[llvm] [DebugInfo] Don't set prologue_end behind line-zero call insts (PR #156850)
Jeremy Morse via llvm-commits
llvm-commits at lists.llvm.org
Mon Nov 17 05:37:50 PST 2025
https://github.com/jmorse updated https://github.com/llvm/llvm-project/pull/156850
>From 805558861e45e78a0fda96229a2458dd59bea435 Mon Sep 17 00:00:00 2001
From: Jeremy Morse <jeremy.morse at sony.com>
Date: Thu, 4 Sep 2025 11:31:11 +0100
Subject: [PATCH 1/4] [DebugInfo] Don't set prologue_end behind line-zero call
insts
In functions that have been seriously deformed during optimisation, there
can be call instructions with line-zero immediately after frame setup (see
C reproducer in the test added). Our previous algorithms for prologue_end
ignored these, meaning someone entering a function at prologue_end would
break-in after a function call had completed. Prefer instead to not emit
prologue_end at all: there is no good place to put it.
---
llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp | 9 ++
llvm/test/DebugInfo/MIR/X86/debug-loc-0.mir | 2 +-
.../X86/no-prologue-end-after-line0-calls.mir | 129 ++++++++++++++++++
3 files changed, 139 insertions(+), 1 deletion(-)
create mode 100644 llvm/test/DebugInfo/X86/no-prologue-end-after-line0-calls.mir
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 30db817ba3144..42b525f2dd6f7 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -2305,6 +2305,15 @@ findPrologueEndLoc(const MachineFunction *MF) {
return *FoundInst;
}
+ // We choose to ignore line-zero locations when setting the prologue as they
+ // can't be stepped on anyway; however in very rare scenarios function calls
+ // can have line zero, and we shouldn't step over those. In these
+ // extraordinary conditions, just bail out and refuse to set a prologue_end.
+ if (CurInst->isCall())
+ if (const DILocation *Loc = CurInst->getDebugLoc().get())
+ if (Loc->getLine() == 0)
+ return std::make_pair(nullptr, true);
+
// Try to continue searching, but use a backup-location if substantive
// computation is happening.
auto NextInst = std::next(CurInst);
diff --git a/llvm/test/DebugInfo/MIR/X86/debug-loc-0.mir b/llvm/test/DebugInfo/MIR/X86/debug-loc-0.mir
index 01862f5905f9c..71489d5a5e485 100644
--- a/llvm/test/DebugInfo/MIR/X86/debug-loc-0.mir
+++ b/llvm/test/DebugInfo/MIR/X86/debug-loc-0.mir
@@ -5,7 +5,7 @@
# CHECK: Ltmp0:
# CHECK: .loc 1 0 0
# CHECK-NOT: .loc 1 0 0
-# CHECK: .loc 1 37 1 prologue_end
+# CHECK: .loc 1 37 1
--- |
; ModuleID = '<stdin>'
diff --git a/llvm/test/DebugInfo/X86/no-prologue-end-after-line0-calls.mir b/llvm/test/DebugInfo/X86/no-prologue-end-after-line0-calls.mir
new file mode 100644
index 0000000000000..604b9d1d2eafb
--- /dev/null
+++ b/llvm/test/DebugInfo/X86/no-prologue-end-after-line0-calls.mir
@@ -0,0 +1,129 @@
+# RUN: llc %s -start-after=livedebugvalues -o - -filetype=obj | llvm-dwarfdump - --debug-line | FileCheck %s --implicit-check-not=prologue_end
+#
+## Original code, compiled clang -O2 -g -c
+##
+## void ext();
+## int main(int argc, char **argv) {
+## if (argc == 1)
+## ext();
+## else
+## ext();
+## return 0;
+## }
+##
+## In the code sequence above, the call to ext is given line zero during
+## optimisation, because the code is duplicated down all function paths thus
+## gets merged. We get something like this as the output:
+##
+## 0: 50 push %rax
+## 1: 31 c0 xor %eax,%eax
+## 3: e8 00 00 00 00 call 8 <main+0x8>
+## 4: R_X86_64_PLT32 ext-0x4
+## 8: 31 c0 xor %eax,%eax
+## a: 59 pop %rcx
+## b: c3 ret
+##
+## Where prologue_end is placed on address 8, the clearing of the return
+## register, because it's the first "real" instruction that isn't line zero.
