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[StructurizeCFG] Stop setting DebugLocs in flow blocks #139088

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May 9, 2025
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[StructurizeCFG] Stop setting DebugLocs in flow blocks #139088

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65 changes: 20 additions & 45 deletions llvm/lib/Transforms/Scalar/StructurizeCFG.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -129,8 +129,6 @@ using BBPredicates = DenseMap<BasicBlock *, PredInfo>;
using PredMap = DenseMap<BasicBlock *, BBPredicates>;
using BB2BBMap = DenseMap<BasicBlock *, BasicBlock *>;

using BranchDebugLocMap = DenseMap<BasicBlock *, DebugLoc>;

// A traits type that is intended to be used in graph algorithms. The graph
// traits starts at an entry node, and traverses the RegionNodes that are in
// the Nodes set.
Expand Down Expand Up @@ -303,8 +301,6 @@ class StructurizeCFG {
PredMap LoopPreds;
BranchVector LoopConds;

BranchDebugLocMap TermDL;

RegionNode *PrevNode;

void orderNodes();
Expand Down Expand Up @@ -336,14 +332,14 @@ class StructurizeCFG {

void simplifyAffectedPhis();

void killTerminator(BasicBlock *BB);
DebugLoc killTerminator(BasicBlock *BB);

void changeExit(RegionNode *Node, BasicBlock *NewExit,
bool IncludeDominator);

BasicBlock *getNextFlow(BasicBlock *Dominator);

BasicBlock *needPrefix(bool NeedEmpty);
std::pair<BasicBlock *, DebugLoc> needPrefix(bool NeedEmpty);

BasicBlock *needPostfix(BasicBlock *Flow, bool ExitUseAllowed);

Expand All @@ -361,8 +357,6 @@ class StructurizeCFG {

void rebuildSSA();

void setDebugLoc(BranchInst *Br, BasicBlock *BB);

public:
void init(Region *R);
bool run(Region *R, DominatorTree *DT);
Expand Down Expand Up @@ -918,28 +912,18 @@ void StructurizeCFG::simplifyAffectedPhis() {
} while (Changed);
}

void StructurizeCFG::setDebugLoc(BranchInst *Br, BasicBlock *BB) {
auto I = TermDL.find(BB);
if (I == TermDL.end())
return;

Br->setDebugLoc(I->second);
TermDL.erase(I);
}

/// Remove phi values from all successors and then remove the terminator.
void StructurizeCFG::killTerminator(BasicBlock *BB) {
DebugLoc StructurizeCFG::killTerminator(BasicBlock *BB) {
Instruction *Term = BB->getTerminator();
if (!Term)
return;

if (const DebugLoc &DL = Term->getDebugLoc())
TermDL[BB] = DL;
return DebugLoc();

for (BasicBlock *Succ : successors(BB))
delPhiValues(BB, Succ);

DebugLoc DL = Term->getDebugLoc();
Term->eraseFromParent();
return DL;
}

/// Let node exit(s) point to NewExit
Expand Down Expand Up @@ -978,9 +962,9 @@ void StructurizeCFG::changeExit(RegionNode *Node, BasicBlock *NewExit,
SubRegion->replaceExit(NewExit);
} else {
BasicBlock *BB = Node->getNodeAs<BasicBlock>();
killTerminator(BB);
DebugLoc DL = killTerminator(BB);
BranchInst *Br = BranchInst::Create(NewExit, BB);
setDebugLoc(Br, BB);
Br->setDebugLoc(DL);
addPhiValues(BB, NewExit);
if (IncludeDominator)
DT->changeImmediateDominator(NewExit, BB);
Expand All @@ -995,29 +979,20 @@ BasicBlock *StructurizeCFG::getNextFlow(BasicBlock *Dominator) {
BasicBlock *Flow = BasicBlock::Create(Context, FlowBlockName,
Func, Insert);
FlowSet.insert(Flow);

if (auto *Term = Dominator->getTerminator()) {
if (const DebugLoc &DL = Term->getDebugLoc())
TermDL[Flow] = DL;
} else if (DebugLoc DLTemp = TermDL.lookup(Dominator)) {
// Use a temporary copy to avoid a use-after-free if the map's storage
// is reallocated.
TermDL[Flow] = DLTemp;
}

