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[DebugInfo] Avoid generating duplicate llvm.dbg.value
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Summary:
This is to avoid generating duplicate llvm.dbg.value instrinsic if it already exists after the Instruction.

Before inserting llvm.dbg.value instruction, LLVM checks if the same instruction is already present before the instruction to avoid duplicates.
Currently it misses to check if it already exists after the instruction.
flang generates IR like this.

%4 = load i32, i32* %i1_311, align 4, !dbg !42
call void @llvm.dbg.value(metadata i32 %4, metadata !35, metadata !DIExpression()), !dbg !33
When this IR is processed in llvm, it ends up inserting duplicates.
%4 = load i32, i32* %i1_311, align 4, !dbg !42
call void @llvm.dbg.value(metadata i32 %4, metadata !35, metadata !DIExpression()), !dbg !33
call void @llvm.dbg.value(metadata i32 %4, metadata !35, metadata !DIExpression()), !dbg !33
We have now updated LdStHasDebugValue to include the cases when instruction is already
followed by same dbg.value instruction we intend to insert.

Now,

Definition and usage of function LdStHasDebugValue are deleted.
RemoveRedundantDbgInstrs is called for the cleanup of duplicate dbg.value's

Testing:
Added unit test for validation
check-llvm
check-debuginfo (the debug info integration tests)

Reviewers: aprantl, probinson, dblaikie, jmorse, jini.susan.george
SouraVX, awpandey, dstenb, vsk

Reviewed By: aprantl, jmorse, dstenb, vsk

Differential Revision: https://reviews.llvm.org/D74030
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@alokkrsharma @SouraVX
alokkrsharma authored and SouraVX committed Mar 3, 2020
1 parent 57397eb commit 6f029da
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Showing 3 changed files with 201 additions and 27 deletions.
39 changes: 12 additions & 27 deletions llvm/lib/Transforms/Utils/Local.cpp
View file
Expand Up @@ -75,6 +75,7 @@
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/KnownBits.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/ValueMapper.h"
#include <algorithm>
#include <cassert>
Expand Down Expand Up @@ -1230,24 +1231,6 @@ unsigned llvm::getOrEnforceKnownAlignment(Value *V, unsigned PrefAlign,
/// Dbg Intrinsic utilities
///

/// See if there is a dbg.value intrinsic for DIVar before I.
static bool LdStHasDebugValue(DILocalVariable *DIVar, DIExpression *DIExpr,
Instruction *I) {
// Since we can't guarantee that the original dbg.declare instrinsic
// is removed by LowerDbgDeclare(), we need to make sure that we are
// not inserting the same dbg.value intrinsic over and over.
BasicBlock::InstListType::iterator PrevI(I);
if (PrevI != I->getParent()->getInstList().begin()) {
--PrevI;
if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(PrevI))
if (DVI->getValue() == I->getOperand(0) &&
DVI->getVariable() == DIVar &&
DVI->getExpression() == DIExpr)
return true;
}
return false;
}

/// See if there is a dbg.value intrinsic for DIVar for the PHI node.
static bool PhiHasDebugValue(DILocalVariable *DIVar,
DIExpression *DIExpr,
Expand Down Expand Up @@ -1324,13 +1307,11 @@ void llvm::ConvertDebugDeclareToDebugValue(DbgVariableIntrinsic *DII,
// know which part) we insert an dbg.value instrinsic to indicate that we
// know nothing about the variable's content.
DV = UndefValue::get(DV->getType());
if (!LdStHasDebugValue(DIVar, DIExpr, SI))
Builder.insertDbgValueIntrinsic(DV, DIVar, DIExpr, NewLoc, SI);
Builder.insertDbgValueIntrinsic(DV, DIVar, DIExpr, NewLoc, SI);
return;
}

if (!LdStHasDebugValue(DIVar, DIExpr, SI))
Builder.insertDbgValueIntrinsic(DV, DIVar, DIExpr, NewLoc, SI);
Builder.insertDbgValueIntrinsic(DV, DIVar, DIExpr, NewLoc, SI);
}

/// Inserts a llvm.dbg.value intrinsic before a load of an alloca'd value
Expand All @@ -1341,9 +1322,6 @@ void llvm::ConvertDebugDeclareToDebugValue(DbgVariableIntrinsic *DII,
auto *DIExpr = DII->getExpression();
assert(DIVar && "Missing variable");

if (LdStHasDebugValue(DIVar, DIExpr, LI))
return;

