[DebugInfo] Fix dumping CIE ID in .eh_frame sections.

[ikudrin]

Summary

We do not keep the actual value of the CIE_id field, because it is predefined, and use a constant when dumping a CIE record. The issue was that the predefined value is different for .debug_frame and .eh_frame sections, but we always printed the same. The patch fixes that by choosing an appropriate constant to print.

[probinson]

Can you point to a reference specifying this difference?

[ikudrin]

In D73627#1849917, @probinson wrote:

Can you point to a reference specifying this difference?

For example, https://refspecs.linuxfoundation.org/LSB_3.0.0/LSB-Core-generic/LSB-Core-generic/ehframechpt.html or https://www.airs.com/blog/archives/460.

[luismarques]

LGTM.

[probinson]

IIUC, this patch expresses the difference between (32-bit) .debug_frame and .eh_frame, while D73887 takes care of the 64-bit case.
As long as the commit message has the link to the .eh_frame spec (which I think is harder to find than the DWARF spec), LGTM.

lld/test/ELF/eh-frame-hdr-augmentation.s

 // REQUIRES: x86
 // RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
 // RUN: ld.lld --hash-style=sysv --eh-frame-hdr %t.o -o %t -shared
 // RUN: llvm-objdump --dwarf=frames %t | FileCheck %s
 
 // CHECK: .eh_frame contents:
 
-// CHECK:      00000000 0000001c ffffffff CIE
+// CHECK:      00000000 0000001c 00000000 CIE
 // CHECK-NEXT:   Version:                       1
 // CHECK-NEXT:   Augmentation:             "zPLR"
 // CHECK-NEXT:   Code alignment factor: 1
 // CHECK-NEXT:   Data alignment factor: -8
 // CHECK-NEXT:   Return address column: 16
 // CHECK-NEXT:   Personality Address: 0000000000001029
 // CHECK-NEXT:   Augmentation data:
 

llvm/lib/DebugInfo/DWARF/DWARFDebugFrame.cpp

for (const auto &Instr : Instructions) {
     for (unsigned i = 0; i < Instr.Ops.size(); ++i)
       printOperand(OS, MRI, IsEH, Instr, i, Instr.Ops[i]);
     OS << '\n';
   }
 }
 
 void CIE::dump(raw_ostream &OS, const MCRegisterInfo *MRI, bool IsEH) const {
   OS << format("%08x %08x %08x CIE", (uint32_t)Offset, (uint32_t)Length,
-               DW_CIE_ID)
+               IsEH ? 0 : DW_CIE_ID)
      << "\n";
   OS << format("  Version:               %d\n", Version);
   OS << "  Augmentation:          \"" << Augmentation << "\"\n";
   if (Version >= 4) {
     OS << format("  Address size:          %u\n", (uint32_t)AddressSize);
     OS << format("  Segment desc size:     %u\n",
                  (uint32_t)SegmentDescriptorSize);
   }

llvm/test/DebugInfo/RISCV/eh-frame.s

 # RUN: llvm-mc -filetype=obj -triple=riscv32 < %s | llvm-dwarfdump -eh-frame - \
 # RUN:    | FileCheck --check-prefixes=CHECK,RV32 %s
 # RUN: llvm-mc -filetype=obj -triple=riscv64 < %s | llvm-dwarfdump -eh-frame - \
 # RUN:    | FileCheck --check-prefixes=CHECK,RV64 %s
 
 func:
   .cfi_startproc
   ret
   .cfi_endproc
 
-# CHECK: 00000000 00000010 ffffffff CIE
+# CHECK: 00000000 00000010 00000000 CIE
 # CHECK:   Version:               1
 # CHECK:   Augmentation:          "zR"
 # CHECK:   Code alignment factor: 1
 
 # TODO: gas uses -4 for the data alignment factor for both RV32 and RV64. They
 # do so on the basis that on RV64F, F registers may only be 4 bytes
 # (DWARF2_CIE_DATA_ALIGNMENT).
 

