[lld] [X86][LLD] Handle R_X86_64_CODE_6_GOTTPOFF relocation type (PR #117675)

[Shengchen Kan via llvm-commits]

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@@ -623,6 +625,32 @@ void X86_64::relaxTlsIeToLe(uint8_t *loc, const Relocation &rel,
                << "R_X86_64_CODE_4_GOTTPOFF must be used in MOVQ or ADDQ "
                   "instructions only";
     }
+  } else if (rel.type == R_X86_64_CODE_6_GOTTPOFF) {
+    if (loc[-6] != 0x62) {
+      Err(ctx) << getErrorLoc(ctx, loc - 6)
+               << "Invalid prefix with R_X86_64_CODE_6_GOTTPOFF!";
+      return;
+    }
+    if (loc[-2] == 0x3 || loc[-2] == 0x1) {
+      // "addq %reg1, foo at GOTTPOFF(%rip), %reg2" -> "addq $foo, %reg1, %reg2"
+      // "addq foo at GOTTPOFF(%rip), %reg1, %reg2" -> "addq $foo, %reg1, %reg2"
+      // "{nf} addq %reg1, foo at GOTTPOFF(%rip), %reg2"
+      //   -> "{nf} addq $foo, %reg1, %reg2"
+      // "{nf} addq name at GOTTPOFF(%rip), %reg1, %reg2"
+      //    -> "{nf} addq $foo, %reg1, %reg2"
+      // "{nf} addq name at GOTTPOFF(%rip), %reg" -> "{nf} addq $foo, %reg"
+      loc[-2] = 0x81;
+      // Move R bits to B bits in EVEX payloads and ModRM byte.
+      if ((loc[-5] & (1 << 7)) == 0)
+        loc[-5] = (loc[-5] | (1 << 7)) & ~(1 << 5);
+      if ((loc[-5] & (1 << 4)) == 0)
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KanRobert wrote:

Should we remove the if condition at line 644 and 646? 

https://github.com/llvm/llvm-project/pull/117675