[llvm-branch-commits] [lld] [PAC][lld][AArch64][ELF] Support signed GOT with tiny code model (PR #113816)

[Fangrui Song via llvm-branch-commits]

================
@@ -78,6 +78,79 @@ _start:
   adrp x1, :got_auth:zed
   add  x1, x1, :got_auth_lo12:zed
 
+#--- ok-tiny.s
+
+# RUN: llvm-mc -filetype=obj -triple=aarch64-none-linux ok-tiny.s -o ok-tiny.o
+
+# RUN: ld.lld ok-tiny.o a.so -pie -o external-tiny
+# RUN: llvm-readelf -r -S -x .got external-tiny | FileCheck %s --check-prefix=EXTERNAL-TINY
+
+# RUN: ld.lld ok-tiny.o a.o -pie -o local-tiny
+# RUN: llvm-readelf -r -S -x .got -s local-tiny | FileCheck %s --check-prefix=LOCAL-TINY
+
+# EXTERNAL-TINY:      Offset            Info             Type                    Symbol's Value   Symbol's Name + Addend
+# EXTERNAL-TINY-NEXT: 0000000000020380  000000010000e201 R_AARCH64_AUTH_GLOB_DAT 0000000000000000 bar + 0
+# EXTERNAL-TINY-NEXT: 0000000000020388  000000020000e201 R_AARCH64_AUTH_GLOB_DAT 0000000000000000 zed + 0
+
+## Symbol's values for bar and zed are equal since they contain no content (see Inputs/shared.s)
+# LOCAL-TINY:         Offset            Info             Type                    Symbol's Value   Symbol's Name + Addend
+# LOCAL-TINY-NEXT:    0000000000020320  0000000000000411 R_AARCH64_AUTH_RELATIVE 10260
+# LOCAL-TINY-NEXT:    0000000000020328  0000000000000411 R_AARCH64_AUTH_RELATIVE 10260
+
+# EXTERNAL-TINY:      Hex dump of section '.got':
+# EXTERNAL-TINY-NEXT: 0x00020380 00000000 00000080 00000000 000000a0
+##                                              ^^
+##                                              0b10000000 bit 63 address diversity = true, bits 61..60 key = IA
+##                                                                ^^
+##                                                                0b10100000 bit 63 address diversity = true, bits 61..60 key = DA
+
+# LOCAL-TINY: Symbol table '.symtab' contains {{.*}} entries:
+# LOCAL-TINY:    Num:    Value          Size Type    Bind   Vis       Ndx Name
+# LOCAL-TINY:         0000000000010260     0 FUNC    GLOBAL DEFAULT     6 bar
+# LOCAL-TINY:         0000000000010260     0 NOTYPE  GLOBAL DEFAULT     6 zed
+
+# LOCAL-TINY:         Hex dump of section '.got':
+# LOCAL-TINY-NEXT:    0x00020320 00000000 00000080 00000000 000000a0
+##                                              ^^
+##                                              0b10000000 bit 63 address diversity = true, bits 61..60 key = IA
+##                                                                ^^
+##                                                                0b10100000 bit 63 address diversity = true, bits 61..60 key = DA
+
+# RUN: llvm-objdump -d external-tiny | FileCheck %s --check-prefix=EXTERNAL-TINY-ASM
+
+# EXTERNAL-TINY-ASM:      <_start>:
+# EXTERNAL-TINY-ASM-NEXT: adr x0, 0x20380
+# EXTERNAL-TINY-ASM-NEXT: ldr x1, [x0]
+# EXTERNAL-TINY-ASM-NEXT: adr x0, 0x20380
+# EXTERNAL-TINY-ASM-NEXT: ldr x1, 0x20380
+# EXTERNAL-TINY-ASM-NEXT: adr x0, 0x20388
+# EXTERNAL-TINY-ASM-NEXT: ldr x1, [x0]
+# EXTERNAL-TINY-ASM-NEXT: adr x0, 0x20388
+# EXTERNAL-TINY-ASM-NEXT: ldr x1, 0x20388
+
+# RUN: llvm-objdump -d local-tiny | FileCheck %s --check-prefix=LOCAL-TINY-ASM
+
+# LOCAL-TINY-ASM:         <_start>:
+# LOCAL-TINY-ASM-NEXT:    adr x0, 0x20320
+# LOCAL-TINY-ASM-NEXT:    ldr x1, [x0]
+# LOCAL-TINY-ASM-NEXT:    adr x0, 0x20320
+# LOCAL-TINY-ASM-NEXT:    ldr x1, 0x20320
+# LOCAL-TINY-ASM-NEXT:    adr x0, 0x20328
+# LOCAL-TINY-ASM-NEXT:    ldr x1, [x0]
+# LOCAL-TINY-ASM-NEXT:    adr x0, 0x20328
+# LOCAL-TINY-ASM-NEXT:    ldr x1, 0x20328
+
+.globl _start
+_start:
+  adr  x0, :got_auth:bar
----------------
MaskRay wrote:

No need for so many instructions.

We want very few instructions that look like simplified real-world codegen. While it's important to test two symbols to add some nuance, we can simplify the code here. Perhaps we just need

```
adr x0, :got_auth:bar
ldr x1, :got_auth:zed
```

https://github.com/llvm/llvm-project/pull/113816