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[DebugInfo][DAG] Don't reuse debug location on COPY if width changes. 

Summary:
This caused incorrect debug information for parameters:
Previously, after a COPY of a parameter that changes the width,
we would emit a DBG_VALUE that continues to be associated to that
parameter, even though it now used a different width.
This made the LiveDebugValues pass assume the parameter value
got clobbered and it stopped tracking the parameter entry
value, leading to incorrect debug information.

Fixes https://bugs.llvm.org/show_bug.cgi?id=39715

Subscribers: aprantl, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D80819
This commit is contained in:
Tobias Bosch 2020-05-28 15:40:43 -07:00
parent f66a43c11a
commit 6a4714030e
2 changed files with 61 additions and 1 deletions
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4
llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
View File

@ -623,7 +623,9 @@ bool SelectionDAGISel::runOnMachineFunction(MachineFunction &mf) {
// Otherwise this is another use or second copy use.
CopyUseMI = nullptr; break;
}
if (CopyUseMI) {
if (CopyUseMI &&
TRI.getRegSizeInBits(LDI->second, MRI) ==
TRI.getRegSizeInBits(CopyUseMI->getOperand(0).getReg(), MRI)) {
// Use MI's debug location, which describes where Variable was
// declared, rather than whatever is attached to CopyUseMI.
MachineInstr *NewMI =

58
llvm/test/DebugInfo/X86/dbg-value-funcarg3.ll Normal file
View File

@ -0,0 +1,58 @@
; RUN: llc -mtriple=x86_64-unknown-linux-gnu -start-after=codegenprepare -stop-before=finalize-isel -o - %s | FileCheck %s
; Input to this test looked like this and was compiled using: clang -g -O1 -mllvm -stop-after=codegenprepare -S
;
; int fn1(long t1) {
; return t;
; }
;
; Catch metadata references for involved variables.
;
; CHECK-DAG: ![[T1:.*]] = !DILocalVariable(name: "t1"
define dso_local i32 @fn1(i64 %t1) local_unnamed_addr #0 !dbg !7 {
; We expect that the same width COPY reuses the debug location,
; but the width narrowing COPY does not.
;
; CHECK-LABEL: name: fn1
; CHECK: DBG_VALUE $rdi, $noreg, ![[T1]], !DIExpression(),
; CHECK-NEXT: %0:gr64 = COPY $rdi
; CHECK-NEXT: DBG_VALUE %0, $noreg, ![[T1]], !DIExpression(),
; CHECK-NEXT: %1:gr32 = COPY %0.sub_32bit
; CHECK-NEXT: COPY
; CHECK-NEXT: RET
entry:
call void @llvm.dbg.value(metadata i64 %t1, metadata !13, metadata !DIExpression()), !dbg !14
%0 = trunc i64 %t1 to i32, !dbg !15
ret i32 %0, !dbg !16
}
declare void @llvm.dbg.value(metadata, metadata, metadata) #1
attributes #0 = { norecurse nounwind readnone uwtable }
attributes #1 = { nounwind readnone speculatable willreturn }
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!3, !4, !5}
!llvm.ident = !{!6}
!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 11.0.0 (git@github.com:tbosch/llvm-project.git 0b11aed869bf09ba60
d7ed17334cf0b76e6a5922)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, splitDebugInlining: false, nameTableKind: None)
!1 = !DIFile(filename: "test.cc", directory: "")
!2 = !{}
!3 = !{i32 7, !"Dwarf Version", i32 4}
!4 = !{i32 2, !"Debug Info Version", i32 3}
!5 = !{i32 1, !"wchar_size", i32 4}
!6 = !{!"clang version 11.0.0 (git@github.com:tbosch/llvm-project.git 0b11aed869bf09ba60d7ed17334cf0b76e6a5922)"}
!7 = distinct !DISubprogram(name: "fn1", scope: !1, file: !1, line: 1, type: !8, scopeLine: 1, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !12)
!8 = !DISubroutineType(types: !9)
!9 = !{!10, !11}
!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!11 = !DIBasicType(name: "long int", size: 64, encoding: DW_ATE_signed)
!12 = !{!13}
!13 = !DILocalVariable(name: "t1", arg: 1, scope: !7, file: !1, line: 1, type: !11)
!14 = !DILocation(line: 0, scope: !7)
!15 = !DILocation(line: 2, column: 10, scope: !7)
!16 = !DILocation(line: 2, column: 3, scope: !7)