+## This then causes debuggers to skip over the call instruction when entering
+## the function, which is catastrophic.
+##
+## Instead: we shouldn't put a prologue_end on this function at all. It's too
+## deformed from the original code to truly have a position (with a line number)
+## that is both true, and after frame setup. This gives comsumers the
+## opportunity to recognise "this is a crazy function" and act accordingly.
+##
+## Check lines ensure that there's something meaningful in the line table
+## involving line 2, the implicit-check-not is making sure there isn't a
+## prologue_end flag on any line entry.
+#
+# CHECK: standard_opcode_lengths[DW_LNS_set_prologue_end] = 0
+#
+# CHECK: Address Line Column File
+# CHECK: 2 0 0
+# CHECK: end_sequence
+--- |
+ ; ModuleID = '/tmp/test.c'
+ source_filename = "/tmp/test.c"
+ target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+ target triple = "x86_64-unknown-linux-gnu"
+
+ ; Function Attrs: nounwind uwtable
+ define dso_local noundef i32 @main(i32 noundef %argc, ptr noundef readnone captures(none) %argv) local_unnamed_addr !dbg !10 {
+ entry:
+ #dbg_value(i32 %argc, !19, !DIExpression(), !21)
+ #dbg_value(ptr %argv, !20, !DIExpression(), !21)
+ tail call void (...) @ext(), !dbg !22
+ ret i32 0, !dbg !24
+ }
+
+ declare !dbg !25 void @ext(...) local_unnamed_addr
+
+ !llvm.dbg.cu = !{!0}
+ !llvm.module.flags = !{!2, !3, !4, !5, !6, !7, !8}
+ !llvm.ident = !{!9}
+
+ !0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang version 22.0.0git (/fast/fs/llvm4 8989ec5439dc2df2aeb7e5ea3e6c255ce8e9634d)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+ !1 = !DIFile(filename: "/tmp/test.c", directory: "/fast/fs/llvm-stage/debug", checksumkind: CSK_MD5, checksum: "9862df54ae1fdd9354308eae69de364a")
+ !2 = !{i32 7, !"Dwarf Version", i32 5}
+ !3 = !{i32 2, !"Debug Info Version", i32 3}
+ !4 = !{i32 1, !"wchar_size", i32 4}
+ !5 = !{i32 8, !"PIC Level", i32 2}
+ !6 = !{i32 7, !"PIE Level", i32 2}
+ !7 = !{i32 7, !"uwtable", i32 2}
+ !8 = !{i32 7, !"debug-info-assignment-tracking", i1 true}
+ !9 = !{!"clang version 22.0.0git (/fast/fs/llvm4 8989ec5439dc2df2aeb7e5ea3e6c255ce8e9634d)"}
+ !10 = distinct !DISubprogram(name: "main", scope: !11, file: !11, line: 2, type: !12, scopeLine: 2, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !18, keyInstructions: true)
+ !11 = !DIFile(filename: "/tmp/test.c", directory: "", checksumkind: CSK_MD5, checksum: "9862df54ae1fdd9354308eae69de364a")
+ !12 = !DISubroutineType(types: !13)
+ !13 = !{!14, !14, !15}
+ !14 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+ !15 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !16, size: 64)
+ !16 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !17, size: 64)
+ !17 = !DIBasicType(name: "char", size: 8, encoding: DW_ATE_signed_char)
+ !18 = !{!19, !20}
+ !19 = !DILocalVariable(name: "argc", arg: 1, scope: !10, file: !11, line: 2, type: !14)
+ !20 = !DILocalVariable(name: "argv", arg: 2, scope: !10, file: !11, line: 2, type: !15)
+ !21 = !DILocation(line: 0, scope: !10)
+ !22 = !DILocation(line: 0, scope: !23)
+ !23 = distinct !DILexicalBlock(scope: !10, file: !11, line: 3, column: 7)
+ !24 = !DILocation(line: 7, column: 4, scope: !10, atomGroup: 2, atomRank: 1)
+ !25 = !DISubprogram(name: "ext", scope: !11, file: !11, line: 1, type: !26, spFlags: DISPFlagOptimized)
+ !26 = !DISubroutineType(types: !27)
+ !27 = !{null}
+...
