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[DebugInfo@O2][LoopVectorize] pr39024: Vectorized code linenos step t…
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…hrough loop even after completion

Summary:
Bug: https://bugs.llvm.org/show_bug.cgi?id=39024

The bug reports that a vectorized loop is stepped through 4 times and each step through the loop seemed to show a different path. I found two problems here:

A) An incorrect line number on a preheader block (for.body.preheader) instruction causes a step into the loop before it begins.
B) Instructions in the middle block have different line numbers which give the impression of another iteration.

In this patch I give all of the middle block instructions the line number of the scalar loop latch terminator branch. This seems to provide the smoothest debugging experience because the vectorized loops will always end on this line before dropping into the scalar loop. To solve problem A I have altered llvm::SplitBlockPredecessors to accommodate loop header blocks.

I have set up a separate review D61933 for a fix which is required for this patch.

Reviewers: samsonov, vsk, aprantl, probinson, anemet, hfinkel, jmorse

Reviewed By: hfinkel, jmorse

Subscribers: jmorse, javed.absar, eraman, kcc, bjope, jmellorcrummey, hfinkel, gbedwell, hiraditya, zzheng, llvm-commits

Tags: #llvm, #debug-info

Differential Revision: https://reviews.llvm.org/D60831

> llvm-svn: 363046

llvm-svn: 363786
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@OCHyams
OCHyams committed Jun 19, 2019
1 parent 45d19fb commit 1251cac
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Showing 14 changed files with 465 additions and 136 deletions.
8 changes: 7 additions & 1 deletion llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
View file
Expand Up @@ -579,7 +579,13 @@ BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB,

// The new block unconditionally branches to the old block.
BranchInst *BI = BranchInst::Create(BB, NewBB);
BI->setDebugLoc(BB->getFirstNonPHIOrDbg()->getDebugLoc());
// Splitting the predecessors of a loop header creates a preheader block.
if (LI && LI->isLoopHeader(BB))
// Using the loop start line number prevents debuggers stepping into the
// loop body for this instruction.
BI->setDebugLoc(LI->getLoopFor(BB)->getStartLoc());
else
BI->setDebugLoc(BB->getFirstNonPHIOrDbg()->getDebugLoc());

// Move the edges from Preds to point to NewBB instead of BB.
for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
Expand Down
20 changes: 14 additions & 6 deletions llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
View file
Expand Up @@ -2909,11 +2909,11 @@ BasicBlock *InnerLoopVectorizer::createVectorizedLoopSkeleton() {
CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_EQ, Count,
CountRoundDown, "cmp.n", MiddleBlock->getTerminator());

// Provide correct stepping behaviour by using the same DebugLoc as the
// scalar loop latch branch cmp if it exists.
if (CmpInst *ScalarLatchCmp =
dyn_cast_or_null<CmpInst>(ScalarLatchBr->getCondition()))
cast<Instruction>(CmpN)->setDebugLoc(ScalarLatchCmp->getDebugLoc());
// Here we use the same DebugLoc as the scalar loop latch branch instead
// of the corresponding compare because they may have ended up with
// different line numbers and we want to avoid awkward line stepping while
// debugging. Eg. if the compare has got a line number inside the loop.
cast<Instruction>(CmpN)->setDebugLoc(ScalarLatchBr->getDebugLoc());
}

BranchInst *BrInst = BranchInst::Create(ExitBlock, ScalarPH, CmpN);
Expand Down Expand Up @@ -3606,7 +3606,15 @@ void InnerLoopVectorizer::fixReduction(PHINode *Phi) {
// Reduce all of the unrolled parts into a single vector.
Value *ReducedPartRdx = VectorLoopValueMap.getVectorValue(LoopExitInst, 0);
unsigned Op = RecurrenceDescriptor::getRecurrenceBinOp(RK);
setDebugLocFromInst(Builder, ReducedPartRdx);

// The middle block terminator has already been assigned a DebugLoc here (the
// OrigLoop's single latch terminator). We want the whole middle block to
// appear to execute on this line because: (a) it is all compiler generated,
// (b) these instructions are always executed after evaluating the latch
// conditional branch, and (c) other passes may add new predecessors which
// terminate on this line. This is the easiest way to ensure we don't
// accidentally cause an extra step back into the loop while debugging.
setDebugLocFromInst(Builder, LoopMiddleBlock->getTerminator());
for (unsigned Part = 1; Part < UF; ++Part) {
Value *RdxPart = VectorLoopValueMap.getVectorValue(LoopExitInst, Part);
if (Op != Instruction::ICmp && Op != Instruction::FCmp)
Expand Down
149 changes: 76 additions & 73 deletions llvm/test/DebugInfo/AArch64/inlined-argument.ll
View file
Expand Up @@ -38,66 +38,59 @@
; if (__builtin_expect(enable, 0)) { }
; }


source_filename = "test.i"
; ModuleID = 'inlined-arg.c'
source_filename = "inlined-arg.c"
target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
target triple = "arm64-apple-ios5.0.0"

