[llvm] 04e5b7f - AArch64: fall back to DWARF instead of crashing on weird .cfi directives

[Tim Northover via llvm-commits]

Author: Tim Northover
Date: 2022-05-18T11:42:42+01:00
New Revision: 04e5b7fd17748bd10ae0f30cb571103e5da0dde5

URL: https://github.com/llvm/llvm-project/commit/04e5b7fd17748bd10ae0f30cb571103e5da0dde5
DIFF: https://github.com/llvm/llvm-project/commit/04e5b7fd17748bd10ae0f30cb571103e5da0dde5.diff

LOG: AArch64: fall back to DWARF instead of crashing on weird .cfi directives

CodeGen will only produce fixed formwat prologues, but hand-written assembly
can have .cfi directives in any combination they want. This should cause a
fallback to DWARF rather than an assertion failure (or an incorrect compact
unwind if assertions are disabled).

Added: 
    

Modified: 
    llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp
    llvm/test/MC/AArch64/arm64-compact-unwind-fallback.s

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp
index 85b221286ecd0..c1188d1c139e5 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp
@@ -593,17 +593,18 @@ class DarwinAArch64AsmBackend : public AArch64AsmBackend {
         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!");
+        if (i + 2 >= e)
+          return CU::UNWIND_ARM64_MODE_DWARF;
 
         const MCCFIInstruction &LRPush = Instrs[++i];
-        assert(LRPush.getOperation() == MCCFIInstruction::OpOffset &&
-               "Link register not pushed!");
+        if (LRPush.getOperation() != MCCFIInstruction::OpOffset)
+          return CU::UNWIND_ARM64_MODE_DWARF;
         const MCCFIInstruction &FPPush = Instrs[++i];
-        assert(FPPush.getOperation() == MCCFIInstruction::OpOffset &&
-               "Frame pointer not pushed!");
+        if (FPPush.getOperation() != MCCFIInstruction::OpOffset)
+          return CU::UNWIND_ARM64_MODE_DWARF;
 
-        assert(FPPush.getOffset() + 8 == LRPush.getOffset());
+        if (FPPush.getOffset() + 8 != LRPush.getOffset())
+          return CU::UNWIND_ARM64_MODE_DWARF;
         CurOffset = FPPush.getOffset();
 
         unsigned LRReg = *MRI.getLLVMRegNum(LRPush.getRegister(), true);
@@ -612,8 +613,8 @@ class DarwinAArch64AsmBackend : public AArch64AsmBackend {
         LRReg = getXRegFromWReg(LRReg);
         FPReg = getXRegFromWReg(FPReg);
 
-        assert(LRReg == AArch64::LR && FPReg == AArch64::FP &&
-               "Pushing invalid registers for frame!");
+        if (LRReg != AArch64::LR || FPReg != AArch64::FP)
+          return CU::UNWIND_ARM64_MODE_DWARF;
 
         // Indicate that the function has a frame.
         CompactUnwindEncoding |= CU::UNWIND_ARM64_MODE_FRAME;

diff  --git a/llvm/test/MC/AArch64/arm64-compact-unwind-fallback.s b/llvm/test/MC/AArch64/arm64-compact-unwind-fallback.s
index 12525b78a274b..317b67130cdcd 100644
--- a/llvm/test/MC/AArch64/arm64-compact-unwind-fallback.s
+++ b/llvm/test/MC/AArch64/arm64-compact-unwind-fallback.s
@@ -6,6 +6,8 @@
 // CHECK: Contents of __compact_unwind section:
 // CHECK: compact encoding:     0x03000000
 // CHECK: compact encoding:     0x03000000
+// CHECK: compact encoding:     0x03000000
+// CHECK: compact encoding:     0x03000000
 
 // CHECK: .eh_frame contents:
 // CHECK: DW_CFA_def_cfa: reg1 +32
@@ -23,3 +25,16 @@ _cfi_dwarf1:
  .cfi_def_cfa_offset 32
  .cfi_def_cfa_offset 64
  .cfi_endproc
+
+_cfi_dwarf2:
+  .cfi_startproc
+  .cfi_def_cfa w29, 16
+  .cfi_def_cfa w29, 16
+  .cfi_endproc
+
+_cfi_dwarf3:
+  .cfi_startproc
+  .cfi_def_cfa w29, 16
+  .cfi_offset w16, -16
+  .cfi_offset w17, -8
+  .cfi_endproc