[lld] [lld] Merge equivalent symbols found during ICF (PR #134342)

[Fangrui Song via llvm-commits]

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+// REQUIRES: aarch64
+
+# RUN: llvm-mc -filetype=obj -triple=aarch64 %s -o %t
+# RUN: ld.lld %t -o %t2 --icf=all
+# RUN: llvm-objdump --section-headers %t2 | FileCheck %s --check-prefix=EXE
+
+# RUN: ld.lld -shared %t -o %t3 --icf=all
+# RUN: llvm-objdump --section-headers %t3 | FileCheck %s --check-prefix=DSO
+
+## All .rodata.* sections should merge into a single GOT entry
+# EXE: {{.*}}.got 00000008{{.*}}
+
+## When symbols are preemptible in DSO mode, GOT entries wouldn't be merged
+# DSO: {{.*}}.got 00000020{{.*}}
+
+.addrsig
+
+callee:
+ret
+
+.section .rodata.dummy1,"a", at progbits
+sym1:
+.long 111
+.long 122
+.byte 123
+
+.section .rodata.dummy2,"a", at progbits
+sym2:
+.long 111
+.long 122
+sym3:
+.byte 123
+
+.macro f, index
+
+# (Kept unique) first instruction of the GOT code sequence
+.section .text.f1_\index,"ax", at progbits
+f1_\index:
+adrp x0, :got:g\index
+mov x1, #\index
+b f2_\index
+
+# Folded, second instruction of the GOT code sequence
+.section .text.f2_\index,"ax", at progbits
+f2_\index:
+ldr x0, [x0, :got_lo12:g\index] 
+b callee
+
+# Folded
+.globl g\index
+.section .rodata.g\index,"a", at progbits
+g_\index:
+.long 111
+.long 122
+
+g\index:
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MaskRay wrote:

It seems that we need to duplicate the assembly to test the case when `g\index` symbols are local.

https://github.com/llvm/llvm-project/pull/134342