[lld] [lld][LoongArch] GOT indirection to PC relative optimization (PR #123743)

[Lu Weining via llvm-commits]

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@@ -1261,6 +1314,22 @@ void LoongArch::relocateAlloc(InputSectionBase &sec, uint8_t *buf) const {
         tlsdescToLe(loc, rel, val);
       }
       continue;
+    case RE_LOONGARCH_GOT_PAGE_PC:
+      // In LoongArch, we try GOT indirection to PC relative optimization only
+      // when relaxation is enabled. This approach avoids determining whether
+      // relocation types are paired and whether the destination register of
+      // pcalau12i is only used by the immediately following instruction.
+      // Moreover, if the original code sequence can be relaxed to a single
+      // instruction `pcaddi`, the first instruction will be removed and it will
+      // not reach here.
+      if (isPairRelaxable(relocs, i) && rel.type == R_LARCH_GOT_PC_HI20 &&
----------------
SixWeining wrote:

- Check opcodes are exactly `pcalau12i + ld.{w,d}` in case the large code model (`pcalau12i + addi.d + lu32i.d + lu52i.d + ld.d`).
- Inline all these checks into `tryGotToPCRel`.

https://github.com/llvm/llvm-project/pull/123743