if (!valueCoversEntireFragment(LI->getType(), DII)) {
// FIXME: If only referring to a part of the variable described by the
// dbg.declare, then we want to insert a dbg.value for the corresponding
Expand Down Expand Up @@ -1410,6 +1388,7 @@ static bool isStructure(AllocaInst *AI) {
/// LowerDbgDeclare - Lowers llvm.dbg.declare intrinsics into appropriate set
/// of llvm.dbg.value intrinsics.
bool llvm::LowerDbgDeclare(Function &F) {
bool Changed = false;
DIBuilder DIB(*F.getParent(), /*AllowUnresolved*/ false);
SmallVector<DbgDeclareInst *, 4> Dbgs;
for (auto &FI : F)
Expand All @@ -1418,7 +1397,7 @@ bool llvm::LowerDbgDeclare(Function &F) {
Dbgs.push_back(DDI);

if (Dbgs.empty())
return false;
return Changed;

for (auto &I : Dbgs) {
DbgDeclareInst *DDI = I;
Expand Down Expand Up @@ -1471,8 +1450,14 @@ bool llvm::LowerDbgDeclare(Function &F) {
}
}
DDI->eraseFromParent();
Changed = true;
}
return true;

if (Changed)
for (BasicBlock &BB : F)
RemoveRedundantDbgInstrs(&BB);

return Changed;
}

/// Propagate dbg.value intrinsics through the newly inserted PHIs.
Expand Down
169 changes: 169 additions & 0 deletions llvm/test/DebugInfo/duplicate_dbgvalue.ll
View file
@@ -0,0 +1,169 @@
; RUN: opt -instcombine -S -o - < %s | FileCheck %s

; CHECK-LABEL: %4 = load i32, i32* %i1_311
; CHECK: call void @llvm.dbg.value(metadata i32 %4
; Next instruction should not be duplicate dbg.value intrinsic.
; CHECK-NEXT: @f90io_sc_i_ldw

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;program main
;integer :: res
; res = mfun()
; print *, res
;contains
; function mfun()
; integer :: i1
; i1 = 5
; mfun = fun(i1)
; write (*,*) i1
; end function
; function fun(a)
; integer, intent (in) :: a
; fun = a
; end function
;end program main
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

; ModuleID = 'duplicate_dbgvalue.ll'
source_filename = "duplicate_dbgvalue.ll"
target datalayout = "e-p:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

%struct.BSS1 = type <{ [4 x i8] }>

@.BSS1 = internal unnamed_addr global %struct.BSS1 zeroinitializer, align 32, !dbg !0
@.C303_MAIN_ = internal constant i32 6
@.C300_MAIN_ = internal constant [22 x i8] c"duplicate_dbgvalue.f90"
@.C302_MAIN_ = internal constant i32 4
@.C283_MAIN_ = internal constant i32 0
@.C283_main_mfun = internal constant i32 0
@.C302_main_mfun = internal constant i32 6
@.C300_main_mfun = internal constant [22 x i8] c"duplicate_dbgvalue.f90"
@.C313_main_mfun = internal constant i32 10

define void @MAIN_() local_unnamed_addr !dbg !2 {
L.entry:
call void (i8*, ...) bitcast (void (...)* @fort_init to void (i8*, ...)*)(i8* bitcast (i32* @.C283_MAIN_ to i8*)), !dbg !16
%0 = call fastcc i32 @main_mfun(), !dbg !18
store i32 %0, i32* bitcast (%struct.BSS1* @.BSS1 to i32*), align 32, !dbg !18
call void (i8*, i8*, i64, ...) bitcast (void (...)* @f90io_src_info03a to void (i8*, i8*, i64, ...)*)(i8* bitcast (i32* @.C302_MAIN_ to i8*), i8* getelementptr inbounds ([22 x i8], [22 x i8]* @.C300_MAIN_, i64 0, i64 0), i64 22), !dbg !23
%1 = call i32 (i8*, i8*, i8*, i8*, ...) bitcast (i32 (...)* @f90io_print_init to i32 (i8*, i8*, i8*, i8*, ...)*)(i8* bitcast (i32* @.C303_MAIN_ to i8*), i8* null, i8* bitcast (i32* @.C283_MAIN_ to i8*), i8* bitcast (i32* @.C283_MAIN_ to i8*)), !dbg !23
call void @llvm.dbg.value(metadata i32 %1, metadata !24, metadata !DIExpression()), !dbg !25
%2 = load i32, i32* bitcast (%struct.BSS1* @.BSS1 to i32*), align 32, !dbg !23
%3 = call i32 (i32, i32, ...) bitcast (i32 (...)* @f90io_sc_i_ldw to i32 (i32, i32, ...)*)(i32 %2, i32 25), !dbg !23
call void @llvm.dbg.value(metadata i32 %3, metadata !24, metadata !DIExpression()), !dbg !25
%4 = call i32 (...) @f90io_ldw_end(), !dbg !23
call void @llvm.dbg.value(metadata i32 %4, metadata !24, metadata !DIExpression()), !dbg !25
ret void, !dbg !26
}