%struct.t = type { %struct.q* }
%struct.q = type { %struct.q*, i64 }

@tt = local_unnamed_addr global %struct.t* null, align 8, !dbg !0
@tt = common local_unnamed_addr global %struct.t* null, align 8, !dbg !0

; Function Attrs: noredzone nounwind readonly ssp
define i32 @g(%struct.t* nocapture readonly %t, i64 %r) local_unnamed_addr #0 !dbg !20 {
; Function Attrs: norecurse nounwind readonly ssp uwtable
define i32 @g(%struct.t* nocapture readonly %t, i64 %r) local_unnamed_addr !dbg !21 {
entry:
tail call void @llvm.dbg.value(metadata %struct.t* %t, metadata !26, metadata !DIExpression()), !dbg !29
tail call void @llvm.dbg.value(metadata i64 %r, metadata !27, metadata !DIExpression()), !dbg !30
tail call void @llvm.dbg.value(metadata %struct.t* %t, metadata !31, metadata !DIExpression()), !dbg !39
tail call void @llvm.dbg.value(metadata i64 %r, metadata !37, metadata !DIExpression()), !dbg !41
%s.i5 = bitcast %struct.t* %t to %struct.q**
tail call void @llvm.dbg.value(metadata %struct.q** %s.i5, metadata !38, metadata !DIExpression(DW_OP_deref)), !dbg !42
%q.06.i = load %struct.q*, %struct.q** %s.i5, align 8
tail call void @llvm.dbg.value(metadata %struct.q* %q.06.i, metadata !38, metadata !DIExpression()), !dbg !42
%tobool7.i = icmp eq %struct.q* %q.06.i, null, !dbg !43
br i1 %tobool7.i, label %find.exit, label %while.body.i.preheader, !dbg !43

while.body.i.preheader: ; preds = %entry
br label %while.body.i, !dbg !44
call void @llvm.dbg.value(metadata %struct.t* %t, metadata !27, metadata !DIExpression()), !dbg !30
call void @llvm.dbg.value(metadata i64 %r, metadata !28, metadata !DIExpression()), !dbg !31
call void @llvm.dbg.value(metadata %struct.t* %t, metadata !32, metadata !DIExpression()), !dbg !39
call void @llvm.dbg.value(metadata i64 %r, metadata !37, metadata !DIExpression()), !dbg !41
%s.i = getelementptr inbounds %struct.t, %struct.t* %t, i64 0, i32 0, !dbg !42
%q.05.i = load %struct.q*, %struct.q** %s.i, align 8, !dbg !43, !tbaa !44
call void @llvm.dbg.value(metadata %struct.q* %q.05.i, metadata !38, metadata !DIExpression()), !dbg !48
%tobool6.i = icmp eq %struct.q* %q.05.i, null, !dbg !49
br i1 %tobool6.i, label %find.exit, label %while.body.i, !dbg !49

while.body.i: ; preds = %while.body.i.preheader, %if.end.i
%q.08.i = phi %struct.q* [ %q.0.i, %if.end.i ], [ %q.06.i, %while.body.i.preheader ]
%resource1.i = getelementptr inbounds %struct.q, %struct.q* %q.08.i, i64 0, i32 1, !dbg !44
%0 = load i64, i64* %resource1.i, align 8, !dbg !44
%cmp.i = icmp eq i64 %0, %r, !dbg !47
br i1 %cmp.i, label %find.exit, label %if.end.i, !dbg !48
while.body.i: ; preds = %entry, %if.end.i
%q.07.i = phi %struct.q* [ %q.0.i, %if.end.i ], [ %q.05.i, %entry ]
%resource1.i = getelementptr inbounds %struct.q, %struct.q* %q.07.i, i64 0, i32 1, !dbg !50
%0 = load i64, i64* %resource1.i, align 8, !dbg !50, !tbaa !53
%cmp.i = icmp eq i64 %0, %r, !dbg !56
br i1 %cmp.i, label %find.exit, label %if.end.i, !dbg !57

