[MC] Fallback on DWARF when generating compact unwind on AArch64
Instead of asserting when using the def_cfa directive with a register
different from fp, fallback on DWARF.
Easily triggered with:
.cfi_def_cfa x1, 32;
rdar://40249694
Differential Revision: https://reviews.llvm.org/D47593
llvm-svn: 333667
diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp
index 998a5ef..c391114 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp
@@ -455,9 +455,17 @@
return CU::UNWIND_ARM64_MODE_DWARF;
case MCCFIInstruction::OpDefCfa: {
// Defines a frame pointer.
- assert(getXRegFromWReg(MRI.getLLVMRegNum(Inst.getRegister(), true)) ==
- AArch64::FP &&
- "Invalid frame pointer!");
+ unsigned XReg =
+ getXRegFromWReg(MRI.getLLVMRegNum(Inst.getRegister(), true));
+
+ // Other CFA registers than FP are not supported by compact unwind.
+ // Fallback on DWARF.
+ // FIXME: When opt-remarks are supported in MC, add a remark to notify
+ // the user.
+ if (XReg != AArch64::FP)
+ return CU::UNWIND_ARM64_MODE_DWARF;
+
+ assert(XReg == AArch64::FP && "Invalid frame pointer!");
assert(i + 2 < e && "Insufficient CFI instructions to define a frame!");
const MCCFIInstruction &LRPush = Instrs[++i];