Patchwork PowerPC64 large toc model

login
register
mail settings
Submitter Alan Modra
Date Sept. 23, 2010, 11:26 a.m.
Message ID <20100923112640.GB16376@bubble.grove.modra.org>
Download mbox | patch
Permalink /patch/65528/
State New
Headers show

Comments

Alan Modra - Sept. 23, 2010, 11:26 a.m.
I'm a little embarassed to admit that the hack I put in with the aim
of better supporting non-fPIC shared libs on powerpc64 is almost
completely useless.  The thing is that -fsection-anchors, on by
default, results in non-fPIC shared libs that won't support overriding
of global vars anyway.  So there isn't much point in avoiding an
-mcmodel=medium optimisation.

Bootstrapped etc. powerpc64-linux, OK'd offline by David.

	* config/rs6000/rs6000.c (toc_relative_ok): Delete.
	(rs6000_emit_move): Use SYMBOL_REF_LOCAL_P instead.

Patch

Index: gcc/config/rs6000/rs6000.c
===================================================================
--- gcc/config/rs6000/rs6000.c	(revision 164538)
+++ gcc/config/rs6000/rs6000.c	(working copy)
@@ -7032,46 +7032,6 @@  rs6000_eliminate_indexed_memrefs (rtx op
 			       copy_addr_to_reg (XEXP (operands[1], 0)));
 }
 
-/* Return true if OP, a SYMBOL_REF, should be considered local when
-   generating -mcmodel=medium code.  */
-
-static bool
-toc_relative_ok (rtx op)
-{
-  tree decl;
-
-  if (!SYMBOL_REF_LOCAL_P (op))
-    return false;
-
-  /* This is a bit hard to explain.  When building shared libraries,
-     you are supposed to pass -fpic or -fPIC to the compiler.
-     -fpic/-fPIC not only generate position independent code but also
-     generate code that supports ELF shared library global function
-     or variable overriding.  ppc64 is always PIC and at least some of
-     the ELF shared libaray semantics of global variables happen to be
-     supported without -fpic/-fPIC.  So people may not be careful
-     about using -fPIC for shared libs.
-     With -mcmodel=medium this situation changes.  A shared library
-     built without -fpic/-fPIC requires text relocs for global var
-     access (and would fail to load since glibc ld.so doesn't support
-     the required dynamic relocs).  So avoid this potential
-     problem by using -mcmodel=large access for global vars, unless
-     we know we are compiling for an executable.  */
-  if (flag_pie)
-    return true;
-
-  decl = SYMBOL_REF_DECL (op);
-  if (!decl || !DECL_P (decl))
-    return true;
-  if (!TREE_PUBLIC (decl))
-    return true;
-  if (DECL_VISIBILITY (decl) != VISIBILITY_DEFAULT)
-    return true;
-
-  /* If we get here we must have a global var.  See binds_local_p.  */
-  return flag_whole_program;
-}
-
 /* Return true if memory accesses to DECL are known to never straddle
    a 32k boundary.  */
 
@@ -7427,7 +7387,7 @@  rs6000_emit_move (rtx dest, rtx source, 
 	  || (TARGET_CMODEL == CMODEL_MEDIUM
 	      && GET_CODE (operands[1]) == SYMBOL_REF
 	      && !CONSTANT_POOL_ADDRESS_P (operands[1])
-	      && toc_relative_ok (operands[1])
+	      && SYMBOL_REF_LOCAL_P (operands[1])
 	      && offsettable_ok_by_alignment (SYMBOL_REF_DECL (operands[1]))))
 	{
 	  rtx reg = NULL_RTX;