if.end.i: ; preds = %while.body.i
%next.i6 = bitcast %struct.q* %q.08.i to %struct.q**
tail call void @llvm.dbg.value(metadata %struct.q** %next.i6, metadata !38, metadata !DIExpression(DW_OP_deref)), !dbg !42
%q.0.i = load %struct.q*, %struct.q** %next.i6, align 8
tail call void @llvm.dbg.value(metadata %struct.q* %q.0.i, metadata !38, metadata !DIExpression()), !dbg !42
%tobool.i = icmp eq %struct.q* %q.0.i, null, !dbg !43
br i1 %tobool.i, label %find.exit, label %while.body.i, !dbg !43, !llvm.loop !49
%next.i = getelementptr inbounds %struct.q, %struct.q* %q.07.i, i64 0, i32 0, !dbg !58
%q.0.i = load %struct.q*, %struct.q** %next.i, align 8, !dbg !43, !tbaa !44
call void @llvm.dbg.value(metadata %struct.q* %q.0.i, metadata !38, metadata !DIExpression()), !dbg !48
%tobool.i = icmp eq %struct.q* %q.0.i, null, !dbg !49
br i1 %tobool.i, label %find.exit, label %while.body.i, !dbg !49, !llvm.loop !59

find.exit: ; preds = %while.body.i, %if.end.i, %entry
ret i32 undef, !dbg !52
call void @llvm.dbg.value(metadata %struct.q* undef, metadata !29, metadata !DIExpression()), !dbg !61
ret i32 undef, !dbg !62
}

; Function Attrs: nounwind readnone speculatable
declare void @llvm.dbg.value(metadata, metadata, metadata) #1

attributes #0 = { noredzone nounwind readonly ssp }
attributes #1 = { nounwind readnone speculatable }
declare void @llvm.dbg.value(metadata, metadata, metadata)

!llvm.dbg.cu = !{!2}
!llvm.module.flags = !{!16, !17, !18}
!llvm.ident = !{!19}
!llvm.module.flags = !{!16, !17, !18, !19}
!llvm.ident = !{!20}

