[DebugInfo][DWARF] Use DW_AT_call_target_clobbered for exprs with volatile regs #172167
+113
−9
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
…atile regs
Without this patch DW_AT_call_target is used for all indirect call address
location expressions. The DWARF spec says:
For indirect calls or jumps where the address is not computable without use
of registers or memory locations that might be clobbered by the call the
DW_AT_call_target_clobbered attribute is used instead of the
DW_AT_call_target attribute.
This patch implements that behaviour.
OCHyams
requested review from
CarlosAlbertoEnciso,
Michael137,
SLTozer,
ayermolo,
dzhidzhoev,
jmorse and
jryans
Member
|
@llvm/pr-subscribers-debuginfo Author: Orlando Cazalet-Hyams (OCHyams) ChangesWithout this patch DW_AT_call_target is used for all indirect call address location expressions. The DWARF spec says: This patch implements that behaviour. Full diff: https://github.com/llvm/llvm-project/pull/172167.diff 4 Files Affected:
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index d19de7f8000ec..c0421e628c7e9 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -1328,15 +1328,22 @@ DIE &DwarfCompileUnit::constructCallSiteEntryDIE(
// A valid register in CallTarget indicates an indirect call.
if (CallTarget.getReg()) {
+ // Add a DW_AT_call_target location expression describing the location of
+ // the address of the target function. If any register in the expression
+ // (i.e., the single register we currently handle) is volatile we must use
+ // DW_AT_call_target_clobbered instead.
+ const TargetRegisterInfo &TRI = *Asm->MF->getSubtarget().getRegisterInfo();
+ dwarf::Attribute Attribute = getDwarf5OrGNUAttr(
+ TRI.isCalleeSavedPhysReg(CallTarget.getReg(), *Asm->MF)
+ ? dwarf::DW_AT_call_target
+ : dwarf::DW_AT_call_target_clobbered);
+
// CallTarget is the location of the address of an indirect call. The
// location may be indirect, modified by Offset.
if (CallTarget.isIndirect())
- addMemoryLocation(CallSiteDIE,
- getDwarf5OrGNUAttr(dwarf::DW_AT_call_target),
- CallTarget, Offset);
+ addMemoryLocation(CallSiteDIE, Attribute, CallTarget, Offset);
else
- addAddress(CallSiteDIE, getDwarf5OrGNUAttr(dwarf::DW_AT_call_target),
- CallTarget);
+ addAddress(CallSiteDIE, Attribute, CallTarget);
} else if (CalleeSP) {
DIE *CalleeDIE = getOrCreateSubprogramDIE(CalleeSP, CalleeF);
assert(CalleeDIE && "Could not create DIE for call site entry origin");
diff --git a/llvm/test/DebugInfo/X86/dwarf-call-target-clobbered.mir b/llvm/test/DebugInfo/X86/dwarf-call-target-clobbered.mir
new file mode 100644
index 0000000000000..ff5c78d7ad1cf
--- /dev/null
+++ b/llvm/test/DebugInfo/X86/dwarf-call-target-clobbered.mir
@@ -0,0 +1,96 @@
+# RUN: llc %s --start-after=livedebugvalues -o - --filetype=obj | llvm-dwarfdump - | FileCheck %s
+
+## Check that DW_AT_call_target_clobbered is used for a location expression
+## using a volatile register, otherwise DW_AT_call_target is used.
+
+## Generated from this C++ with llc -stop-after=livedebugvalues -simplify-mir:
+## __attribute__((disable_tail_calls)) void call_mem(void (**f)()) {
+## (*f)();
+## (*f)();
+## }
+
+## Which disassembles to -
+## 0000000000000000 <_Z8call_memPPFvvE>:
+## 0: 53 pushq %rbx
+## 1: 48 89 fb movq %rdi, %rbx
+## 4: ff 17 callq *(%rdi)
+## 6: ff 13 callq *(%rbx)
+## 8: 5b popq %rbx
+## 9: c3 retq
+
+# CHECK: DW_TAG_call_site
+# CHECK-NEXT: DW_AT_call_target_clobbered (DW_OP_breg5 RDI+0)
+# CHECK: DW_TAG_call_site
+# CHECK-NEXT: DW_AT_call_target (DW_OP_breg3 RBX+0)
+
+--- |
+ target triple = "x86_64-unknown-linux-gnu"
+
+ define dso_local void @_Z8call_memPPFvvE(ptr noundef readonly captures(none) %f) local_unnamed_addr !dbg !5 {
+ entry:
+ %0 = load ptr, ptr %f, align 8, !dbg !13
+ call void %0(), !dbg !13
+ %1 = load ptr, ptr %f, align 8, !dbg !14
+ call void %1(), !dbg !14
+ ret void
+ }
+
+ !llvm.dbg.cu = !{!0}
+ !llvm.module.flags = !{!2, !3}
+ !llvm.ident = !{!4}
+
+ !0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 22.0.0git", isOptimized: true, 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}
+ !4 = !{!"clang version 22.0.0git"}
+ !5 = distinct !DISubprogram(name: "call_mem", linkageName: "_Z8call_memPPFvvE", scope: !1, file: !1, line: 1, type: !6, scopeLine: 1, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !12)
+ !6 = !DISubroutineType(types: !7)
+ !7 = !{null, !8}
+ !8 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !9, size: 64)
+ !9 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !10, size: 64)
+ !10 = !DISubroutineType(types: !11)
+ !11 = !{null}
+ !12 = !{}
+ !13 = !DILocation(line: 2, scope: !5)
+ !14 = !DILocation(line: 3, scope: !5)
+...
