[lld][LoongArch] Support the R_LARCH_{ADD,SUB}6 relocation type

[MQ-mengqing]

The R_LARCH_{ADD,SUB}6 relocation type are usually used by DwarfCFA to calculate a tiny offset. They appear after binutils 2.41, with GAS enabling relaxation by default.

[llvmbot]

@llvm/pr-subscribers-lld

@llvm/pr-subscribers-lld-elf

Author: Jinyang He (MQ-mengqing)

Changes

The R_LARCH_{ADD,SUB}6 relocation type are usually used by DwarfCFA to calculate a tiny offset. They appear after binutils 2.41, with GAS enable relaxation by default.

---

Full diff: https://github.com/llvm/llvm-project/pull/72190.diff

2 Files Affected:

• (modified) lld/ELF/Arch/LoongArch.cpp (+8)
• (modified) lld/test/ELF/loongarch-add-sub.s (+5-1)

diff --git a/lld/ELF/Arch/LoongArch.cpp b/lld/ELF/Arch/LoongArch.cpp
index 04ddb4682917b4b..d3a538577a59a5d 100644
--- a/lld/ELF/Arch/LoongArch.cpp
+++ b/lld/ELF/Arch/LoongArch.cpp
@@ -444,10 +444,12 @@ RelExpr LoongArch::getRelExpr(const RelType type, const Symbol &s,
   case R_LARCH_TLS_LE64_LO20:
   case R_LARCH_TLS_LE64_HI12:
     return R_TPREL;
+  case R_LARCH_ADD6:
   case R_LARCH_ADD8:
   case R_LARCH_ADD16:
   case R_LARCH_ADD32:
   case R_LARCH_ADD64:
+  case R_LARCH_SUB6:
   case R_LARCH_SUB8:
   case R_LARCH_SUB16:
   case R_LARCH_SUB32:
@@ -650,6 +652,9 @@ void LoongArch::relocate(uint8_t *loc, const Relocation &rel,
     write32le(loc, setK12(read32le(loc), extractBits(val, 63, 52)));
     return;
 
+  case R_LARCH_ADD6:
+    *loc = (*loc & 0xc0) | ((*loc + val) & 0x3f);
+    return;
   case R_LARCH_ADD8:
     *loc += val;
     return;
@@ -662,6 +667,9 @@ void LoongArch::relocate(uint8_t *loc, const Relocation &rel,
   case R_LARCH_ADD64:
     write64le(loc, read64le(loc) + val);
     return;
+  case R_LARCH_SUB6:
+    *loc = (*loc & 0xc0) | ((*loc - val) & 0x3f);
+    return;
   case R_LARCH_SUB8:
     *loc -= val;
     return;
diff --git a/lld/test/ELF/loongarch-add-sub.s b/lld/test/ELF/loongarch-add-sub.s
index 63a3f7de179e6b8..35f8a053d69cef3 100644
--- a/lld/test/ELF/loongarch-add-sub.s
+++ b/lld/test/ELF/loongarch-add-sub.s
@@ -6,7 +6,7 @@
 # RUN: llvm-readelf -x .rodata %t.la64 | FileCheck --check-prefix=CHECK %s
 # CHECK:      section '.rodata':
 # CHECK-NEXT: 0x9876543210 10325476 98badcfe 804602be 79ffffff
-# CHECK-NEXT: 0x9876543220 804602be 804680
+# CHECK-NEXT: 0x9876543220 804602be 80468097
 
 .text
 .global _start
@@ -34,3 +34,7 @@ quux:
     .byte 0
     .reloc quux, R_LARCH_ADD8, 1b
     .reloc quux, R_LARCH_SUB8, 2b
+qux:
+    .byte 0b10000000
+    .reloc qux, R_LARCH_ADD6, qux
+    .reloc qux, R_LARCH_SUB6, 2b

[MQ-mengqing]

Add: @SixWeining @xen0n @xry111 .

[xen0n]

Thanks!

[MaskRay]

They appear after binutils 2.41, with GAS enable relaxation by default.

They appear after binutils 2.41, with GAS enabling relaxation by default.

[SixWeining]

Seems your email setting needs some changes. I see: [email protected]