+---
+name: main
+alignment: 16
+tracksRegLiveness: true
+noPhis: true
+isSSA: false
+noVRegs: true
+hasFakeUses: false
+debugInstrRef: true
+tracksDebugUserValues: true
+frameInfo:
+ stackSize: 8
+ offsetAdjustment: -8
+ maxAlignment: 1
+ adjustsStack: true
+ hasCalls: true
+ maxCallFrameSize: 0
+ isCalleeSavedInfoValid: true
+machineFunctionInfo:
+ amxProgModel: None
+body: |
+ bb.0.entry:
+ DBG_VALUE $edi, $noreg, !19, !DIExpression(), debug-location !21
+ DBG_VALUE $rsi, $noreg, !20, !DIExpression(), debug-location !21
+ frame-setup PUSH64r undef $rax, implicit-def $rsp, implicit $rsp
+ frame-setup CFI_INSTRUCTION def_cfa_offset 16
+ dead $eax = XOR32rr undef $eax, undef $eax, implicit-def dead $eflags, implicit-def $al, debug-location !22
+ CALL64pcrel32 target-flags(x86-plt) @ext, csr_64, implicit $rsp, implicit $ssp, implicit killed $al, implicit-def $rsp, implicit-def $ssp, debug-location !22
+ DBG_VALUE $rsi, $noreg, !20, !DIExpression(DW_OP_LLVM_entry_value, 1), debug-location !21
+ DBG_VALUE $edi, $noreg, !19, !DIExpression(DW_OP_LLVM_entry_value, 1), debug-location !21
+ $eax = XOR32rr undef $eax, undef $eax, implicit-def dead $eflags, debug-location !24
+ $rcx = frame-destroy POP64r implicit-def $rsp, implicit $rsp, debug-location !24
+ frame-destroy CFI_INSTRUCTION def_cfa_offset 8, debug-location !24
+ RET64 $eax, debug-location !24
+...
>From 30a0c4e1f25271c71d5671521b702d8022a0c530 Mon Sep 17 00:00:00 2001
From: Jeremy Morse <jeremy.morse at sony.com>
Date: Thu, 11 Sep 2025 16:27:24 +0100
Subject: [PATCH 2/4] Spelling, strings, spacing
---
.../X86/no-prologue-end-after-line0-calls.mir | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)
diff --git a/llvm/test/DebugInfo/X86/no-prologue-end-after-line0-calls.mir b/llvm/test/DebugInfo/X86/no-prologue-end-after-line0-calls.mir
