Skip to content

[AArch64] Force dwarf unwind for MTE-tagged stack frames #168530

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 2 commits into
base: main
Choose a base branch
from
+32 −0
Open

[AArch64] Force dwarf unwind for MTE-tagged stack frames #168530

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
754f1ca
[AArch64] Force dwarf unwind for MTE-tagged stack frames
DanBlackwell Nov 18, 2025
ec9dc47
Add test
DanBlackwell Nov 19, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
5 changes: 5 additions & 0 deletions llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -586,6 +586,11 @@ class DarwinAArch64AsmBackend : public AArch64AsmBackend {
/// Generate the compact unwind encoding from the CFI directives.
uint64_t generateCompactUnwindEncoding(const MCDwarfFrameInfo *FI,
const MCContext *Ctxt) const override {
// MTE-tagged frames must use DWARF unwinding because compact unwind
// doesn't handle MTE tags
if (FI->IsMTETaggedFrame)
return CU::UNWIND_ARM64_MODE_DWARF;

ArrayRef<MCCFIInstruction> Instrs = FI->Instructions;
if (Instrs.empty())
return CU::UNWIND_ARM64_MODE_FRAMELESS;
Expand Down
27 changes: 27 additions & 0 deletions llvm/test/CodeGen/AArch64/memtag-compact-unwind.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,27 @@
; RUN: llc -mtriple=arm64-apple-macosx -mattr=+mte %s -filetype=obj -o %t.o
; RUN: llvm-objdump --unwind-info %t.o | FileCheck %s

; Frames with MTE stack tagging must use DWARF unwinding because compact unwind
; doesn't handle MTE tag untagging during exception unwinding.

; MTE-tagged frame should use DWARF mode (0x03000000)
; CHECK-LABEL: Contents of __compact_unwind section:
; CHECK: compact encoding: 0x03000000

; Normal frame should NOT use DWARF mode
; CHECK-NOT: compact encoding: 0x03000000
; CHECK: compact encoding: 0x{{[0-9a-f]+}}

define void @mte_tagged_frame() sanitize_memtag "frame-pointer"="all" {
%x = alloca i32, align 4
store i32 42, ptr %x
call void asm sideeffect "", "r"(ptr %x)
ret void
}

define void @normal_frame() "frame-pointer"="all" {
%x = alloca i32, align 4
store i32 42, ptr %x
call void asm sideeffect "", "r"(ptr %x)
ret void
}