DT->addNewBlock(Flow, Dominator);
ParentRegion->getRegionInfo()->setRegionFor(Flow, ParentRegion);
return Flow;
}

/// Create a new or reuse the previous node as flow node
BasicBlock *StructurizeCFG::needPrefix(bool NeedEmpty) {
/// Create a new or reuse the previous node as flow node. Returns a block and a
/// debug location to be used for new instructions in that block.
std::pair<BasicBlock *, DebugLoc> StructurizeCFG::needPrefix(bool NeedEmpty) {
BasicBlock *Entry = PrevNode->getEntry();

if (!PrevNode->isSubRegion()) {
killTerminator(Entry);
DebugLoc DL = killTerminator(Entry);
if (!NeedEmpty || Entry->getFirstInsertionPt() == Entry->end())
return Entry;
return {Entry, DL};
}

// create a new flow node
Expand All @@ -1026,7 +1001,7 @@ BasicBlock *StructurizeCFG::needPrefix(bool NeedEmpty) {
// and wire it up
changeExit(PrevNode, Flow, true);
PrevNode = ParentRegion->getBBNode(Flow);
return Flow;
return {Flow, DebugLoc()};
}

/// Returns the region exit if possible, otherwise just a new flow node
Expand Down Expand Up @@ -1090,15 +1065,15 @@ void StructurizeCFG::wireFlow(bool ExitUseAllowed,
PrevNode = Node;
} else {
// Insert extra prefix node (or reuse last one)
BasicBlock *Flow = needPrefix(false);
auto [Flow, DL] = needPrefix(false);

// Insert extra postfix node (or use exit instead)
BasicBlock *Entry = Node->getEntry();
BasicBlock *Next = needPostfix(Flow, ExitUseAllowed);

// let it point to entry and next block
BranchInst *Br = BranchInst::Create(Entry, Next, BoolPoison, Flow);
setDebugLoc(Br, Flow);
Br->setDebugLoc(DL);
Conditions.push_back(Br);
addPhiValues(Flow, Entry);
DT->changeImmediateDominator(Entry, Flow);
Expand All @@ -1125,7 +1100,7 @@ void StructurizeCFG::handleLoops(bool ExitUseAllowed,
}

if (!isPredictableTrue(Node))
LoopStart = needPrefix(true);
LoopStart = needPrefix(true).first;

LoopEnd = Loops[Node->getEntry()];
wireFlow(false, LoopEnd);
Expand All @@ -1136,10 +1111,11 @@ void StructurizeCFG::handleLoops(bool ExitUseAllowed,
assert(LoopStart != &LoopStart->getParent()->getEntryBlock());

// Create an extra loop end node
LoopEnd = needPrefix(false);
DebugLoc DL;
std::tie(LoopEnd, DL) = needPrefix(false);
BasicBlock *Next = needPostfix(LoopEnd, ExitUseAllowed);
BranchInst *Br = BranchInst::Create(Next, LoopStart, BoolPoison, LoopEnd);
setDebugLoc(Br, LoopEnd);
Br->setDebugLoc(DL);
LoopConds.push_back(Br);
addPhiValues(LoopEnd, LoopStart);
setPrevNode(Next);
Expand Down Expand Up @@ -1339,7 +1315,6 @@ bool StructurizeCFG::run(Region *R, DominatorTree *DT) {
LoopPreds.clear();
LoopConds.clear();
FlowSet.clear();
TermDL.clear();