llvm/test/MC/Mips/eh-frame.s

 // RELOCS:      Relocations [
 // RELOCS:        Section ({{.+}}) .rel{{a?}}.eh_frame {
 // ABS32-NEXT:      R_MIPS_32
 // ABS64-NEXT:      R_MIPS_64/R_MIPS_NONE/R_MIPS_NONE
 // PIC32-NEXT:      R_MIPS_PC32
 // PIC64-NEXT:      R_MIPS_PC32/R_MIPS_NONE/R_MIPS_NONE
 // RELOCS-NEXT:   }
 
-// DWARF32: 00000000 00000010 ffffffff CIE
+// DWARF32: 00000000 00000010 00000000 CIE
 // DWARF32-NEXT:     Version:               1
 // DWARF32-NEXT:     Augmentation:          "zR"
 // DWARF32-NEXT:     Code alignment factor: 1
 // DWARF32-NEXT:     Data alignment factor: -4
 // DWARF32-NEXT:     Return address column: 31
 // DWARF32_ABS-NEXT: Augmentation data: 0B
 //                                      ^^ fde pointer encoding: DW_EH_PE_sdata4
 // DWARF32_PIC-NEXT: Augmentation data: 1B
 //                                      ^^ fde pointer encoding: DW_EH_PE_pcrel | DW_EH_PE_sdata4
 // DWARF32-EMPTY:
 // DWARF32-NEXT:     DW_CFA_def_cfa_register: reg29
 //
 // DWARF32: 00000014 00000010 00000018 FDE cie=00000018 pc=00000000...00000000
 // DWARF32-NEXT:     DW_CFA_nop:
 // DWARF32-NEXT:     DW_CFA_nop:
 // DWARF32-NEXT:     DW_CFA_nop:
 
 
-// DWARF64: 00000000 00000010 ffffffff CIE
+// DWARF64: 00000000 00000010 00000000 CIE
 // DWARF64-NEXT:     Version:               1
 // DWARF64-NEXT:     Augmentation:          "zR"
 // DWARF64-NEXT:     Code alignment factor: 1
 // DWARF64-NEXT:     Data alignment factor: -8
 //                                          ^^ GAS uses -4. Should be ok as long as
 //                                             all offsets we need are a multiple of 8.
 // DWARF64-NEXT:     Return address column: 31
 // DWARF64_ABS-NEXT: Augmentation data: 0C

llvm/test/MC/X86/return-column.s

h:
   .cfi_return_column 65
   .cfi_endproc
 
 // CHECK-ASM-ROUNDTRIP-LABEL: f:
 // CHECK-ASM-ROUNDTRIP: .cfi_startproc
 // CHECK-ASM-ROUNDTRIP-NEXT: .cfi_return_column 0
 // CHECK-ASM-ROUNDTRIP: .cfi_endproc
 
-// CHECK-EH_FRAME: 00000000 00000014 ffffffff CIE
+// CHECK-EH_FRAME: 00000000 00000014 00000000 CIE
 // CHECK-EH_FRAME:   Return address column: 0
 
-// CHECK-EH_FRAME: 0000002c 00000014 ffffffff CIE
+// CHECK-EH_FRAME: 0000002c 00000014 00000000 CIE
 // CHECK-EH_FRAME:   Return address column: 65
 
-// CHECK-EH_FRAME-NOT: ........ 00000014 ffffffff CIE
+// CHECK-EH_FRAME-NOT: ........ 00000014 00000000 CIE
 

llvm/test/tools/llvm-dwarfdump/X86/eh-frame-return-address-reg.s

 # RUN: llvm-mc %s -filetype obj -triple x86_64-pc-linux -o %t.o
 # RUN: llvm-dwarfdump -v %t.o | FileCheck %s
 
 # The format of the .eh_frame section is similar in
 # format and purpose to the .debug_frame section.
 # Version 1 is often used for .eh_frame,
 # and also it was used for DWARF v2. For that case,
 # return address register should be encoded as ubyte,
 # while later versions use ULEB128. This test case
 # checks that we are able to dump it correctly.
 