index 604b9d1d2eafb..b3efc0321c2af 100644
--- a/llvm/test/DebugInfo/X86/no-prologue-end-after-line0-calls.mir
+++ b/llvm/test/DebugInfo/X86/no-prologue-end-after-line0-calls.mir
@@ -18,7 +18,7 @@
## 0: 50 push %rax
## 1: 31 c0 xor %eax,%eax
## 3: e8 00 00 00 00 call 8 <main+0x8>
-## 4: R_X86_64_PLT32 ext-0x4
+## 4: R_X86_64_PLT32 ext-0x4
## 8: 31 c0 xor %eax,%eax
## a: 59 pop %rcx
## b: c3 ret
@@ -30,7 +30,7 @@
##
## Instead: we shouldn't put a prologue_end on this function at all. It's too
## deformed from the original code to truly have a position (with a line number)
-## that is both true, and after frame setup. This gives comsumers the
+## that is both true, and after frame setup. This gives consumers the
## opportunity to recognise "this is a crazy function" and act accordingly.
##
## Check lines ensure that there's something meaningful in the line table
@@ -43,8 +43,6 @@
# CHECK: 2 0 0
# CHECK: end_sequence
--- |
- ; ModuleID = '/tmp/test.c'
- source_filename = "/tmp/test.c"
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
@@ -63,8 +61,8 @@
!llvm.module.flags = !{!2, !3, !4, !5, !6, !7, !8}
!llvm.ident = !{!9}
- !0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang version 22.0.0git (/fast/fs/llvm4 8989ec5439dc2df2aeb7e5ea3e6c255ce8e9634d)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
- !1 = !DIFile(filename: "/tmp/test.c", directory: "/fast/fs/llvm-stage/debug", checksumkind: CSK_MD5, checksum: "9862df54ae1fdd9354308eae69de364a")
+ !0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+ !1 = !DIFile(filename: "/tmp/test.c", directory: "")
!2 = !{i32 7, !"Dwarf Version", i32 5}
!3 = !{i32 2, !"Debug Info Version", i32 3}
!4 = !{i32 1, !"wchar_size", i32 4}
@@ -72,9 +70,9 @@
!6 = !{i32 7, !"PIE Level", i32 2}
!7 = !{i32 7, !"uwtable", i32 2}
!8 = !{i32 7, !"debug-info-assignment-tracking", i1 true}
- !9 = !{!"clang version 22.0.0git (/fast/fs/llvm4 8989ec5439dc2df2aeb7e5ea3e6c255ce8e9634d)"}
+ !9 = !{!"clang"}
!10 = distinct !DISubprogram(name: "main", scope: !11, file: !11, line: 2, type: !12, scopeLine: 2, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !18, keyInstructions: true)
- !11 = !DIFile(filename: "/tmp/test.c", directory: "", checksumkind: CSK_MD5, checksum: "9862df54ae1fdd9354308eae69de364a")
+ !11 = !DIFile(filename: "/tmp/test.c", directory: "")
!12 = !DISubroutineType(types: !13)
!13 = !{!14, !14, !15}
!14 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
>From fe4f6355d6528ebc88158f1e4c5e0fb2e3fcca9c Mon Sep 17 00:00:00 2001
From: Jeremy Morse <jeremy.morse at sony.com>
Date: Fri, 14 Nov 2025 09:02:24 +0000
Subject: [PATCH 3/4] Revise prologue-end setting as per Davids feedback
---
llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp | 36 +++++++++++++++----
.../X86/no-prologue-end-after-line0-calls.mir | 32 ++++++++---------
2 files changed, 45 insertions(+), 23 deletions(-)
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 42b525f2dd6f7..a8904a46dd571 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -2218,6 +2218,7 @@ findPrologueEndLoc(const MachineFunction *MF) {
const auto &TII = *MF->getSubtarget().getInstrInfo();
const MachineInstr *NonTrivialInst = nullptr;
const Function &F = MF->getFunction();
+ DISubprogram *SP = const_cast<DISubprogram*>(F.getSubprogram());
// Some instructions may be inserted into prologue after this function. Must
// keep prologue for these cases.
@@ -2305,15 +2306,36 @@ findPrologueEndLoc(const MachineFunction *MF) {
return *FoundInst;
}
- // We choose to ignore line-zero locations when setting the prologue as they
- // can't be stepped on anyway; however in very rare scenarios function calls
- // can have line zero, and we shouldn't step over those. In these
- // extraordinary conditions, just bail out and refuse to set a prologue_end.
