinserted, insert it as a
// dbg.declare instead, so that subsequent passes don't have to deal with
// a dbg.declare_value.
if (DVR.getType() == DbgVariableRecord::LocationType::DeclareValue) {
auto *MD = DVR.getRawLocation();
if (auto *VAM = dyn_cast<ValueAsMetadata>(MD)) {
Type *Ty = VAM->getValue()->getType();
if (Ty->isPointerTy())
DVR.Type = DbgVariableRecord::LocationType::Declare;
else
DVR.Type = DbgVariableRecord::LocationType::Value;
}
}
(*InsertPt)->getParent()->insertDbgRecordBefore(&DVR, *InsertPt);
}
}
Expand Down
68 changes: 68 additions & 0 deletions llvm/test/Transforms/Coroutines/declare-value.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,68 @@
;RUN: opt -mtriple='arm64-' %s -S -passes='module(coro-early),cgscc(coro-split,simplifycfg)' -o - | FileCheck %s

; CHECK: %.debug = alloca double, align 8
; CHECK-NEXT: #dbg_declare(ptr %{{.*}}, !{{[0-9]+}}, !DIExpression(DW_OP_deref), !{{[0-9]+}})
; CHECK-NEXT: store double %{{[0-9]+}}, ptr %{{.*}}, align 8
; CHECK-NEXT: #dbg_declare(ptr %arg, !{{[0-9]+}}, !DIExpression(DW_OP_plus_uconst, 24), !{{[0-9]+}})

; ModuleID = '/Users/srastogi/Development/llvm-project-2/llvm/test/Transforms/Coroutines/declare-value.ll'
source_filename = "/Users/srastogi/Development/llvm-project-2/llvm/test/Transforms/Coroutines/declare-value.ll"
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128-Fn32"
target triple = "arm64-unknown"

@coroutineATu = global <{ i32, i32 }> <{ i32 trunc (i64 sub (i64 ptrtoint (ptr @coroutineA to i64), i64 ptrtoint (ptr @coroutineATu to i64)) to i32), i32 16 }>, align 8

; Function Attrs: presplitcoroutine
define swifttailcc void @coroutineA(ptr swiftasync %arg, double %0) #0 !dbg !1 {
%var_with_dbg_value = alloca ptr, align 8
%var_with_dbg_declare = alloca ptr, align 8
#dbg_declare(ptr %var_with_dbg_declare, !5, !DIExpression(), !7)
#dbg_declare_value(double %0, !5, !DIExpression(), !7)
%i2 = call token @llvm.coro.id.async(i32 16, i32 16, i32 0, ptr nonnull @coroutineATu)
%i3 = call ptr @llvm.coro.begin(token %i2, ptr null)
%i7 = call ptr @llvm.coro.async.resume(), !dbg !7
%i10 = call { ptr } (i32, ptr, ptr, ...) @llvm.coro.suspend.async.sl_p0s(i32 0, ptr %i7, ptr nonnull @__swift_async_resume_get_context, ptr nonnull @coroutineA.1, ptr %i7, i64 0, i64 0, ptr %arg), !dbg !7
call void @dont_optimize(ptr %var_with_dbg_value, ptr %var_with_dbg_declare), !dbg !7
unreachable, !dbg !7
}

define weak_odr hidden ptr @__swift_async_resume_get_context(ptr %arg) !dbg !8 {
ret ptr %arg, !dbg !9
}

define hidden swifttailcc void @coroutineA.1(ptr %arg, i64 %arg1, i64 %arg2, ptr %arg3) !dbg !10 {
ret void, !dbg !11
}

declare void @dont_optimize(ptr, ptr)

; Function Attrs: nomerge nounwind
declare ptr @llvm.coro.async.resume() #1

; Function Attrs: nounwind
declare ptr @llvm.coro.begin(token, ptr writeonly) #2

; Function Attrs: nounwind
declare token @llvm.coro.id.async(i32, i32, i32, ptr) #2

; Function Attrs: nomerge nounwind
declare { ptr } @llvm.coro.suspend.async.sl_p0s(i32, ptr, ptr, ...) #1

attributes #0 = { presplitcoroutine }
attributes #1 = { nomerge nounwind }
attributes #2 = { nounwind }

!llvm.module.flags = !{!0}

!0 = !{i32 2, !"Debug Info Version", i32 3}
!1 = distinct !DISubprogram(scope: null, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !4)
!2 = distinct !DICompileUnit(language: DW_LANG_Swift, file: !3, isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
!3 = !DIFile(filename: "blah", directory: "")
!4 = !{}
!5 = !DILocalVariable(scope: !1, type: !6)
!6 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "Klass")
!7 = !DILocation(line: 0, scope: !1)
!8 = distinct !DISubprogram(scope: null, spFlags: DISPFlagDefinition, unit: !2)
!9 = !DILocation(line: 0, scope: !8)
!10 = distinct !DISubprogram(scope: null, spFlags: DISPFlagDefinition, unit: !2)
!11 = !DILocation(line: 0, scope: !10)