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[indvars] Missing variables at Og:
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https://bugs.llvm.org/show_bug.cgi?id=51735
llvm#51077

In the given test case:

 4 ...
 5 void bar() {
 6   int End = 777;
 7   int Index = 27;
 8   char Var = 1;
 9   for (; Index < End; ++Index)
10     ;
11   nop(Index);
12 }
13 ...

Missing local variable 'Index' after loop 'Induction Variable Elimination'.
When adding a breakpoint at line 11, LLDB does not have information on
the variable. But it has info on 'Var' and 'End'.

- Moved the new logic to 'rewriteLoopExitValues'.
- Removed from the test cases, the unrelated functions: 'nop' and 'main'.
- Use 'isa<SCEVConstant>'.
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@CarlosAlbertoEnciso
CarlosAlbertoEnciso committed Mar 13, 2024
1 parent fdd13d9 commit a6260d4
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Showing 4 changed files with 30 additions and 77 deletions.
24 changes: 0 additions & 24 deletions llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1932,30 +1932,6 @@ bool IndVarSimplify::run(Loop *L) {
}
}

// The loop exit values have been updated; insert the debug location
// for the induction variable with its final value.
if (PHINode *IndVar = L->getInductionVariable(*SE)) {
const SCEV *IndVarSCEV = SE->getSCEVAtScope(IndVar, L->getParentLoop());
if (IndVarSCEV->getSCEVType() == SCEVTypes::scConstant) {
Value *FinalIVValue = cast<SCEVConstant>(IndVarSCEV)->getValue();
SmallVector<DbgVariableIntrinsic *> DbgUsers;
SmallVector<DbgVariableIntrinsic *> DbgUsersCloned;
findDbgUsers(DbgUsers, IndVar);
for (auto &DebugUser : DbgUsers) {
auto *Cloned = cast<DbgVariableIntrinsic>(DebugUser->clone());
Cloned->replaceVariableLocationOp(static_cast<unsigned>(0),
FinalIVValue);
DbgUsersCloned.push_back(Cloned);
}

SmallVector<BasicBlock *> ExitBlocks;
L->getExitBlocks(ExitBlocks);
for (BasicBlock *Exit : ExitBlocks)
for (auto &DebugUser : DbgUsersCloned)
DebugUser->insertBefore(Exit->getFirstNonPHI());
}
}

// Eliminate redundant IV cycles.
NumElimIV += Rewriter.replaceCongruentIVs(L, DT, DeadInsts, TTI);

Expand Down
26 changes: 26 additions & 0 deletions llvm/lib/Transforms/Utils/LoopUtils.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,7 @@
#include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/IR/DIBuilder.h"
#include "llvm/IR/DebugInfo.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
Expand Down Expand Up @@ -1619,6 +1620,31 @@ int llvm::rewriteLoopExitValues(Loop *L, LoopInfo *LI, TargetLibraryInfo *TLI,
// The insertion point instruction may have been deleted; clear it out
// so that the rewriter doesn't trip over it later.
Rewriter.clearInsertPoint();

// The loop exit values have been updated; insert the debug location
// for the induction variable with its final value.
if (PHINode *IndVar = L->getInductionVariable(*SE)) {
const SCEV *IndVarSCEV = SE->getSCEVAtScope(IndVar, L->getParentLoop());
if (isa<SCEVConstant>(IndVarSCEV)) {
Value *FinalIVValue = cast<SCEVConstant>(IndVarSCEV)->getValue();
SmallVector<DbgVariableIntrinsic *> DbgUsers;
SmallVector<DbgVariableIntrinsic *> DbgUsersCloned;
findDbgUsers(DbgUsers, IndVar);
for (auto &DebugUser : DbgUsers) {
auto *Cloned = cast<DbgVariableIntrinsic>(DebugUser->clone());
Cloned->replaceVariableLocationOp(static_cast<unsigned>(0),
FinalIVValue);
DbgUsersCloned.push_back(Cloned);
}