- if (CurInst->isCall())
- if (const DILocation *Loc = CurInst->getDebugLoc().get())
- if (Loc->getLine() == 0)
+ // In very rare scenarios function calls can have line zero, and we
+ // shouldn't step over such a call while trying to reach prologue_end. In
+ // these extraordinary conditions, force an earlier setup instruction to
+ // have the scope line and put prologue_end there. This will be suboptimal,
+ // and might still be in setup code, but is less catastrophic than missing
+ // a call.
+ if (CurInst->isCall()) {
+ if (const DILocation *Loc = CurInst->getDebugLoc().get();
+ Loc && Loc->getLine() == 0) {
+ // Go back one instruction.
+ auto RIt = std::next(CurInst->getIterator().getReverse());
+ // In the radically unlikely event that there's no prior instruction,
+ // meaning the first instruction in the function is a call, don't set a
+ // prologue_end at all.
+ if (RIt == CurInst->getParent()->rend())
return std::make_pair(nullptr, true);
+ // The prior instruction was either line-zero or unset, or a setup
+ // instruction, or otherwise uninteresting. Force it to have the
+ // scope line.
+ unsigned ScopeLine = SP->getScopeLine();
+ DILocation *ScopeLineDILoc =
+ DILocation::get(SP->getContext(), ScopeLine, 0, SP);
+ const_cast<MachineInstr*>(&*RIt)->setDebugLoc(ScopeLineDILoc);
+
+ // Consider this position to be where prologue_end is placed.
+ return std::make_pair(&*RIt, false);
+ }
+ }
+
// Try to continue searching, but use a backup-location if substantive
// computation is happening.
auto NextInst = std::next(CurInst);
diff --git a/llvm/test/DebugInfo/X86/no-prologue-end-after-line0-calls.mir b/llvm/test/DebugInfo/X86/no-prologue-end-after-line0-calls.mir
index b3efc0321c2af..cf16455b88602 100644
--- a/llvm/test/DebugInfo/X86/no-prologue-end-after-line0-calls.mir
+++ b/llvm/test/DebugInfo/X86/no-prologue-end-after-line0-calls.mir
@@ -1,4 +1,4 @@
-# RUN: llc %s -start-after=livedebugvalues -o - -filetype=obj | llvm-dwarfdump - --debug-line | FileCheck %s --implicit-check-not=prologue_end
+# RUN: llc %s -start-after=livedebugvalues -o - -filetype=obj | llvm-dwarfdump - --debug-line | FileCheck %s
#
## Original code, compiled clang -O2 -g -c
##
@@ -23,25 +23,25 @@
## a: 59 pop %rcx
## b: c3 ret
##
-## Where prologue_end is placed on address 8, the clearing of the return
-## register, because it's the first "real" instruction that isn't line zero.
-## This then causes debuggers to skip over the call instruction when entering
-## the function, which is catastrophic.
+## And we could choose to set prologue_end on address 8, the clearing of the
+## return register, because it's the first "real" instruction that isn't line
+## zero. But this then causes debuggers to skip over the call instruction when
+## entering the function, which is catastrophic.
##
-## Instead: we shouldn't put a prologue_end on this function at all. It's too
-## deformed from the original code to truly have a position (with a line number)
-## that is both true, and after frame setup. This gives consumers the
+## Instead: we force the xor at address 1 to have a source location (the
+## function scope line number), and put a prologue_end there. While it's a
+## setup instruction, it's better to have a prologue_end that's still slightly
+## in the prologue than to step over the call. This gives consumers the
## opportunity to recognise "this is a crazy function" and act accordingly.
##
-## Check lines ensure that there's something meaningful in the line table
-## involving line 2, the implicit-check-not is making sure there isn't a
-## prologue_end flag on any line entry.
+## Check lines: the first entry is the start-of-function scope line, the second
+## entry is the prologue_end on the xor, while the third is the zero-line-number
+## call instruction.
