[RelocationResolver] Add R_RISCV_SET8

[tschuett]

llvm/lib/Object/RelocationResolver.cpp

468

Is the 0x00 a typo or for symmetry?

[liaolucy]

update

[MaskRay]

Is there a test using this relocation type? We don't add unneeded ones.

llvm/lib/Object/RelocationResolver.cpp

468

& 0xff is needed

[liaolucy]

reserve 0xff.

[liaolucy]

In D134164#3800198, @MaskRay wrote:

Is there a test using this relocation type? We don't add unneeded ones.

Sorry, I can't find a .ll file to emit R_RISCV_SET8. Any suggestions?

https://github.com/llvm/llvm-project/blob/main/llvm/test/DebugInfo/RISCV/relax-debug-frame.ll emits R_RISCV_SET6, If R_RISCV_SET6 is not included in RelocationResolver.cpp, llvm-dwarfdump has the following error. I guess R_RISCV_SET8 may have a similar error.

warning: failed to compute relocation: R_RISCV_SET6, Invalid data was encountered while parsing the file

In addition, this question comes from Julia(like: https://github.com/JuliaLang/julia/issues/35460) @alexfanqi is helping to find testcases.

llvm/lib/Object/RelocationResolver.cpp

468

Thanks, updated

[liaolucy]

add testcase

[MaskRay]

llvm/test/MC/RISCV/cfi-advance.s

7

ditto nearby

8

The negative pattern is not needed. The no-error state is implied by llvm-dwarfdump rather than not llvm-dwarfdump

You may change llvm-dwarfdump --debug-info --debug-line to test some properties to best leverage the test (https://maskray.me/blog/2021-08-08-toolchain-testing "A regression test which simply runs the compiler and expects it not to crash has low utilization. It is often better to additionally test some properties of the produced object file.")

[liaolucy]

address comments.

llvm/lib/Object/RelocationResolver.cpp

 
 static bool supportsRISCV(uint64_t Type) {
   switch (Type) {
   case ELF::R_RISCV_NONE:
   case ELF::R_RISCV_32:
   case ELF::R_RISCV_32_PCREL:
   case ELF::R_RISCV_64:
   case ELF::R_RISCV_SET6:
+  case ELF::R_RISCV_SET8:
   case ELF::R_RISCV_SUB6:
   case ELF::R_RISCV_ADD8:
   case ELF::R_RISCV_SUB8:
   case ELF::R_RISCV_ADD16:
   case ELF::R_RISCV_SUB16:
   case ELF::R_RISCV_ADD32:
   case ELF::R_RISCV_SUB32:
   case ELF::R_RISCV_ADD64:
case ELF::R_RISCV_32:
     return (S + RA) & 0xFFFFFFFF;
   case ELF::R_RISCV_32_PCREL:
     return (S + RA - Offset) & 0xFFFFFFFF;
   case ELF::R_RISCV_64:
     return S + RA;
   case ELF::R_RISCV_SET6:
     return (A & 0xC0) | ((S + RA) & 0x3F);
   case ELF::R_RISCV_SUB6:
     return (A & 0xC0) | (((A & 0x3F) - (S + RA)) & 0x3F);
+  case ELF::R_RISCV_SET8:
+    return (S + RA) & 0xFF;
   case ELF::R_RISCV_ADD8:
     return (A + (S + RA)) & 0xFF;
   case ELF::R_RISCV_SUB8:
     return (A - (S + RA)) & 0xFF;
   case ELF::R_RISCV_ADD16:
     return (A + (S + RA)) & 0xFFFF;
   case ELF::R_RISCV_SUB16:
     return (A - (S + RA)) & 0xFFFF;

llvm/test/MC/RISCV/cfi-advance.s

+# RUN: llvm-mc -filetype=obj -triple riscv32 %s -o %t.o  
+# RUN: llvm-readobj -r %t.o | FileCheck -check-prefix=CHECK %s
+# RUN: llvm-dwarfdump --debug-frame %t.o 2>&1 \
+# RUN:     | FileCheck -check-prefix=CHECK-DWARFDUMP %s
+
+# CHECK: 0x26 R_RISCV_SET8 - 0x0
+# CHECK-DWARFDUMP:   DW_CFA_advance_loc1
+# CHECK-DWARFDUMP-NEXT:  DW_CFA_def_cfa_offset
+        .text
+        .globl  test                            # -- Begin function test
+        .p2align        1
+        .type   test,@function
+test:
+        .cfi_startproc
+        nop
+        .zero 100, 0x90
+        .cfi_def_cfa_offset 8
+        nop
+        .cfi_endproc