SmallVector<BasicBlock *> ExitBlocks;
L->getExitBlocks(ExitBlocks);
for (BasicBlock *Exit : ExitBlocks)
for (auto &DebugUser : DbgUsersCloned)
DebugUser->insertBefore(Exit->getFirstNonPHI());
}
}

return NumReplaced;
}

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34 changes: 3 additions & 31 deletions llvm/test/Transforms/LoopSimplify/pr51735-1.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -22,22 +22,12 @@
; 16 }

; CHECK: for.cond: {{.*}}
; CHECK: call void @llvm.dbg.value(metadata i32 poison, metadata ![[DBG:[0-9]+]], {{.*}}
; CHECK: call void @llvm.dbg.value(metadata i32 poison, metadata ![[DBG:[0-9]+]], {{.*}}
; CHECK: br i1 false, label %for.cond, label %for.end, {{.*}}
; CHECK: call void @llvm.dbg.value(metadata i32 %Index.{{[0-9]+}}, metadata ![[DBG:[0-9]+]], {{.*}}
; CHECK: call void @llvm.dbg.value(metadata i32 %inc, metadata ![[DBG:[0-9]+]], {{.*}}
; CHECK: for.end: {{.*}}
; CHECK: call void @llvm.dbg.value(metadata i32 777, metadata ![[DBG:[0-9]+]], {{.*}}
; CHECK: %call = tail call noundef i32 @_Z3nopi(i32 noundef 777), {{.*}}
; CHECK-DAG: ![[DBG]] = !DILocalVariable(name: "Index"{{.*}})

define dso_local noundef i32 @_Z3nopi(i32 noundef %Param) local_unnamed_addr #0 !dbg !10 {
entry:
%Param.addr = alloca i32, align 4
store i32 %Param, ptr %Param.addr, align 4
call void @llvm.dbg.declare(metadata ptr %Param.addr, metadata !15, metadata !DIExpression()), !dbg !16
ret i32 0, !dbg !17
}

define dso_local void @_Z3barv() local_unnamed_addr #2 !dbg !18 {
entry:
call void @llvm.dbg.value(metadata i32 777, metadata !21, metadata !DIExpression()), !dbg !22
Expand All @@ -55,24 +45,16 @@ for.cond: ; preds = %for.cond, %entry

for.end: ; preds = %for.cond
%Index.0.lcssa = phi i32 [ %Index.0, %for.cond ], !dbg !22
%call = tail call noundef i32 @_Z3nopi(i32 noundef %Index.0.lcssa), !dbg !34
ret void, !dbg !35
}

define dso_local noundef i32 @main() local_unnamed_addr #3 !dbg !36 {
entry:
call void @_Z3barv(), !dbg !39
ret i32 0, !dbg !40
}

declare void @llvm.dbg.value(metadata, metadata, metadata)
declare void @llvm.dbg.declare(metadata, metadata, metadata)

!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!2, !3, !4, !5, !6, !7, !8}
!llvm.ident = !{!9}

!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 18.0.0 (https://github.com/llvm/llvm-project.git 18c2eb2bf02bd7666523aa566e45d62053b7db80)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
!1 = !DIFile(filename: "test.cpp", directory: "")
!2 = !{i32 7, !"Dwarf Version", i32 5}
!3 = !{i32 2, !"Debug Info Version", i32 3}
Expand All @@ -82,14 +64,9 @@ declare void @llvm.dbg.declare(metadata, metadata, metadata)
!7 = !{i32 7, !"uwtable", i32 2}
!8 = !{i32 7, !"frame-pointer", i32 2}
!9 = !{!"clang version 18.0.0"}
!10 = distinct !DISubprogram(name: "nop", linkageName: "_Z3nopi", scope: !1, file: !1, line: 1, type: !11, scopeLine: 1, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !14)
!11 = !DISubroutineType(types: !12)
!12 = !{!13, !13}
!13 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!14 = !{}
!15 = !DILocalVariable(name: "Param", arg: 1, scope: !10, file: !1, line: 1, type: !13)
!16 = !DILocation(line: 1, column: 38, scope: !10)
!17 = !DILocation(line: 2, column: 3, scope: !10)
!18 = distinct !DISubprogram(name: "bar", linkageName: "_Z3barv", scope: !1, file: !1, line: 5, type: !19, scopeLine: 5, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !14)
!19 = !DISubroutineType(types: !20)
!20 = !{null}
Expand All @@ -108,8 +85,3 @@ declare void @llvm.dbg.declare(metadata, metadata, metadata)
!33 = !{!"llvm.loop.mustprogress"}
!34 = !DILocation(line: 11, column: 3, scope: !18)
!35 = !DILocation(line: 12, column: 1, scope: !18)
!36 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 14, type: !37, scopeLine: 14, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0)
!37 = !DISubroutineType(types: !38)
!38 = !{!13}
!39 = !DILocation(line: 15, column: 3, scope: !36)
!40 = !DILocation(line: 16, column: 1, scope: !36)
23 changes: 1 addition & 22 deletions llvm/test/Transforms/LoopSimplify/pr51735.ll
View file
Original file line number Diff line number Diff line change
Expand Up @@ -27,14 +27,8 @@
; CHECK: br i1 false, label %for.cond, label %for.end, {{.*}}
; CHECK: for.end: {{.*}}
; CHECK: call void @llvm.dbg.value(metadata i32 777, metadata ![[DBG:[0-9]+]], {{.*}}
; CHECK: %call = tail call noundef i32 @_Z3nopv(), {{.*}}
; CHECK-DAG: ![[DBG]] = !DILocalVariable(name: "Index"{{.*}})

