[google gcc-4_8][x86_64]Optimize access to globals in "-fpie -pie" builds with copy relocations

[Sriraman Tallam]

This patch is pending review for trunk. Please see if this is ok to
commit to google/gcc-4_8 branch. Please see this for more details:

https://gcc.gnu.org/ml/gcc-patches/2014-05/msg01215.html

Patch attached.

Thanks
Sri

Index: config/i386/i386.c
===================================================================
--- config/i386/i386.c  (revision 210728)
+++ config/i386/i386.c  (working copy)
@@ -12540,7 +12540,10 @@ legitimate_pic_address_disp_p (rtx disp)
          /* TLS references should always be enclosed in UNSPEC.  */
          if (SYMBOL_REF_TLS_MODEL (op0))
            return false;
-         if (!SYMBOL_REF_FAR_ADDR_P (op0) && SYMBOL_REF_LOCAL_P (op0)
+         if (!SYMBOL_REF_FAR_ADDR_P (op0)
+             && (SYMBOL_REF_LOCAL_P (op0)
+                 || (TARGET_64BIT && ix86_ld_pie_copyrelocs && flag_pie
+                     && !SYMBOL_REF_FUNCTION_P (op0)))
              && ix86_cmodel != CM_LARGE_PIC)
            return true;
          break;
Index: config/i386/i386.opt
===================================================================
--- config/i386/i386.opt        (revision 210728)
+++ config/i386/i386.opt        (working copy)
@@ -198,6 +198,10 @@ mfancy-math-387
 Target RejectNegative Report InverseMask(NO_FANCY_MATH_387, 
USE_FANCY_MATH_387) Save
 Generate sin, cos, sqrt for FPU
 
+mld-pie-copyrelocs
+Target Report Var(ix86_ld_pie_copyrelocs) Init(0)
+Use linker copy relocs for pie
+
 mforce-drap
 Target Report Var(ix86_force_drap)
 Always use Dynamic Realigned Argument Pointer (DRAP) to realign stack
Index: testsuite/gcc.target/i386/ld-pie-copyrelocs-1.c
===================================================================
--- testsuite/gcc.target/i386/ld-pie-copyrelocs-1.c     (revision 0)
+++ testsuite/gcc.target/i386/ld-pie-copyrelocs-1.c     (revision 0)
@@ -0,0 +1,13 @@
+/* Test if -mld-pie-copyrelocs does the right thing. */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fpie -mld-pie-copyrelocs" } */
+
+extern int glob_a;
+
+int foo ()
+{
+  return glob_a;
+}
+
+/* glob_a should never be accessed with a GOTPCREL  */ 
+/* { dg-final { scan-assembler-not "glob_a\\@GOTPCREL" { target { x86_64-*-* } 
} } } */
Index: testsuite/gcc.target/i386/ld-pie-copyrelocs-2.c
===================================================================
--- testsuite/gcc.target/i386/ld-pie-copyrelocs-2.c     (revision 0)
+++ testsuite/gcc.target/i386/ld-pie-copyrelocs-2.c     (revision 0)
@@ -0,0 +1,13 @@
+/* Test if -mno-ld-pie-copyrelocs does the right thing. */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fpie -mno-ld-pie-copyrelocs" } */
+
+extern int glob_a;
+
+int foo ()
+{
+  return glob_a;
+}
+
+/* glob_a should always be accessed via GOT  */ 
+/* { dg-final { scan-assembler "glob_a\\@GOT" { target { x86_64-*-* } } } } */