return true;
}
Expand Down
16 changes: 8 additions & 8 deletions llvm/test/CodeGen/AMDGPU/si-annotate-dbg-info.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -11,10 +11,10 @@ define amdgpu_ps i32 @if_else(i32 %0) !dbg !5 {
; OPT-NEXT: [[TMP4:%.*]] = extractvalue { i1, i64 } [[TMP2]], 1, !dbg [[DBG14]]
; OPT-NEXT: br i1 [[TMP3]], label [[FALSE:%.*]], label [[FLOW:%.*]], !dbg [[DBG14]]
; OPT: Flow:
; OPT-NEXT: [[TMP5:%.*]] = call { i1, i64 } @llvm.amdgcn.else.i64.i64(i64 [[TMP4]]), !dbg [[DBG14]]
; OPT-NEXT: [[TMP6:%.*]] = extractvalue { i1, i64 } [[TMP5]], 0, !dbg [[DBG14]]
; OPT-NEXT: [[TMP8:%.*]] = extractvalue { i1, i64 } [[TMP5]], 1, !dbg [[DBG14]]
; OPT-NEXT: br i1 [[TMP6]], label [[TRUE:%.*]], label [[EXIT:%.*]], !dbg [[DBG14]]
; OPT-NEXT: [[TMP5:%.*]] = call { i1, i64 } @llvm.amdgcn.else.i64.i64(i64 [[TMP4]])
; OPT-NEXT: [[TMP6:%.*]] = extractvalue { i1, i64 } [[TMP5]], 0
; OPT-NEXT: [[TMP8:%.*]] = extractvalue { i1, i64 } [[TMP5]], 1
; OPT-NEXT: br i1 [[TMP6]], label [[TRUE:%.*]], label [[EXIT:%.*]]
; OPT: true:
; OPT-NEXT: br label [[EXIT]], !dbg [[DBG15:![0-9]+]]
; OPT: false:
Expand Down Expand Up @@ -64,9 +64,9 @@ define amdgpu_ps void @loop_if_break(i32 %n) !dbg !19 {
; OPT-NEXT: [[TMP3]] = phi i32 [ [[I_NEXT]], [[LOOP_BODY]] ], [ poison, [[LOOP]] ]
; OPT-NEXT: [[TMP4:%.*]] = phi i1 [ false, [[LOOP_BODY]] ], [ true, [[LOOP]] ]
; OPT-NEXT: call void @llvm.amdgcn.end.cf.i64(i64 [[TMP2]])
; OPT-NEXT: [[TMP5]] = call i64 @llvm.amdgcn.if.break.i64(i1 [[TMP4]], i64 [[PHI_BROKEN]]), !dbg [[DBG27]]
; OPT-NEXT: [[TMP6:%.*]] = call i1 @llvm.amdgcn.loop.i64(i64 [[TMP5]]), !dbg [[DBG27]]
; OPT-NEXT: br i1 [[TMP6]], label [[EXIT:%.*]], label [[LOOP]], !dbg [[DBG27]]
; OPT-NEXT: [[TMP5]] = call i64 @llvm.amdgcn.if.break.i64(i1 [[TMP4]], i64 [[PHI_BROKEN]])
; OPT-NEXT: [[TMP6:%.*]] = call i1 @llvm.amdgcn.loop.i64(i64 [[TMP5]])
; OPT-NEXT: br i1 [[TMP6]], label [[EXIT:%.*]], label [[LOOP]]
; OPT: exit:
; OPT-NEXT: call void @llvm.amdgcn.end.cf.i64(i64 [[TMP5]])
; OPT-NEXT: ret void, !dbg [[DBG30:![0-9]+]]
Expand Down Expand Up @@ -132,7 +132,7 @@ attributes #0 = { nocallback nofree nosync nounwind speculatable willreturn memo
!30 = !DILocation(line: 13, column: 1, scope: !19)
;.
; OPT: [[META0:![0-9]+]] = distinct !DICompileUnit(language: DW_LANG_C, file: [[META1:![0-9]+]], producer: "debugify", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug)
; OPT: [[META1]] = !DIFile(filename: "../../../test/CodeGen/AMDGPU/si-annotate-dbg-info.ll", directory: {{.*}})
; OPT: [[META1]] = !DIFile(filename: "{{.*}}si-annotate-dbg-info.ll", directory: {{.*}})
; OPT: [[DBG5]] = distinct !DISubprogram(name: "if_else", linkageName: "if_else", scope: null, file: [[META1]], line: 1, type: [[META6:![0-9]+]], scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: [[META0]], retainedNodes: [[META8:![0-9]+]])
