[lld] r266425 - Don't create relocations for non preemptable absolute symbols.

[Rafael Espindola via llvm-commits]

Author: rafael
Date: Fri Apr 15 07:22:22 2016
New Revision: 266425

URL: http://llvm.org/viewvc/llvm-project?rev=266425&view=rev
Log:
Don't create relocations for non preemptable absolute symbols.

Added:
    lld/trunk/test/ELF/Inputs/abs-hidden.s
    lld/trunk/test/ELF/abs-hidden.s
Modified:
    lld/trunk/ELF/Writer.cpp

Modified: lld/trunk/ELF/Writer.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=266425&r1=266424&r2=266425&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.cpp (original)
+++ lld/trunk/ELF/Writer.cpp Fri Apr 15 07:22:22 2016
@@ -411,6 +411,16 @@ static int32_t findMipsPairedAddend(cons
   return 0;
 }
 
+// True if non-preemptable symbol always has the same value regardless of where
+// the DSO is loaded.
+template <class ELFT> static bool isAbsolute(const SymbolBody &Body) {
+  if (Body.isUndefined() && Body.isWeak())
+    return true; // always 0
+  if (const auto *DR = dyn_cast<DefinedRegular<ELFT>>(&Body))
+    return DR->Section == nullptr; // Absolute symbol.
+  return false;
+}
+
 // The reason we have to do this early scan is as follows
 // * To mmap the output file, we need to know the size
 // * For that, we need to know how many dynamic relocs we will have.
@@ -618,7 +628,7 @@ void Writer<ELFT>::scanRelocs(InputSecti
     // can process some of it and and just ask the dynamic linker to add the
     // load address.
     if (!Config->Pic || Target->isRelRelative(Type) || Expr == R_PC ||
-        Expr == R_SIZE || (Body.isUndefined() && Body.isWeak())) {
+        Expr == R_SIZE || isAbsolute<ELFT>(Body)) {
       if (Config->EMachine == EM_MIPS && Body.isLocal() &&
           (Type == R_MIPS_GPREL16 || Type == R_MIPS_GPREL32))
         Expr = R_MIPS_GP0;

Added: lld/trunk/test/ELF/Inputs/abs-hidden.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/Inputs/abs-hidden.s?rev=266425&view=auto
==============================================================================
--- lld/trunk/test/ELF/Inputs/abs-hidden.s (added)
+++ lld/trunk/test/ELF/Inputs/abs-hidden.s Fri Apr 15 07:22:22 2016
@@ -0,0 +1,3 @@
+.global foo
+.hidden foo
+foo = 0x42

Added: lld/trunk/test/ELF/abs-hidden.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/abs-hidden.s?rev=266425&view=auto
==============================================================================
--- lld/trunk/test/ELF/abs-hidden.s (added)
+++ lld/trunk/test/ELF/abs-hidden.s Fri Apr 15 07:22:22 2016
@@ -0,0 +1,27 @@
+// REQUIRES: x86
+// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %p/Inputs/abs-hidden.s -o %t2.o
+// RUN: ld.lld %t.o %t2.o -o %t.so -shared
+// RUN: llvm-readobj -r -s -section-data %t.so | FileCheck %s
+
+        .quad foo
+
+// CHECK:      Name: .text
+// CHECK-NEXT: Type: SHT_PROGBITS
+// CHECK-NEXT: Flags [
+// CHECK-NEXT:   SHF_ALLOC
+// CHECK-NEXT:   SHF_EXECINSTR
+// CHECK-NEXT: ]
+// CHECK-NEXT: Address:
+// CHECK-NEXT: Offset:
+// CHECK-NEXT: Size: 8
+// CHECK-NEXT: Link: 0
+// CHECK-NEXT: Info: 0
+// CHECK-NEXT: AddressAlignment: 4
+// CHECK-NEXT: EntrySize: 0
+// CHECK-NEXT: SectionData (
+// CHECK-NEXT:   0000: 42000000 00000000
+// CHECK-NEXT: )
+
+// CHECK:      Relocations [
+// CHECK-NEXT: ]