+---
+name: _Z8call_memPPFvvE
+alignment: 16
+tracksRegLiveness: true
+noPhis: true
+isSSA: false
+noVRegs: true
+hasFakeUses: false
+debugInstrRef: true
+tracksDebugUserValues: true
+liveins:
+ - { reg: '$rdi' }
+frameInfo:
+ stackSize: 8
+ offsetAdjustment: -8
+ maxAlignment: 1
+ adjustsStack: true
+ hasCalls: true
+ maxCallFrameSize: 0
+ cvBytesOfCalleeSavedRegisters: 8
+ isCalleeSavedInfoValid: true
+fixedStack:
+ - { id: 0, type: spill-slot, offset: -16, size: 8, alignment: 16, callee-saved-register: '$rbx' }
+machineFunctionInfo:
+ amxProgModel: None
+body: |
+ bb.0.entry:
+ liveins: $rdi, $rbx
+
+ frame-setup PUSH64r killed $rbx, implicit-def $rsp, implicit $rsp
+ frame-setup CFI_INSTRUCTION def_cfa_offset 16
+ CFI_INSTRUCTION offset $rbx, -16
+ $rbx = MOV64rr $rdi
+ CALL64m $rdi, 1, $noreg, 0, $noreg, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, debug-location !13 :: (load (s64) from %ir.f)
+ CALL64m killed renamable $rbx, 1, $noreg, 0, $noreg, csr_64, implicit $rsp, implicit $ssp, implicit-def $rsp, implicit-def $ssp, debug-location !14 :: (load (s64) from %ir.f)
+ $rbx = frame-destroy POP64r implicit-def $rsp, implicit $rsp
+ frame-destroy CFI_INSTRUCTION def_cfa_offset 8
+ RET64
+...
diff --git a/llvm/test/DebugInfo/X86/dwarf-call-target-mem-loc.mir b/llvm/test/DebugInfo/X86/dwarf-call-target-mem-loc.mir
index ef8a080cebaae..1923baf9fa173 100644
--- a/llvm/test/DebugInfo/X86/dwarf-call-target-mem-loc.mir
+++ b/llvm/test/DebugInfo/X86/dwarf-call-target-mem-loc.mir
@@ -1,10 +1,11 @@
# RUN: llc %s --start-after=livedebugvalues -o - --filetype=obj | llvm-dwarfdump - | FileCheck %s
## Check the memory location of the target address for the indirect call
-## (virtual in this case) is described by a DW_AT_call_target expression.
+## (virtual in this case) is described by a DW_AT_call_target_clobbered
+## expression.
# CHECK: DW_TAG_call_site
-# CHECK-NEXT: DW_AT_call_target (DW_OP_breg0 RAX+8)
+# CHECK-NEXT: DW_AT_call_target_clobbered (DW_OP_breg0 RAX+8)
## Generated from this C++ with llc -stop-after=livedebugvalues -simplify-mir:
## struct Base {
diff --git a/llvm/test/DebugInfo/X86/dwarf-callsite-related-attrs-indirect.ll b/llvm/test/DebugInfo/X86/dwarf-callsite-related-attrs-indirect.ll
index f64b78f5820e4..70f91c66d4e58 100644
--- a/llvm/test/DebugInfo/X86/dwarf-callsite-related-attrs-indirect.ll
+++ b/llvm/test/DebugInfo/X86/dwarf-callsite-related-attrs-indirect.ll
@@ -18,7 +18,7 @@ entry:
#dbg_value(ptr %f, !17, !DIExpression(), !18)
; OBJ: DW_TAG_call_site
-; OBJ: DW_AT_call_target (DW_OP_reg[[#]] {{.*}})
+; OBJ: DW_AT_call_target{{(_clobbered)?}} (DW_OP_reg[[#]] {{.*}})
; OBJ: DW_AT_call_return_pc
call void (...) %f() #1, !dbg !19
ret void, !dbg !20
@@ -33,7 +33,7 @@ entry:
%0 = load ptr, ptr %f, align 8, !dbg !28, !tbaa !29
; OBJ: DW_TAG_call_site
-; OBJ: DW_AT_call_target (DW_OP_breg[[#]] {{.*}})
+; OBJ: DW_AT_call_target{{(_clobbered)?}} (DW_OP_breg[[#]] {{.*}})
; OBJ: DW_AT_call_return_pc
call void (...) %0() #1, !dbg !28
ret void, !dbg !33
|
Collaborator
|
LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/155/builds/15726 Here is the relevant piece of the build log for the reference |
Contributor
Author
Looks like an intermittent failure that has righted itself since. |
Collaborator
|
We're seeing compiler crashes with after this. I have an unreduced repro at https://issues.chromium.org/u/1/issues/468825583#comment2 Can you take a look? |
Collaborator
|
I guess reducing was fast :) |
Contributor
Author
|
Thanks for the reduced reproducer, taking a look! |
OCHyams
added a commit
to OCHyams/llvm-project
that referenced
this pull request
Dec 15, 2025
Fixes assertion trip introduced in llvm#172167 See https://issues.chromium.org/issues/468825583#comment2
Contributor
Author
|
Just missed a simple lookup used for some configurations - fix here #172336 |
OCHyams
added a commit
that referenced
this pull request
Dec 15, 2025
Fixes assertion trip introduced in #172167 See https://issues.chromium.org/issues/468825583#comment2
This was referenced Dec 15, 2025
OCHyams
added a commit
that referenced
this pull request
Dec 17, 2025
) Not sure whether this comes up in practice, but I noticed a switch block I missed in #172167
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
5 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Without this patch DW_AT_call_target is used for all indirect call address location expressions. The DWARF spec says:
This patch implements that behaviour.