[PATCH] D92294: [X86] Support modifier @PLTOFF for R_X86_64_PLTOFF64

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
MaskRay added reviewers: grimar, craig.topper, RKSimon.
Herald added subscribers: llvm-commits, pengfei, steven_wu, hiraditya, inglorion.
Herald added a project: LLVM.
MaskRay requested review of this revision.

`gcc -mcmodel=large` can emit @PLTOFF.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D92294

Files:
  llvm/include/llvm/MC/MCExpr.h
  llvm/lib/MC/MCExpr.cpp
  llvm/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp
  llvm/test/MC/X86/pltoff.s


Index: llvm/test/MC/X86/pltoff.s
===================================================================
--- /dev/null
+++ llvm/test/MC/X86/pltoff.s
@@ -0,0 +1,16 @@
+# RUN: llvm-mc -triple=x86_64 %s | FileCheck %s --check-prefix=ASM
+# RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t
+# RUN: llvm-objdump -d -r %t | FileCheck %s --check-prefix=OBJ
+
+# RUN: not llvm-mc -filetype=obj -triple=x86_64 --defsym ERR=1 %s -o /dev/null 2>&1 | FileCheck %s --check-prefix=ERR
+
+# ASM:      movabsq $puts at PLTOFF, %rax
+# OBJ:      movabsq $0, %rax
+# OBJ-NEXT:   0000000000000002: R_X86_64_PLTOFF64 puts{{$}}
+
+movabsq $puts at PLTOFF, %rax
+
+.ifdef ERR
+# ERR: {{.*}}.s:[[#@LINE+1]]:1: error: 64 bit reloc applied to a field with a different size
+movl $puts at PLTOFF, %eax
+.endif
Index: llvm/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp
===================================================================
--- llvm/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp
+++ llvm/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp
@@ -94,6 +94,12 @@
                     "32 bit reloc applied to a field with a different size");
 }
 
+static void checkIs64(MCContext &Ctx, SMLoc Loc, X86_64RelType Type) {
+  if (Type != RT64_64)
+    Ctx.reportError(Loc,
+                    "64 bit reloc applied to a field with a different size");
+}
+
 static unsigned getRelocType64(MCContext &Ctx, SMLoc Loc,
                                MCSymbolRefExpr::VariantKind Modifier,
                                X86_64RelType Type, bool IsPCRel,
@@ -212,6 +218,9 @@
       return ELF::R_X86_64_REX_GOTPCRELX;
     }
     llvm_unreachable("unexpected relocation type!");
+  case MCSymbolRefExpr::VK_X86_PLTOFF:
+    checkIs64(Ctx, Loc, Type);
+    return ELF::R_X86_64_PLTOFF64;
   }
 }
 
Index: llvm/lib/MC/MCExpr.cpp
===================================================================
--- llvm/lib/MC/MCExpr.cpp
+++ llvm/lib/MC/MCExpr.cpp
@@ -253,6 +253,7 @@
   case VK_SIZE: return "SIZE";
   case VK_WEAKREF: return "WEAKREF";
   case VK_X86_ABS8: return "ABS8";
+  case VK_X86_PLTOFF: return "PLTOFF";
   case VK_ARM_NONE: return "none";
   case VK_ARM_GOT_PREL: return "GOT_PREL";
   case VK_ARM_TARGET1: return "target1";
@@ -410,6 +411,7 @@
     .Case("secrel32", VK_SECREL)
     .Case("size", VK_SIZE)
     .Case("abs8", VK_X86_ABS8)
+    .Case("pltoff", VK_X86_PLTOFF)
     .Case("l", VK_PPC_LO)
     .Case("h", VK_PPC_HI)
     .Case("ha", VK_PPC_HA)
Index: llvm/include/llvm/MC/MCExpr.h
===================================================================
--- llvm/include/llvm/MC/MCExpr.h
+++ llvm/include/llvm/MC/MCExpr.h
@@ -224,6 +224,7 @@
     VK_WEAKREF, // The link between the symbols in .weakref foo, bar
 
     VK_X86_ABS8,
+    VK_X86_PLTOFF,
 
     VK_ARM_NONE,
     VK_ARM_GOT_PREL,


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