[llvm] [X86][MC] Add R_X86_64_CODE_4_GOTTPOFF (PR #116633)

[Feng Zou via llvm-commits]

https://github.com/fzou1 updated https://github.com/llvm/llvm-project/pull/116633

>From cbc4c61e9f53ac724f940c0a2ad3e86ca96ed446 Mon Sep 17 00:00:00 2001
From: Feng Zou <feng.zou at intel.com>
Date: Wed, 13 Nov 2024 10:43:33 +0800
Subject: [PATCH 1/2] [X86][MC] Add R_X86_64_CODE_4_GOTTPOFF

For

  mov name at GOTTPOFF(%rip), %reg
  add name at GOTTPOFF(%rip), %reg

add

  `R_X86_64_CODE_4_GOTTPOFF` = 44

if the instruction starts at 4 bytes before the relocation offset. It's similar
to R_X86_64_GOTTPOFF.

Linker can treat `R_X86_64_CODE_4_GOTTPOFF` as `R_X86_64_GOTTPOFF` or
convert the instructions above to

  mov $name at tpoff, %reg
  add $name at tpoff, %reg

if the first byte of the instruction at the relocation `offset - 4` is `0xd5`
(namely, encoded w/REX2 prefix) when possible.
---
 .../llvm/BinaryFormat/ELFRelocs/x86_64.def    |  1 +
 .../X86/MCTargetDesc/X86ELFObjectWriter.cpp   |  3 ++
 llvm/test/MC/X86/tls.s                        | 40 +++++++++++++++++++
 3 files changed, 44 insertions(+)
 create mode 100644 llvm/test/MC/X86/tls.s

diff --git a/llvm/include/llvm/BinaryFormat/ELFRelocs/x86_64.def b/llvm/include/llvm/BinaryFormat/ELFRelocs/x86_64.def
index 161b1969abfeb4..ff4516d1edf507 100644
--- a/llvm/include/llvm/BinaryFormat/ELFRelocs/x86_64.def
+++ b/llvm/include/llvm/BinaryFormat/ELFRelocs/x86_64.def
@@ -44,3 +44,4 @@ ELF_RELOC(R_X86_64_IRELATIVE,   37)
 ELF_RELOC(R_X86_64_GOTPCRELX,   41)
 ELF_RELOC(R_X86_64_REX_GOTPCRELX,    42)
 ELF_RELOC(R_X86_64_REX2_GOTPCRELX,    43)
+ELF_RELOC(R_X86_64_CODE_4_GOTTPOFF,    44)
\ No newline at end of file
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp
index 90222278d1ad6f..ab363e4eb8dce3 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp
@@ -197,6 +197,9 @@ static unsigned getRelocType64(MCContext &Ctx, SMLoc Loc,
     return ELF::R_X86_64_TLSGD;
   case MCSymbolRefExpr::VK_GOTTPOFF:
     checkIs32(Ctx, Loc, Type);
+    if ((unsigned)Kind == X86::reloc_riprel_4byte_movq_load_rex2 ||
+        (unsigned)Kind == X86::reloc_riprel_4byte_relax_rex2)
+      return ELF::R_X86_64_CODE_4_GOTTPOFF;
     return ELF::R_X86_64_GOTTPOFF;
   case MCSymbolRefExpr::VK_TLSLD:
     checkIs32(Ctx, Loc, Type);
diff --git a/llvm/test/MC/X86/tls.s b/llvm/test/MC/X86/tls.s
new file mode 100644
index 00000000000000..418ab692cac576
--- /dev/null
+++ b/llvm/test/MC/X86/tls.s
@@ -0,0 +1,40 @@
+// RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t
+// RUN: llvm-objdump -dr --no-print-imm-hex %t | FileCheck %s
+
+// CHECK:      <_start>:
+// CHECK-NEXT:   movq (%rip), %r16
+// CHECK-NEXT:   R_X86_64_CODE_4_GOTTPOFF    tls0-0x4
+// CHECK-NEXT:   movq (%rip), %r20
+// CHECK-NEXT:   R_X86_64_CODE_4_GOTTPOFF    tls0-0x4
+// CHECK-NEXT:   movq (%rip), %r16
+// CHECK-NEXT:   R_X86_64_CODE_4_GOTTPOFF    tls1-0x4
+// CHECK-NEXT:   addq (%rip), %r16
+// CHECK-NEXT:   R_X86_64_CODE_4_GOTTPOFF    tls0-0x4
+// CHECK-NEXT:   addq (%rip), %r28
+// CHECK-NEXT:   R_X86_64_CODE_4_GOTTPOFF    tls0-0x4
+// CHECK-NEXT:   addq (%rip), %r16
+// CHECK-NEXT:   R_X86_64_CODE_4_GOTTPOFF    tls1-0x4
+
+.type tls0, at object
+.section .tbss,"awT", at nobits
+.globl tls0
+.align 4
+tls0:
+.long 0
+.size tls0, 4
+.type  tls1, at object
+.globl tls1
+.align 4
+tls1:
+.long 0
+.size tls1, 4
+.section .text
+.globl _start
+_start:
+    # EGPR
+    movq tls0 at GOTTPOFF(%rip), %r16
+    movq tls0 at GOTTPOFF(%rip), %r20
+    movq tls1 at GOTTPOFF(%rip), %r16
+    addq tls0 at GOTTPOFF(%rip), %r16
+    addq tls0 at GOTTPOFF(%rip), %r28
+    addq tls1 at GOTTPOFF(%rip), %r16
\ No newline at end of file