#
-# CHECK: standard_opcode_lengths[DW_LNS_set_prologue_end] = 0
-#
-# CHECK: Address Line Column File
-# CHECK: 2 0 0
-# CHECK: end_sequence
+# CHECK: 2 0 0 0 0 0 is_stmt
+# CHECK-NEXT: 2 0 0 0 0 0 is_stmt prologue_end
+# CHECK-NEXT: 0 0 0 0 0 0
+
--- |
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
>From ccb24a303b477c42b0201698cced3608404b00e4 Mon Sep 17 00:00:00 2001
From: Jeremy Morse <jeremy.morse at sony.com>
Date: Mon, 17 Nov 2025 13:37:15 +0000
Subject: [PATCH 4/4] Put prologue_end on the line-zero call, rotate tests
---
llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp | 29 ++++++---------
.../X86/no-prologue-end-after-line0-calls.mir | 37 +++++++++++--------
2 files changed, 33 insertions(+), 33 deletions(-)
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index a8904a46dd571..2a765a795f4cd 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -2211,6 +2211,11 @@ void DwarfDebug::beginInstruction(const MachineInstr *MI) {
PrevInstLoc = DL;
}
+// Returns the position where we should place prologue_end, potentially nullptr,
+// which means "no good place to put prologue_end". Returns true in the second
+// return value if there are no setup instructions in this function at all,
+// meaning we should not emit a start-of-function linetable entry, because it
+// would be zero-lengthed.
static std::pair<const MachineInstr *, bool>
findPrologueEndLoc(const MachineFunction *MF) {
// First known non-DBG_VALUE and non-frame setup location marks
@@ -2308,31 +2313,21 @@ findPrologueEndLoc(const MachineFunction *MF) {
// In very rare scenarios function calls can have line zero, and we
// shouldn't step over such a call while trying to reach prologue_end. In
- // these extraordinary conditions, force an earlier setup instruction to
- // have the scope line and put prologue_end there. This will be suboptimal,
- // and might still be in setup code, but is less catastrophic than missing
- // a call.
+ // these extraordinary conditions, force the call to have the scope line
+ // and put prologue_end there. This isn't ideal, but signals that the call
+ // is where execution in the function starts, and is less catastrophic than
+ // stepping over the call.
if (CurInst->isCall()) {
if (const DILocation *Loc = CurInst->getDebugLoc().get();
Loc && Loc->getLine() == 0) {
- // Go back one instruction.
- auto RIt = std::next(CurInst->getIterator().getReverse());
- // In the radically unlikely event that there's no prior instruction,
- // meaning the first instruction in the function is a call, don't set a
- // prologue_end at all.
- if (RIt == CurInst->getParent()->rend())
- return std::make_pair(nullptr, true);
-
- // The prior instruction was either line-zero or unset, or a setup
- // instruction, or otherwise uninteresting. Force it to have the
- // scope line.
+ // Create and assign the scope-line position.
unsigned ScopeLine = SP->getScopeLine();
DILocation *ScopeLineDILoc =
DILocation::get(SP->getContext(), ScopeLine, 0, SP);
- const_cast<MachineInstr*>(&*RIt)->setDebugLoc(ScopeLineDILoc);
+ const_cast<MachineInstr*>(&*CurInst)->setDebugLoc(ScopeLineDILoc);
// Consider this position to be where prologue_end is placed.
- return std::make_pair(&*RIt, false);
+ return std::make_pair(&*CurInst, false);
}
}
diff --git a/llvm/test/DebugInfo/X86/no-prologue-end-after-line0-calls.mir b/llvm/test/DebugInfo/X86/no-prologue-end-after-line0-calls.mir
index cf16455b88602..abd7eb2528cb0 100644
--- a/llvm/test/DebugInfo/X86/no-prologue-end-after-line0-calls.mir
+++ b/llvm/test/DebugInfo/X86/no-prologue-end-after-line0-calls.mir
@@ -1,4 +1,4 @@
-# RUN: llc %s -start-after=livedebugvalues -o - -filetype=obj | llvm-dwarfdump - --debug-line | FileCheck %s
