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ARM MC: Fix the initial DWARF CFI unwind info at the start of a function

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This brings MC into line with GNU 'as' on ARM, and it brings the ARM
target into line with most other LLVM targets, which declare the
initial CFI state with addInitialFrameState().

Without this, functions generated with .cfi_startproc/endproc on ARM
will tend to cause GDB to abort with:
  gdb/dwarf2-frame.c:1132: internal-error: Unknown CFA rule.

I've also tested this by comparing the output of "readelf -w" on the
object files produced by llvm-mc and gas when given the .s file added
here.

This change is part of addressing PR18636.

Differential Revision: http://llvm-reviews.chandlerc.com/D2597

llvm-svn: 200255
This commit is contained in:
Mark Seaborn 2014-01-27 22:38:14 +00:00
parent 0719e41557
commit 1b9cb5e4a2
2 changed files with 24 additions and 2 deletions
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10
lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.cpp
View File

@ -212,10 +212,16 @@ static MCRegisterInfo *createARMMCRegisterInfo(StringRef Triple) {
static MCAsmInfo *createARMMCAsmInfo(const MCRegisterInfo &MRI, StringRef TT) { static MCAsmInfo *createARMMCAsmInfo(const MCRegisterInfo &MRI, StringRef TT) {
Triple TheTriple(TT); Triple TheTriple(TT);
MCAsmInfo *MAI;
if (TheTriple.isOSBinFormatMachO()) if (TheTriple.isOSBinFormatMachO())
return new ARMMCAsmInfoDarwin(); MAI = new ARMMCAsmInfoDarwin();
else
MAI = new ARMELFMCAsmInfo();
return new ARMELFMCAsmInfo(); unsigned Reg = MRI.getDwarfRegNum(ARM::SP, true);
MAI->addInitialFrameState(MCCFIInstruction::createDefCfa(0, Reg, 0));
return MAI;
} }
static MCCodeGenInfo *createARMMCCodeGenInfo(StringRef TT, Reloc::Model RM, static MCCodeGenInfo *createARMMCCodeGenInfo(StringRef TT, Reloc::Model RM,

16
test/MC/ARM/dwarf-cfi-initial-state.s Normal file
View File

@ -0,0 +1,16 @@
# RUN: llvm-mc < %s -triple=armv7-linux-gnueabi -filetype=obj -o - \
# RUN: | llvm-dwarfdump - | FileCheck %s
.cfi_sections .debug_frame
.cfi_startproc
bx lr
.cfi_endproc
# CHECK: .debug_frame contents:
# CHECK: CIE
# CHECK-NOT: DW_CFA
# When llvm-dwarfdump prints the full info for the DW_CFA_def_cfa
# field, we can check that here too.
# CHECK: DW_CFA_def_cfa:
# CHECK-NOT: DW_CFA
# CHECK: FDE