[lld] [lld][LoongArch] Support the R_LARCH_{ADD,SUB}_ULEB128 relocation types (PR #81133)

[Fangrui Song via llvm-commits]

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@@ -153,6 +154,23 @@ static bool isJirl(uint32_t insn) {
   return (insn & 0xfc000000) == JIRL;
 }
 
+static void handleUleb128(uint8_t *loc, uint64_t val) {
+  const char *err = nullptr;
+  const uint32_t maxcount = 1 + (config->is64 ? 64 : 32) / 7;
+  uint32_t count;
+  uint64_t orig = decodeULEB128(loc, &count, nullptr, &err);
+  if (err)
+    fatal(getErrorLocation(loc) + "could not decode uleb128 value: " + err);
+  if (count > maxcount)
+    errorOrWarn(getErrorLocation(loc) + "extra space for uleb128");
+  uint64_t mask = config->is64 ? -1 : -1u;
+  if (count < maxcount)
+    mask = (1 << 7 * count) - 1;
+
+  val = (orig + val) & mask;
+  encodeULEB128(val, loc, count);
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MaskRay wrote:

see `overwriteULEB128`

https://github.com/llvm/llvm-project/pull/81133