+# RUN: llc %s -start-after=livedebugvalues -o - | FileCheck %s
#
## Original code, compiled clang -O2 -g -c
##
@@ -28,19 +28,30 @@
## zero. But this then causes debuggers to skip over the call instruction when
## entering the function, which is catastrophic.
##
-## Instead: we force the xor at address 1 to have a source location (the
-## function scope line number), and put a prologue_end there. While it's a
-## setup instruction, it's better to have a prologue_end that's still slightly
+## Instead: force the call itself to have a source location (the function scope
+## line number), and put a prologue_end there. While it's not the original
+## source of the call, it's better to have a prologue_end that means we'll stop
## in the prologue than to step over the call. This gives consumers the
## opportunity to recognise "this is a crazy function" and act accordingly.
##
-## Check lines: the first entry is the start-of-function scope line, the second
-## entry is the prologue_end on the xor, while the third is the zero-line-number
-## call instruction.
+## Check lines: ensure that we set prologue_end. The first entry is the
+## start-of-function scope line, the second entry is the prologue_end on the
+## call.
#
-# CHECK: 2 0 0 0 0 0 is_stmt
-# CHECK-NEXT: 2 0 0 0 0 0 is_stmt prologue_end
-# CHECK-NEXT: 0 0 0 0 0 0
+#
+# CHECK: main:
+# CHECK-NEXT: .Lfunc_begin0:
+# CHECK-NEXT: .file 0 "/tmp/test.c"
+# CHECK-NEXT: .loc 0 2 0
+# CHECK-NEXT: .cfi_startproc
+# CHECK-NEXT: # %bb.0:
+# CHECK-NEXT: pushq %rax
+# CHECK-NEXT: .cfi_def_cfa_offset 16
+# CHECK-NEXT: .Ltmp0:
+# CHECK-NEXT: .loc 0 0 0 is_stmt 0
+# CHECK-NEXT: xorl %eax, %eax
+# CHECK-NEXT: .loc 0 2 0 prologue_end is_stmt 1
+# CHECK-NEXT: callq ext at PLT
--- |
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
@@ -49,8 +60,6 @@
; Function Attrs: nounwind uwtable
define dso_local noundef i32 @main(i32 noundef %argc, ptr noundef readnone captures(none) %argv) local_unnamed_addr !dbg !10 {
entry:
- #dbg_value(i32 %argc, !19, !DIExpression(), !21)
- #dbg_value(ptr %argv, !20, !DIExpression(), !21)
tail call void (...) @ext(), !dbg !22
ret i32 0, !dbg !24
}
@@ -112,14 +121,10 @@ machineFunctionInfo:
amxProgModel: None
body: |
bb.0.entry:
- DBG_VALUE $edi, $noreg, !19, !DIExpression(), debug-location !21
- DBG_VALUE $rsi, $noreg, !20, !DIExpression(), debug-location !21
frame-setup PUSH64r undef $rax, implicit-def $rsp, implicit $rsp
frame-setup CFI_INSTRUCTION def_cfa_offset 16
dead $eax = XOR32rr undef $eax, undef $eax, implicit-def dead $eflags, implicit-def $al, debug-location !22
CALL64pcrel32 target-flags(x86-plt) @ext, csr_64, implicit $rsp, implicit $ssp, implicit killed $al, implicit-def $rsp, implicit-def $ssp, debug-location !22
- DBG_VALUE $rsi, $noreg, !20, !DIExpression(DW_OP_LLVM_entry_value, 1), debug-location !21
- DBG_VALUE $edi, $noreg, !19, !DIExpression(DW_OP_LLVM_entry_value, 1), debug-location !21
$eax = XOR32rr undef $eax, undef $eax, implicit-def dead $eflags, debug-location !24
$rcx = frame-destroy POP64r implicit-def $rsp, implicit $rsp, debug-location !24
frame-destroy CFI_INSTRUCTION def_cfa_offset 8, debug-location !24
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