define internal fastcc signext i32 @main_mfun() unnamed_addr !dbg !27 {
L.entry:
%i1_311 = alloca i32, align 4
call void @llvm.dbg.declare(metadata i64* undef, metadata !31, metadata !DIExpression()), !dbg !33
call void @llvm.dbg.declare(metadata i32* %i1_311, metadata !35, metadata !DIExpression()), !dbg !33
store i32 5, i32* %i1_311, align 4, !dbg !36
%0 = bitcast i32* %i1_311 to i64*, !dbg !41
%1 = call fastcc float @main_fun(i64* %0), !dbg !41
%2 = fptosi float %1 to i32, !dbg !41
call void (i8*, i8*, i64, ...) bitcast (void (...)* @f90io_src_info03a to void (i8*, i8*, i64, ...)*)(i8* bitcast (i32* @.C313_main_mfun to i8*), i8* getelementptr inbounds ([22 x i8], [22 x i8]* @.C300_main_mfun, i32 0, i32 0), i64 22), !dbg !42
%3 = call i32 (i8*, i8*, i8*, i8*, ...) bitcast (i32 (...)* @f90io_print_init to i32 (i8*, i8*, i8*, i8*, ...)*)(i8* bitcast (i32* @.C302_main_mfun to i8*), i8* null, i8* bitcast (i32* @.C283_main_mfun to i8*), i8* bitcast (i32* @.C283_main_mfun to i8*)), !dbg !42
call void @llvm.dbg.value(metadata i32 %3, metadata !43, metadata !DIExpression()), !dbg !33
%4 = load i32, i32* %i1_311, align 4, !dbg !42
call void @llvm.dbg.value(metadata i32 %4, metadata !35, metadata !DIExpression()), !dbg !33
%5 = call i32 (i32, i32, ...) bitcast (i32 (...)* @f90io_sc_i_ldw to i32 (i32, i32, ...)*)(i32 %4, i32 25), !dbg !42
call void @llvm.dbg.value(metadata i32 %5, metadata !43, metadata !DIExpression()), !dbg !33
%6 = call i32 (...) @f90io_ldw_end(), !dbg !42
call void @llvm.dbg.value(metadata i32 %6, metadata !43, metadata !DIExpression()), !dbg !33
ret i32 %2, !dbg !44
}

define internal fastcc float @main_fun(i64* noalias %a) unnamed_addr !dbg !45 {
L.entry:
call void @llvm.dbg.declare(metadata i64* %a, metadata !50, metadata !DIExpression()), !dbg !51
call void @llvm.dbg.declare(metadata i64* undef, metadata !53, metadata !DIExpression()), !dbg !51
%0 = bitcast i64* %a to i32*, !dbg !54
%1 = load i32, i32* %0, align 4, !dbg !54
%2 = sitofp i32 %1 to float, !dbg !54
ret float %2, !dbg !59
}

