[PATCH] D47507: [MC] [X86] Teach leaq _GLOBAL_OFFSET_TABLE(%rip), %r15 to use R_X86_64_GOTPC32 instead of R_X86_64_PC32

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
Herald added a reviewer: javed.absar.
Herald added subscribers: llvm-commits, kristof.beyls.

This is similar to https://reviews.llvm.org/D46319 (ARM). x86-64 psABI p40 gives an example:

  leaq _GLOBAL_OFFSET_TABLE(%rip), %r15 # GOTPC32 reloc

GNU as creates such R_X86_64_GOTPC32. However, MC currently emits R_X86_64_PC32.


Repository:
  rL LLVM

https://reviews.llvm.org/D47507

Files:
  lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp


Index: lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
===================================================================
--- lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
+++ lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
@@ -350,8 +350,11 @@
       FixupKind == MCFixupKind(X86::reloc_riprel_4byte_movq_load) ||
       FixupKind == MCFixupKind(X86::reloc_riprel_4byte_relax) ||
       FixupKind == MCFixupKind(X86::reloc_riprel_4byte_relax_rex) ||
-      FixupKind == MCFixupKind(X86::reloc_branch_4byte_pcrel))
+      FixupKind == MCFixupKind(X86::reloc_branch_4byte_pcrel)) {
     ImmOffset -= 4;
+    if (StartsWithGlobalOffsetTable(Expr) != GOT_None)
+      FixupKind = MCFixupKind(X86::reloc_global_offset_table);
+  }
   if (FixupKind == FK_PCRel_2)
     ImmOffset -= 2;
   if (FixupKind == FK_PCRel_1)


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