Be less aggressive at relaxing got access in this case.

This fixes pr30803 by not relaxing that particular access. We could
also let adjustRelaxExpr know that the target is absolute so that it
uses R_RELAX_GOT_PC_NOPIC, but it is not clear if it is worth it.

llvm-svn: 285317

diff --git a/lld/ELF/Relocations.cpp b/lld/ELF/Relocations.cpp
index 875871b..e5dc0c4 100644 (file)
--- a/lld/ELF/Relocations.cpp
+++ b/lld/ELF/Relocations.cpp
@@ -286,6 +286,10 @@ template <class ELFT> static bool isAbsolute(const SymbolBody &Body) {
   return false;
 }
 
+template <class ELFT> static bool isAbsoluteValue(const SymbolBody &Body) {
+  return isAbsolute<ELFT>(Body) || Body.isTls();
+}
+
 static bool needsPlt(RelExpr Expr) {
   return Expr == R_PLT_PC || Expr == R_PPC_PLT_OPD || Expr == R_PLT ||
          Expr == R_PLT_PAGE_PC || Expr == R_THUNK_PLT_PC;
@@ -322,7 +326,7 @@ static bool isStaticLinkTimeConstant(RelExpr E, uint32_t Type,
   if (!Config->Pic)
     return true;
 
-  bool AbsVal = isAbsolute<ELFT>(Body) || Body.isTls();
+  bool AbsVal = isAbsoluteValue<ELFT>(Body);
   bool RelE = isRelExpr(E);
   if (AbsVal && !RelE)
     return true;
@@ -433,7 +437,7 @@ static RelExpr adjustExpr(const elf::ObjectFile<ELFT> &File, SymbolBody &Body,
   } else if (!Preemptible) {
     if (needsPlt(Expr))
       Expr = fromPlt(Expr);
-    if (Expr == R_GOT_PC)
+    if (Expr == R_GOT_PC && !isAbsoluteValue<ELFT>(Body))
       Expr = Target->adjustRelaxExpr(Type, Data, Expr);
   }
   Expr = Target->getThunkExpr(Expr, Type, File, Body);

diff --git a/lld/test/ELF/x86-64-relax-got-abs.s b/lld/test/ELF/x86-64-relax-got-abs.s
new file mode 100644 (file)
index 0000000..c429120
--- /dev/null
+++ b/lld/test/ELF/x86-64-relax-got-abs.s
@@ -0,0 +1,16 @@
+// REQUIRES: x86
+// RUN: llvm-mc -filetype=obj -relax-relocations -triple=x86_64-pc-linux %s \
+// RUN:   -o %t.o
+// RUN: ld.lld %t.o -o %t.so -shared
+// RUN: llvm-objdump -d %t.so | FileCheck %s
+
+// We used to fail trying to relax this into a pc relocation to an absolute
+// value.
+
+// CHECK: movq  4185(%rip), %rax
+
+       movq    bar@GOTPCREL(%rip), %rax
+        .data
+        .global bar
+        .hidden bar
+        bar = 42