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

[Lu Weining via llvm-commits]

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+# REQUIRES: loongarch
+# RUN: rm -rf %t && split-file %s %t && cd %t
+
+# RUN: llvm-mc --filetype=obj --triple=loongarch64 a.s -o a.o
+# RUN: llvm-mc --filetype=obj --triple=loongarch64 unpaired.s -o unpaired.o
+# RUN: llvm-mc --filetype=obj --triple=loongarch64 lone-ldr.s -o lone-ldr.o
+
+# RUN: ld.lld a.o -T within-range.t -o a
+# RUN: llvm-objdump -d --no-show-raw-insn a | FileCheck %s
+
+## This test verifies the encoding when the register $a0 is used.
+# CHECK:      pcalau12i $a0, 0
+# CHECK-NEXT: addi.d    $a0, $a0, -2048
+
+## PCALAU12I contains a nonzero addend, no relaxations should be applied.
+# CHECK-NEXT: pcalau12i $a1, 2
+# CHECK-NEXT: ld.d      $a1, $a1, -2048
+
+## LD contains a nonzero addend, no relaxations should be applied.
+# CHECK-NEXT: pcalau12i $a2, 2
+# CHECK-NEXT: ld.d      $a2, $a2, -2040
+
+## PCALAU12I and LD use different registers, no relaxations should be applied.
+# CHECK-NEXT: pcalau12i $a3, 2
+# CHECK-NEXT: ld.d      $a4, $a3, -2048
+
+## PCALAU12I and LD use different registers, no relaxations should be applied.
+# CHECK-NEXT: pcalau12i $a5, 2
+# CHECK-NEXT: ld.d      $a5, $a6, -2048
+
+# RUN: ld.lld a.o -T underflow-range.t -o a
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SixWeining wrote:

```suggestion
# RUN: ld.lld a.o -T underflow-range.t -o a-underflow
```

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