 # CHECK:      .eh_frame contents:
-# CHECK:      00000000 00000010 ffffffff CIE
+# CHECK:      00000000 00000010 00000000 CIE
 # CHECK-NEXT:   Version:               1
 # CHECK-NEXT:   Augmentation:          "zR"
 # CHECK-NEXT:   Code alignment factor: 1
 # CHECK-NEXT:   Data alignment factor: 1
 # CHECK-NEXT:   Return address column: 240
 # CHECK-NEXT:   Augmentation data:     1A
 
 .text

llvm/test/tools/llvm-objdump/eh_frame-arm64.test

 # RUN: llvm-objdump -dwarf=frames %p/Inputs/eh_frame.macho-arm64 2>/dev/null | FileCheck %s
 
 # CHECK: .eh_frame contents:
 
-# CHECK: 00000000 00000010 ffffffff CIE
+# CHECK: 00000000 00000010 00000000 CIE
 # CHECK:   Version:               1
 # CHECK:   Augmentation:          "zR"
 # CHECK:   Code alignment factor: 1
 # CHECK:   Data alignment factor: -8
 # CHECK:   Return address column: 30
 # CHECK:   Augmentation data:     10
 
 # CHECK:   DW_CFA_def_cfa: reg31 +0

llvm/test/tools/llvm-objdump/eh_frame-coff.test

 # RUN: yaml2obj %p/Inputs/eh_frame-coff.yaml | llvm-objdump -dwarf=frames - 2>/dev/null | FileCheck %s
 
 # CHECK: .eh_frame contents:
 
-# CHECK: 00000000 0000001c ffffffff CIE
+# CHECK: 00000000 0000001c 00000000 CIE
 # CHECK:   Version:               1
 # CHECK:   Augmentation:          "zPLR"
 # CHECK:   Code alignment factor: 1
 # CHECK:   Data alignment factor: -4
 # CHECK:   Return address column: 8
 # CHECK:   Personality Address: 00000000004025d7
 # CHECK:   Augmentation data:     00 D7 25 40 00 00 00
 

llvm/test/tools/llvm-objdump/eh_frame-mipsel.test

 # RUN: llvm-objdump -dwarf=frames %p/Inputs/eh_frame.elf-mipsel | FileCheck %s
 
 # CHECK: .eh_frame contents:
 
-# CHECK: 00000000 00000018 ffffffff CIE
+# CHECK: 00000000 00000018 00000000 CIE
 # CHECK:   Version:               1
 # CHECK:   Augmentation:          "zPLR"
 # CHECK:   Code alignment factor: 1
 # CHECK:   Data alignment factor: -4
 # CHECK:   Return address column: 31
 # CHECK:   Augmentation data:     80 90 0B 41 00 00 0B
 
 # CHECK:   DW_CFA_def_cfa: reg29 +0
 
 # CHECK: 0000001c 00000018 00000020 FDE cie=00000020 pc=00400890...004008dc
 # CHECK:   DW_CFA_advance_loc: 4
 # CHECK:   DW_CFA_def_cfa_offset: +24
 # CHECK:   DW_CFA_advance_loc: 4
 # CHECK:   DW_CFA_offset: reg31 -4
 # CHECK:   DW_CFA_nop:
 
-# CHECK: 00000038 00000000 ffffffff CIE
+# CHECK: 00000038 00000000 00000000 CIE
 # CHECK:   Version:               0
 # CHECK:   Augmentation:          ""
 # CHECK:   Code alignment factor: 0
 # CHECK:   Data alignment factor: 0
 # CHECK:   Return address column: 0

llvm/test/tools/llvm-objdump/eh_frame_zero_cie.test

 # RUN: llvm-objdump -dwarf=frames %p/Inputs/eh_frame_zero_cie.o 2>/dev/null | FileCheck %s
 
 # CHECK: .eh_frame contents:
 
-# CHECK: 00000000 00000000 ffffffff CIE
+# CHECK: 00000000 00000000 00000000 CIE
 # CHECK:   Version:               0
 # CHECK:   Augmentation:          ""
 # CHECK:   Code alignment factor: 0
 # CHECK:   Data alignment factor: 0
 # CHECK:   Return address column: 0