declare signext i32 @f90io_ldw_end(...) local_unnamed_addr

declare signext i32 @f90io_sc_i_ldw(...) local_unnamed_addr

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

declare signext i32 @f90io_print_init(...) local_unnamed_addr

declare void @f90io_src_info03a(...) local_unnamed_addr

declare void @fort_init(...) local_unnamed_addr

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

!llvm.module.flags = !{!14, !15}
!llvm.dbg.cu = !{!4}

!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
!1 = distinct !DIGlobalVariable(name: "res", scope: !2, file: !3, type: !9, isLocal: true, isDefinition: true)
!2 = distinct !DISubprogram(name: "main", scope: !4, file: !3, line: 1, type: !12, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagMainSubprogram, unit: !4)
!3 = !DIFile(filename: "duplicate-dbgvalue.f90", directory: "/dir")
!4 = distinct !DICompileUnit(language: DW_LANG_Fortran90, file: !3, producer: " F90 Flang - 1.5", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !5, retainedTypes: !5, globals: !6, imports: !5)
!5 = !{}
!6 = !{!0, !7, !10}
!7 = !DIGlobalVariableExpression(var: !8, expr: !DIExpression())
!8 = distinct !DIGlobalVariable(name: "res", scope: !4, file: !3, type: !9, isLocal: true, isDefinition: true)
!9 = !DIBasicType(name: "integer", size: 32, align: 32, encoding: DW_ATE_signed)
!10 = !DIGlobalVariableExpression(var: !11, expr: !DIExpression())
!11 = distinct !DIGlobalVariable(name: "res", scope: !4, file: !3, type: !9, isLocal: true, isDefinition: true)
!12 = !DISubroutineType(cc: DW_CC_program, types: !13)
!13 = !{null}
!14 = !{i32 2, !"Dwarf Version", i32 4}
!15 = !{i32 2, !"Debug Info Version", i32 3}
!16 = !DILocation(line: 1, column: 1, scope: !17)
!17 = !DILexicalBlock(scope: !2, file: !3, line: 1, column: 1)
!18 = !DILocation(line: 3, column: 1, scope: !17)
!19 = !{!20, !20, i64 0}
!20 = !{!"t1.2", !21, i64 0}
!21 = !{!"unlimited ptr", !22, i64 0}
!22 = !{!"Flang FAA 1"}
!23 = !DILocation(line: 4, column: 1, scope: !17)
!24 = !DILocalVariable(scope: !17, file: !3, type: !9, flags: DIFlagArtificial)
!25 = !DILocation(line: 0, scope: !17)
!26 = !DILocation(line: 5, column: 1, scope: !17)
!27 = distinct !DISubprogram(name: "mfun", scope: !2, file: !3, line: 6, type: !28, scopeLine: 6, spFlags: DISPFlagLocalToUnit | DISPFlagDefinition, unit: !4)
!28 = !DISubroutineType(types: !29)
!29 = !{!30}
!30 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !9, size: 64, align: 64)
!31 = !DILocalVariable(arg: 1, scope: !27, file: !3, type: !32, flags: DIFlagArtificial)
!32 = !DIBasicType(name: "uinteger*8", size: 64, align: 64, encoding: DW_ATE_unsigned)
!33 = !DILocation(line: 0, scope: !34)
!34 = !DILexicalBlock(scope: !27, file: !3, line: 6, column: 1)
!35 = !DILocalVariable(name: "i1", scope: !34, file: !3, type: !9)
!36 = !DILocation(line: 8, column: 1, scope: !34)
!37 = !{!38, !38, i64 0}
!38 = !{!"t2.2", !39, i64 0}
!39 = !{!"unlimited ptr", !40, i64 0}
!40 = !{!"Flang FAA 2"}
!41 = !DILocation(line: 9, column: 1, scope: !34)
!42 = !DILocation(line: 10, column: 1, scope: !34)
!43 = !DILocalVariable(scope: !34, file: !3, type: !9, flags: DIFlagArtificial)
!44 = !DILocation(line: 11, column: 1, scope: !34)
!45 = distinct !DISubprogram(name: "fun", scope: !2, file: !3, line: 12, type: !46, scopeLine: 12, spFlags: DISPFlagLocalToUnit | DISPFlagDefinition, unit: !4)
!46 = !DISubroutineType(types: !47)
!47 = !{!48, !9}
!48 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !49, size: 64, align: 64)
!49 = !DIBasicType(name: "real", size: 32, align: 32, encoding: DW_ATE_float)
!50 = !DILocalVariable(name: "a", arg: 1, scope: !45, file: !3, type: !9)
!51 = !DILocation(line: 0, scope: !52)
!52 = !DILexicalBlock(scope: !45, file: !3, line: 12, column: 1)
!53 = !DILocalVariable(arg: 2, scope: !45, file: !3, type: !32, flags: DIFlagArtificial)
!54 = !DILocation(line: 14, column: 1, scope: !52)
!55 = !{!56, !56, i64 0}
!56 = !{!"t3.2", !57, i64 0}
!57 = !{!"unlimited ptr", !58, i64 0}
!58 = !{!"Flang FAA 3"}
!59 = !DILocation(line: 15, column: 1, scope: !52)
20 changes: 20 additions & 0 deletions llvm/test/Transforms/Util/dbg-call-bitcast.ll
View file
Expand Up @@ -10,6 +10,26 @@ define dso_local void @_Z1fv() {
; CHECK: call void @_Z1gPv
call void @_Z1gPv(i8* nonnull %2)
%3 = bitcast i32* %1 to i8*
; CHECK-NOT: call void @llvm.dbg.value
; CHECK: call void @_Z1gPv
call void @_Z1gPv(i8* nonnull %3)
call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull %2)
ret void, !dbg !21
}

define dso_local void @_Z2fv() {
%1 = alloca i32, align 4
%2 = bitcast i32* %1 to i8*
call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull %2)
call void @llvm.dbg.declare(metadata i32* %1, metadata !16, metadata !DIExpression()), !dbg !19
; CHECK: %[[A:.*]] = alloca i32, align 4
; CHECK: call void @llvm.dbg.value(metadata i32* %[[A]], {{.*}}, metadata !DIExpression(DW_OP_deref)
; CHECK: call void @_Z1gPv
call void @_Z1gPv(i8* nonnull %2)
br label %block2

block2:
%3 = bitcast i32* %1 to i8*
; CHECK: call void @llvm.dbg.value(metadata i32* %[[A]], {{.*}}, metadata !DIExpression(DW_OP_deref)
; CHECK: call void @_Z1gPv
call void @_Z1gPv(i8* nonnull %3)
Expand Down

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