define dso_local noundef i32 @_Z3nopv() local_unnamed_addr #0 !dbg !10 {
entry:
ret i32 0, !dbg !14
}

define dso_local void @_Z3barv() local_unnamed_addr #1 !dbg !15 {
entry:
call void @llvm.dbg.value(metadata i32 777, metadata !19, metadata !DIExpression()), !dbg !20
Expand All @@ -51,23 +45,16 @@ for.cond: ; preds = %for.cond, %entry
br i1 %cmp, label %for.cond, label %for.end, !dbg !28, !llvm.loop !29

for.end: ; preds = %for.cond
%call = tail call noundef i32 @_Z3nopv(), !dbg !32
ret void, !dbg !33
}

define dso_local noundef i32 @main() local_unnamed_addr #2 !dbg !34 {
entry:
call void @_Z3barv(), !dbg !35
ret i32 0, !dbg !36
}

declare void @llvm.dbg.value(metadata, metadata, metadata)

!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!2, !3, !4, !5, !6, !7, !8}
!llvm.ident = !{!9}

!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 18.0.0 (https://github.com/llvm/llvm-project.git 18c2eb2bf02bd7666523aa566e45d62053b7db80)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
!1 = !DIFile(filename: "test.cpp", directory: "")
!2 = !{i32 7, !"Dwarf Version", i32 5}
!3 = !{i32 2, !"Debug Info Version", i32 3}
Expand All @@ -77,11 +64,7 @@ declare void @llvm.dbg.value(metadata, metadata, metadata)
!7 = !{i32 7, !"uwtable", i32 2}
!8 = !{i32 7, !"frame-pointer", i32 2}
!9 = !{!"clang version 18.0.0"}
!10 = distinct !DISubprogram(name: "nop", linkageName: "_Z3nopv", scope: !1, file: !1, line: 1, type: !11, scopeLine: 1, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0)
!11 = !DISubroutineType(types: !12)
!12 = !{!13}
!13 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!14 = !DILocation(line: 2, column: 3, scope: !10)
!15 = distinct !DISubprogram(name: "bar", linkageName: "_Z3barv", scope: !1, file: !1, line: 5, type: !16, scopeLine: 5, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !18)
!16 = !DISubroutineType(types: !17)
!17 = !{null}
Expand All @@ -99,8 +82,4 @@ declare void @llvm.dbg.value(metadata, metadata, metadata)
!29 = distinct !{!29, !28, !30, !31}
!30 = !DILocation(line: 10, column: 5, scope: !26)
!31 = !{!"llvm.loop.mustprogress"}
!32 = !DILocation(line: 11, column: 3, scope: !15)
!33 = !DILocation(line: 12, column: 1, scope: !15)
!34 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 14, type: !11, scopeLine: 14, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0)
!35 = !DILocation(line: 15, column: 3, scope: !34)
!36 = !DILocation(line: 16, column: 1, scope: !34)

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