; OPT: [[META6]] = !DISubroutineType(types: [[META7:![0-9]+]])
; OPT: [[META7]] = !{}
Expand Down
16 changes: 8 additions & 8 deletions llvm/test/Transforms/StructurizeCFG/structurizecfg-debug-loc.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@ define void @if_then_else(ptr addrspace(1) %out, i1 %arg) !dbg !7 {
; CHECK: entry:
; CHECK: br i1 {{.*}}, label %if.else, label %Flow, !dbg [[ITE_ENTRY_DL:![0-9]+]]
; CHECK: Flow:
; CHECK: br i1 {{.*}}, label %if.then, label %exit, !dbg [[ITE_ENTRY_DL]]
; CHECK: br i1 {{.*}}, label %if.then, label %exit
; CHECK: if.then:
; CHECK: br label %exit, !dbg [[ITE_IFTHEN_DL:![0-9]+]]
; CHECK: if.else:
Expand Down Expand Up @@ -36,7 +36,7 @@ define void @while_loop(ptr addrspace(1) %out) !dbg !14 {
; CHECK: while.body:
; CHECK: br label %Flow, !dbg [[WHILE_BODY_DL:![0-9]+]]
; CHECK: Flow:
; CHECK: br i1 {{.*}}, label %exit, label %while.header, !dbg [[WHILE_HEADER_DL]]
; CHECK: br i1 {{.*}}, label %exit, label %while.header
; CHECK: exit:
;
entry:
Expand All @@ -63,7 +63,7 @@ define void @while_multiple_exits(ptr addrspace(1) %out) !dbg !21 {
; CHECK: while.exiting:
; CHECK: br label %Flow, !dbg [[WHILEME_EXITING_DL:![0-9]+]]
; CHECK: Flow:
; CHECK: br i1 {{.*}}, label %exit, label %while.header, !dbg [[WHILEME_HEADER_DL]]
; CHECK: br i1 {{.*}}, label %exit, label %while.header
; CHECK: exit:
;
entry:
Expand All @@ -86,27 +86,27 @@ define void @nested_if_then_else(ptr addrspace(1) %out, i1 %a, i1 %b) !dbg !28 {
; CHECK: entry:
; CHECK: br i1 {{.*}}, label %if.else, label %Flow4, !dbg [[NESTED_ENTRY_DL:![0-9]+]]
; CHECK: Flow4:
; CHECK: br i1 {{.*}}, label %if.then, label %exit, !dbg [[NESTED_ENTRY_DL]]
; CHECK: br i1 {{.*}}, label %if.then, label %exit
; CHECK: if.then:
; CHECK: br i1 {{.*}}, label %if.then.else, label %Flow2, !dbg [[NESTED_IFTHEN_DL:![0-9]+]]
; CHECK: Flow2:
; CHECK: br i1 {{.*}}, label %if.then.then, label %Flow3, !dbg [[NESTED_IFTHEN_DL]]
; CHECK: br i1 {{.*}}, label %if.then.then, label %Flow3
; CHECK: if.then.then:
; CHECK: br label %Flow3, !dbg [[NESTED_IFTHENTHEN_DL:![0-9]+]]
; CHECK: if.then.else:
; CHECK: br label %Flow2, !dbg [[NESTED_IFTHENELSE_DL:![0-9]+]]
; CHECK: if.else:
; CHECK: br i1 {{.*}}, label %if.else.else, label %Flow, !dbg [[NESTED_IFELSE_DL:![0-9]+]]
; CHECK: Flow:
; CHECK: br i1 {{.*}}, label %if.else.then, label %Flow1, !dbg [[NESTED_IFELSE_DL]]
; CHECK: br i1 {{.*}}, label %if.else.then, label %Flow1
; CHECK: if.else.then:
; CHECK: br label %Flow1, !dbg [[NESTED_IFELSETHEN_DL:![0-9]+]]
; CHECK: if.else.else:
; CHECK: br label %Flow, !dbg [[NESTED_IFELSEELSE_DL:![0-9]+]]
; CHECK: Flow1:
; CHECK: br label %Flow4, !dbg [[NESTED_IFELSE_DL]]
; CHECK: br label %Flow4
; CHECK: Flow3:
; CHECK: br label %exit, !dbg [[NESTED_IFTHEN_DL]]
; CHECK: br label %exit
; CHECK: exit:
;
entry:
Expand Down
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