[llvm] [LoongArch] Support R_LARCH_{ADD, SUB}_ULEB128 for .uleb128 and force relocs when sym is not in section (PR #76433)

[Lu Weining via llvm-commits]

================
@@ -0,0 +1,65 @@
+# RUN: llvm-mc --filetype=obj --triple=loongarch64 --mattr=-relax %s -o %t
+# RUN: llvm-readobj -r -x .alloc_w %t | FileCheck --check-prefixes=CHECK,NORELAX %s
+# RUN: llvm-mc --filetype=obj --triple=loongarch64 --mattr=+relax %s -o %t.relax
+# RUN: llvm-readobj -r -x .alloc_w %t.relax | FileCheck --check-prefixes=CHECK,RELAX %s
+
+# RUN: not llvm-mc --filetype=obj --triple=loongarch64 --mattr=-relax --defsym ERR=1 %s -o /dev/null 2>&1 | \
+# RUN:   FileCheck %s --check-prefix=ERR
+# RUN: not llvm-mc --filetype=obj --triple=loongarch64 --mattr=+relax --defsym ERR=1 %s -o /dev/null 2>&1 | \
+# RUN:   FileCheck %s --check-prefix=ERR
+
+# CHECK:      Relocations [
+# CHECK-NEXT:   .rela.alloc_w {
+# RELAX-NEXT:      0x0 R_LARCH_ADD_ULEB128 w1 0x0
+# RELAX-NEXT:      0x0 R_LARCH_SUB_ULEB128 w 0x0
+# RELAX-NEXT:      0x1 R_LARCH_ADD_ULEB128 w2 0x0
+# RELAX-NEXT:      0x1 R_LARCH_SUB_ULEB128 w1 0x0
+# CHECK-NEXT:      0x2 R_LARCH_PCALA_HI20 foo 0x0
+# RELAX-NEXT:      0x2 R_LARCH_RELAX - 0x0
+# CHECK-NEXT:      0x6 R_LARCH_PCALA_LO12 foo 0x0
+# RELAX-NEXT:      0x6 R_LARCH_RELAX - 0x0
+# RELAX-NEXT:      0xA R_LARCH_ADD_ULEB128 w2 0x0
+# RELAX-NEXT:      0xA R_LARCH_SUB_ULEB128 w1 0x0
+# RELAX-NEXT:      0xB R_LARCH_ADD_ULEB128 w2 0x78
+# RELAX-NEXT:      0xB R_LARCH_SUB_ULEB128 w1 0x0
+# RELAX-NEXT:      0xD R_LARCH_ADD_ULEB128 w1 0x0
+# RELAX-NEXT:      0xD R_LARCH_SUB_ULEB128 w2 0x0
+# CHECK-NEXT:   }
+# CHECK-NEXT: ]
+
+# CHECK:        Hex dump of section '.alloc_w':
+# NORELAX-NEXT: 0x00000000 00080c00 001a8c01 c0020880 01f8ffff
----------------
SixWeining wrote:

Should the first byte be `02`?

https://github.com/llvm/llvm-project/pull/76433