[lld] [lld][ELF][AArch64] Support `R_AARCH64_GOT_LD_PREL19` relocation (PR #89592)

[Daniil Kovalev via llvm-commits]

https://github.com/kovdan01 created https://github.com/llvm/llvm-project/pull/89592

With tiny code model, the GOT slot contents can be loaded via `ldr x0, :got:sym` which corresponds to `R_AARCH64_GOT_LD_PREL19` static GOT-relative relocation.

See https://github.com/ARM-software/abi-aa/blob/main/aaelf64/aaelf64.rst#static-aarch64-relocations

>From 497c7d583fd718d6355bd85826d394f0a700624b Mon Sep 17 00:00:00 2001
From: Daniil Kovalev <dkovalev at accesssoftek.com>
Date: Mon, 22 Apr 2024 13:20:24 +0300
Subject: [PATCH] [lld][ELF][AArch64] Support `R_AARCH64_GOT_LD_PREL19`
 relocation

With tiny code model, the GOT slot contents can be loaded via
`ldr x0, :got:sym` which corresponds to `R_AARCH64_GOT_LD_PREL19` static
GOT-relative relocation.

See https://github.com/ARM-software/abi-aa/blob/main/aaelf64/aaelf64.rst#static-aarch64-relocations
---
 lld/ELF/Arch/AArch64.cpp        |  2 ++
 lld/test/ELF/aarch64-fpic-got.s | 42 +++++++++++++++++++++++----------
 2 files changed, 32 insertions(+), 12 deletions(-)

diff --git a/lld/ELF/Arch/AArch64.cpp b/lld/ELF/Arch/AArch64.cpp
index 2bf6e2c6c85195..47e6ea1ff77564 100644
--- a/lld/ELF/Arch/AArch64.cpp
+++ b/lld/ELF/Arch/AArch64.cpp
@@ -175,6 +175,7 @@ RelExpr AArch64::getRelExpr(RelType type, const Symbol &s,
   case R_AARCH64_TLSIE_ADR_GOTTPREL_PAGE21:
     return R_AARCH64_GOT_PAGE_PC;
   case R_AARCH64_GOTPCREL32:
+  case R_AARCH64_GOT_LD_PREL19:
     return R_GOT_PC;
   case R_AARCH64_NONE:
     return R_NONE;
@@ -460,6 +461,7 @@ void AArch64::relocate(uint8_t *loc, const Relocation &rel,
     break;
   case R_AARCH64_CONDBR19:
   case R_AARCH64_LD_PREL_LO19:
+  case R_AARCH64_GOT_LD_PREL19:
     checkAlignment(loc, val, 4, rel);
     checkInt(loc, val, 21, rel);
     or32le(loc, (val & 0x1FFFFC) << 3);
diff --git a/lld/test/ELF/aarch64-fpic-got.s b/lld/test/ELF/aarch64-fpic-got.s
index 48bd0e2be50958..db9900d604f1d1 100644
--- a/lld/test/ELF/aarch64-fpic-got.s
+++ b/lld/test/ELF/aarch64-fpic-got.s
@@ -1,26 +1,44 @@
 # REQUIRES: aarch64
 
-# RUN: llvm-mc -filetype=obj -triple=aarch64-none-linux %s -o %t.o
-# RUN: llvm-mc -filetype=obj -triple=aarch64-none-linux %p/Inputs/shared.s -o %t-lib.o
-# RUN: ld.lld -shared %t-lib.o -soname t-lib.so -o %t-lib.so
+# RUN: rm -rf %t && split-file %s %t && cd %t
 
-# RUN: ld.lld %t-lib.so %t.o -o %t.exe
-# RUN: llvm-readobj -r %t.exe | FileCheck --check-prefix=RELOC %s
-# RUN: llvm-objdump --no-print-imm-hex -d --no-show-raw-insn %t.exe | FileCheck --check-prefix=DIS %s
+# RUN: llvm-mc -filetype=obj -triple=aarch64-none-linux %p/Inputs/shared.s -o lib.o
+# RUN: ld.lld -shared lib.o -soname lib.so -o lib.so
 
 ## Checks if got access to dynamic objects is done through a got relative
 ## dynamic relocation and not using plt relative (R_AARCH64_JUMP_SLOT).
 # RELOC:      .rela.dyn {
-# RELOC-NEXT:   0x220320 R_AARCH64_GLOB_DAT bar 0x0
+# RELOC-NEXT:   0x220318 R_AARCH64_GLOB_DAT bar 0x0
 # RELOC-NEXT: }
 
-## page(0x220320) - page(0x210000) = 65536
-## page(0x220320) & 0xff8 = 800
-# DIS:      <_start>:
-# DIS-NEXT: 210258: adrp x0, 0x220000
-# DIS-NEXT: 21025c: ldr x0, [x0, #800]
+#--- small.s
+
+# RUN: llvm-mc -filetype=obj -triple=aarch64-none-linux small.s -o small.o
+# RUN: ld.lld lib.so small.o -o small.exe
+# RUN: llvm-readobj -r small.exe | FileCheck --check-prefix=RELOC %s
+# RUN: llvm-objdump --no-print-imm-hex -d --no-show-raw-insn small.exe | FileCheck --check-prefix=DIS-SMALL %s
+
+## page(0x220318) - page(0x210000) = 65536
+## page(0x220318) & 0xff8 = 792
+# DIS-SMALL:      <_start>:
+# DIS-SMALL-NEXT: 210250: adrp x0, 0x220000
+# DIS-SMALL-NEXT: 210254: ldr x0, [x0, #792]
 
 .globl _start
 _start:
   adrp x0, :got:bar
   ldr  x0, [x0, :got_lo12:bar]
+
+#--- tiny.s
+
+# RUN: llvm-mc -filetype=obj -triple=aarch64-none-linux tiny.s -o tiny.o
+# RUN: ld.lld lib.so tiny.o -o tiny.exe
+# RUN: llvm-readobj -r tiny.exe | FileCheck --check-prefix=RELOC %s
+# RUN: llvm-objdump --no-print-imm-hex -d --no-show-raw-insn tiny.exe | FileCheck --check-prefix=DIS-TINY %s
+
+# DIS-TINY:      <_start>:
+# DIS-TINY-NEXT: 210250: ldr x0, 0x220318
+
+.globl _start
+_start:
+  ldr  x0, :got:bar