>From 1dd700dca81210e4269976d2f5edafafb10d7351 Mon Sep 17 00:00:00 2001
From: Feng Zou <feng.zou at intel.com>
Date: Tue, 19 Nov 2024 15:14:37 +0800
Subject: [PATCH 2/2] Removed .align and .size in test, and added trailing
 '\n'.

---
 llvm/include/llvm/BinaryFormat/ELFRelocs/x86_64.def | 3 ++-
 llvm/test/MC/X86/tls.s                              | 7 ++-----
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/llvm/include/llvm/BinaryFormat/ELFRelocs/x86_64.def b/llvm/include/llvm/BinaryFormat/ELFRelocs/x86_64.def
index ff4516d1edf507..f3ce19e161fda3 100644
--- a/llvm/include/llvm/BinaryFormat/ELFRelocs/x86_64.def
+++ b/llvm/include/llvm/BinaryFormat/ELFRelocs/x86_64.def
@@ -44,4 +44,5 @@ ELF_RELOC(R_X86_64_IRELATIVE,   37)
 ELF_RELOC(R_X86_64_GOTPCRELX,   41)
 ELF_RELOC(R_X86_64_REX_GOTPCRELX,    42)
 ELF_RELOC(R_X86_64_REX2_GOTPCRELX,    43)
-ELF_RELOC(R_X86_64_CODE_4_GOTTPOFF,    44)
\ No newline at end of file
+ELF_RELOC(R_X86_64_CODE_4_GOTTPOFF,    44)
+
diff --git a/llvm/test/MC/X86/tls.s b/llvm/test/MC/X86/tls.s
index 418ab692cac576..2e3c16131a9836 100644
--- a/llvm/test/MC/X86/tls.s
+++ b/llvm/test/MC/X86/tls.s
@@ -18,16 +18,12 @@
 .type tls0, at object
 .section .tbss,"awT", at nobits
 .globl tls0
-.align 4
 tls0:
 .long 0
-.size tls0, 4
 .type  tls1, at object
 .globl tls1
-.align 4
 tls1:
 .long 0
-.size tls1, 4
 .section .text
 .globl _start
 _start:
@@ -37,4 +33,5 @@ _start:
     movq tls1 at GOTTPOFF(%rip), %r16
     addq tls0 at GOTTPOFF(%rip), %r16
     addq tls0 at GOTTPOFF(%rip), %r28
-    addq tls1 at GOTTPOFF(%rip), %r16
\ No newline at end of file
+    addq tls1 at GOTTPOFF(%rip), %r16
+