invoke.text: Reinstate mcmodel=medium.

* doc/invoke.text: Reinstate mcmodel=medium.
	* config/rs6000/linux64.h (SUBSUBTARGET_OVERRIDE_OPTIONS): Set
	CMODEL_MEDIUM as default.
	* config/rs6000/rs6000.h (enum rs6000_cmodel): Add CMODEL_MEDIUM.
	* config/rs6000/rs6000.c (rs6000_handle_option): Add mcmodel=medium.
	(toc_relative_ok, offsettable_ok_by_alignment): New functions.
	(rs6000_emit_move): Reinstate mcmodel=medium optimization.

From-SVN: r164045

gcc/ChangeLog

@@ -1,3 +1,13 @@
+2010-09-09  Alan Modra  <amodra@gmail.com>
+
+	* doc/invoke.text: Reinstate mcmodel=medium.
+	* config/rs6000/linux64.h (SUBSUBTARGET_OVERRIDE_OPTIONS): Set
+	CMODEL_MEDIUM as default.
+	* config/rs6000/rs6000.h (enum rs6000_cmodel): Add CMODEL_MEDIUM.
+	* config/rs6000/rs6000.c (rs6000_handle_option): Add mcmodel=medium.
+	(toc_relative_ok, offsettable_ok_by_alignment): New functions.
+	(rs6000_emit_move): Reinstate mcmodel=medium optimization.
+
 2010-09-08  John David Anglin  <dave.anglin@nrc-cnrc.gc.ca>
 
 	PR target/45250

gcc/config/rs6000/linux64.h

@@ -134,7 +134,7 @@ extern enum rs6000_cmodel cmodel;
 	  else							\
 	    {							\
 	      if (!rs6000_explicit_options.cmodel)		\
-		SET_CMODEL (CMODEL_LARGE);			\
+		SET_CMODEL (CMODEL_MEDIUM);			\
 	      if (cmodel != CMODEL_SMALL)			\
 		{						\
 		  TARGET_NO_FP_IN_TOC = 0;			\

gcc/config/rs6000/rs6000.c

@@ -6992,6 +6992,80 @@ rs6000_eliminate_indexed_memrefs (rtx operands[2])
 			       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.  */
+
+static bool
+offsettable_ok_by_alignment (tree decl)
+{
+  unsigned HOST_WIDE_INT dsize, dalign;
+
+  /* Presume any compiler generated symbol_ref is suitably aligned.  */
+  if (!decl)
+    return true;
+
+  if (TREE_CODE (decl) != VAR_DECL
+      && TREE_CODE (decl) != PARM_DECL
+      && TREE_CODE (decl) != RESULT_DECL
+      && TREE_CODE (decl) != FIELD_DECL)
+    return true;
+
+  if (!DECL_SIZE_UNIT (decl))
+    return false;
+
+  if (!host_integerp (DECL_SIZE_UNIT (decl), 1))
+    return false;
+
+  dsize = tree_low_cst (DECL_SIZE_UNIT (decl), 1);
+  if (dsize <= 1)
+    return true;
+  if (dsize > 32768)
+    return false;
+
+  dalign = DECL_ALIGN_UNIT (decl);
+  return dalign >= dsize;
+}
+
 /* Emit a move from SOURCE to DEST in mode MODE.  */
 void
 rs6000_emit_move (rtx dest, rtx source, enum machine_mode mode)
@@ -7305,11 +7379,16 @@ rs6000_emit_move (rtx dest, rtx source, enum machine_mode mode)
       /* If this is a SYMBOL_REF that refers to a constant pool entry,
 	 and we have put it in the TOC, we just need to make a TOC-relative
 	 reference to it.  */
-      if (TARGET_TOC
-	  && GET_CODE (operands[1]) == SYMBOL_REF
-	  && constant_pool_expr_p (operands[1])
-	  && ASM_OUTPUT_SPECIAL_POOL_ENTRY_P (get_pool_constant (operands[1]),
-					      get_pool_mode (operands[1])))
+      if ((TARGET_TOC
+	   && GET_CODE (operands[1]) == SYMBOL_REF
+	   && constant_pool_expr_p (operands[1])
+	   && ASM_OUTPUT_SPECIAL_POOL_ENTRY_P (get_pool_constant (operands[1]),
+					       get_pool_mode (operands[1])))
+	  || (TARGET_CMODEL == CMODEL_MEDIUM
+	      && GET_CODE (operands[1]) == SYMBOL_REF
+	      && !CONSTANT_POOL_ADDRESS_P (operands[1])
+	      && toc_relative_ok (operands[1])
+	      && offsettable_ok_by_alignment (SYMBOL_REF_DECL (operands[1]))))
 	{
 	  rtx reg = NULL_RTX;
 	  if (TARGET_CMODEL != CMODEL_SMALL)

gcc/config/rs6000/rs6000.h

@@ -297,9 +297,11 @@ extern const char *host_detect_local_cpu (int argc, const char **argv);
 
 /* Code model for 64-bit linux.
    small: 16-bit toc offsets.
-   large: 32-bit toc offsets.  */
+   medium: 32-bit toc offsets, static data and code within 2G of TOC pointer.
+   large: 32-bit toc offsets, no limit on static data and code.  */
 enum rs6000_cmodel {
   CMODEL_SMALL,
+  CMODEL_MEDIUM,
   CMODEL_LARGE
 };
 

gcc/doc/invoke.texi

@@ -15213,6 +15213,11 @@ scheduling parameters set by @option{-mtune}.
 Generate PowerPC64 code for the small model: The TOC is limited to
 64k.
 
+@item -mcmodel=medium
+@opindex mcmodel=medium
+Generate PowerPC64 code for the medium model: The TOC and other static
+data may be up to a total of 4G in size.
+
 @item -mcmodel=large
 @opindex mcmodel=large
 Generate PowerPC64 code for the large model: The TOC may be up to 4G