!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
!1 = distinct !DIGlobalVariable(name: "tt", scope: !2, file: !3, line: 8, type: !6, isLocal: false, isDefinition: true)
!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 6.0.0 (trunk 317516) (llvm/trunk 317518)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5)
!3 = !DIFile(filename: "test.i", directory: "/")
!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 9.0.0 (https://github.com/llvm/llvm-project.git cd3671d5dabc8848619d872f994770167a44ac5a)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5, nameTableKind: GNU)
!3 = !DIFile(filename: "inlined-arg.c", directory: "")
!4 = !{}
!5 = !{!0}
!6 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !7, size: 64)
Expand All @@ -113,37 +106,47 @@ attributes #1 = { nounwind readnone speculatable }
!16 = !{i32 2, !"Dwarf Version", i32 2}
!17 = !{i32 2, !"Debug Info Version", i32 3}
!18 = !{i32 1, !"wchar_size", i32 4}
!19 = !{!"clang version 6.0.0 (trunk 317516) (llvm/trunk 317518)"}
!20 = distinct !DISubprogram(name: "g", scope: !3, file: !3, line: 18, type: !21, isLocal: false, isDefinition: true, scopeLine: 18, flags: DIFlagPrototyped, isOptimized: true, unit: !2, retainedNodes: !25)
!21 = !DISubroutineType(types: !22)
!22 = !{!23, !24, !15}
!23 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!24 = !DIDerivedType(tag: DW_TAG_typedef, name: "t_t", file: !3, line: 1, baseType: !6)
!25 = !{!26, !27, !28}
!26 = !DILocalVariable(name: "t", arg: 1, scope: !20, file: !3, line: 18, type: !24)
!27 = !DILocalVariable(name: "r", arg: 2, scope: !20, file: !3, line: 18, type: !15)
!28 = !DILocalVariable(name: "q", scope: !20, file: !3, line: 19, type: !10)
!29 = !DILocation(line: 18, column: 11, scope: !20)
!30 = !DILocation(line: 18, column: 33, scope: !20)
!31 = !DILocalVariable(name: "t", arg: 1, scope: !32, file: !3, line: 9, type: !24)
!32 = distinct !DISubprogram(name: "find", scope: !3, file: !3, line: 9, type: !33, isLocal: true, isDefinition: true, scopeLine: 9, flags: DIFlagPrototyped, isOptimized: true, unit: !2, retainedNodes: !36)
!33 = !DISubroutineType(types: !34)
!34 = !{!35, !24, !15}
!35 = !DIBasicType(name: "long unsigned int", size: 64, encoding: DW_ATE_unsigned)
!36 = !{!31, !37, !38}
!37 = !DILocalVariable(name: "resource", arg: 2, scope: !32, file: !3, line: 9, type: !15)
!38 = !DILocalVariable(name: "q", scope: !32, file: !3, line: 10, type: !10)
!39 = !DILocation(line: 9, column: 31, scope: !32, inlinedAt: !40)
!40 = distinct !DILocation(line: 20, column: 7, scope: !20)
!41 = !DILocation(line: 9, column: 53, scope: !32, inlinedAt: !40)
!42 = !DILocation(line: 10, column: 13, scope: !32, inlinedAt: !40)
!43 = !DILocation(line: 12, column: 3, scope: !32, inlinedAt: !40)
!44 = !DILocation(line: 13, column: 12, scope: !45, inlinedAt: !40)
!45 = distinct !DILexicalBlock(scope: !46, file: !3, line: 13, column: 9)
!46 = distinct !DILexicalBlock(scope: !32, file: !3, line: 12, column: 13)
!47 = !DILocation(line: 13, column: 21, scope: !45, inlinedAt: !40)
!48 = !DILocation(line: 13, column: 9, scope: !46, inlinedAt: !40)
!49 = distinct !{!49, !50, !51}
!50 = !DILocation(line: 12, column: 3, scope: !32)
!51 = !DILocation(line: 16, column: 3, scope: !32)
!52 = !DILocation(line: 24, column: 1, scope: !20)
!19 = !{i32 7, !"PIC Level", i32 2}
!20 = !{!"clang version 9.0.0 (https://github.com/llvm/llvm-project.git cd3671d5dabc8848619d872f994770167a44ac5a)"}
!21 = distinct !DISubprogram(name: "g", scope: !3, file: !3, line: 19, type: !22, scopeLine: 19, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !26)
!22 = !DISubroutineType(types: !23)
!23 = !{!24, !25, !15}
!24 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!25 = !DIDerivedType(tag: DW_TAG_typedef, name: "t_t", file: !3, line: 1, baseType: !6)
!26 = !{!27, !28, !29}
!27 = !DILocalVariable(name: "t", arg: 1, scope: !21, file: !3, line: 19, type: !25)
!28 = !DILocalVariable(name: "r", arg: 2, scope: !21, file: !3, line: 19, type: !15)
!29 = !DILocalVariable(name: "q", scope: !21, file: !3, line: 20, type: !10)
!30 = !DILocation(line: 19, column: 11, scope: !21)
!31 = !DILocation(line: 19, column: 33, scope: !21)
!32 = !DILocalVariable(name: "t", arg: 1, scope: !33, file: !3, line: 10, type: !25)
!33 = distinct !DISubprogram(name: "find", scope: !3, file: !3, line: 10, type: !34, scopeLine: 10, flags: DIFlagPrototyped, spFlags: DISPFlagLocalToUnit | DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !36)
!34 = !DISubroutineType(types: !35)
!35 = !{!10, !25, !15}
!36 = !{!32, !37, !38}
!37 = !DILocalVariable(name: "resource", arg: 2, scope: !33, file: !3, line: 10, type: !15)
!38 = !DILocalVariable(name: "q", scope: !33, file: !3, line: 11, type: !10)
!39 = !DILocation(line: 10, column: 27, scope: !33, inlinedAt: !40)
!40 = distinct !DILocation(line: 21, column: 7, scope: !21)
!41 = !DILocation(line: 10, column: 49, scope: !33, inlinedAt: !40)
!42 = !DILocation(line: 12, column: 10, scope: !33, inlinedAt: !40)
!43 = !DILocation(line: 0, scope: !33, inlinedAt: !40)
!44 = !{!45, !45, i64 0}
!45 = !{!"any pointer", !46, i64 0}
!46 = !{!"omnipotent char", !47, i64 0}
!47 = !{!"Simple C/C++ TBAA"}
!48 = !DILocation(line: 11, column: 13, scope: !33, inlinedAt: !40)
!49 = !DILocation(line: 13, column: 3, scope: !33, inlinedAt: !40)
!50 = !DILocation(line: 14, column: 12, scope: !51, inlinedAt: !40)
!51 = distinct !DILexicalBlock(scope: !52, file: !3, line: 14, column: 9)
!52 = distinct !DILexicalBlock(scope: !33, file: !3, line: 13, column: 13)
!53 = !{!54, !55, i64 8}
!54 = !{!"q", !45, i64 0, !55, i64 8}
!55 = !{!"long long", !46, i64 0}
!56 = !DILocation(line: 14, column: 21, scope: !51, inlinedAt: !40)
!57 = !DILocation(line: 14, column: 9, scope: !52, inlinedAt: !40)
!58 = !DILocation(line: 16, column: 12, scope: !52, inlinedAt: !40)
!59 = distinct !{!59, !49, !60}
!60 = !DILocation(line: 17, column: 3, scope: !33, inlinedAt: !40)
!61 = !DILocation(line: 20, column: 13, scope: !21)
!62 = !DILocation(line: 24, column: 1, scope: !21)

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