Re: ping Dale's patches

[Andrew Pinski <pinskia at physics dot uc dot edu>]

On May 30, 2004, at 13:43, Roger Sayle wrote:
> > http://gcc.gnu.org/ml/gcc-patches/2004-04/msg01946.html
> > Patch: disable invalid REG_EQUAL note
>
> I think its best to explore the "very dusty twisty little
> passages of darwin-specific address generation".  I was
> going to approve this patch (with Andrews suggested change
> to use "== const0_rtx") when I realized that GCC's RTL
> canonicalization rules mean that the RTX "(MINUS X CONST_INT)"
> should never match!  So Darwin (or the RTL optimizers) should
> be generating addresses as (PLUS X -C) instead of (MINUS X C),
> in addition to the fact that we should obviously never see
> either (MINUS X 0) or (PLUS X 0).
>
> Do you have a test case, so that others can help investigate?

I do not have one but I think I have a patch which should make sure
that those RTL do not get created in the first place, they only happen
when dynamic-no-pic is turned on.
Tested and bootstrapped on powerpc-apple-darwin with no regressions.

Thanks,
Andrew Pinski

ChangeLog:
	* config/darwin.c (machopic_legitimize_pic_address): Set pic_base
	to NULL_RTX for dynamic-no-pic case.  Check for NULL pic_base and
	do not create RTL that reference const_zero.


Index: config/darwin.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/config/darwin.c,v
retrieving revision 1.68
diff -u -p -r1.68 darwin.c
--- config/darwin.c	29 May 2004 02:55:23 -0000	1.68
+++ config/darwin.c	30 May 2004 17:59:10 -0000
@@ -624,9 +624,9 @@ machopic_legitimize_pic_address (rtx ori

       /* if dynamic-no-pic then use 0 as the pic base  */
       if (MACHO_DYNAMIC_NO_PIC_P)
-	pic_base = CONST0_RTX (Pmode);
+	pic_base = NULL_RTX;
       else
-      pic_base = gen_rtx_SYMBOL_REF (Pmode, 
machopic_function_base_name ());
+        pic_base = gen_rtx_SYMBOL_REF (Pmode, 
machopic_function_base_name ());

       if (GET_CODE (orig) == MEM)
 	{
@@ -664,9 +664,10 @@ machopic_legitimize_pic_address (rtx ori
 	      || GET_CODE (XEXP (orig, 0)) == LABEL_REF)
 	    {
 	      rtx offset = gen_rtx_CONST (Pmode,
-					  gen_rtx_MINUS (Pmode,
-							 XEXP (orig, 0),
-							 pic_base));
+                                          pic_base == NULL_RTX ? XEXP 
(orig, 0) :
+					                         gen_rtx_MINUS (Pmode,
+						                 	        XEXP (orig, 0),
+							                        pic_base));
 #if defined (TARGET_TOC) /* i.e., PowerPC */
 	      /* Generating a new reg may expose opportunities for
 		 common subexpression elimination.  */
@@ -722,11 +723,13 @@ machopic_legitimize_pic_address (rtx ori
 #endif

 	      pic_ref = gen_rtx_PLUS (Pmode,
-				      pic,
+				      pic,
 				      gen_rtx_CONST (Pmode,
-					  gen_rtx_MINUS (Pmode,
-							 XEXP (orig, 0),
-							 pic_base)));
+                                                     pic_base == 
NULL_RTX
+                                                     ? XEXP (orig, 0) :
+					               gen_rtx_MINUS (Pmode,
+                                                                      
XEXP (orig, 0),
+                                                                      
pic_base)));
 	    }

 #if !defined (TARGET_TOC)
@@ -743,8 +746,10 @@ machopic_legitimize_pic_address (rtx ori
 	      || GET_CODE (orig) == LABEL_REF)
 	    {
 	      rtx offset = gen_rtx_CONST (Pmode,
-					  gen_rtx_MINUS (Pmode,
-							 orig, pic_base));
+                                   	  pic_base == NULL_RTX
+                                           ? orig:
+					     gen_rtx_MINUS (Pmode,
+							    orig, pic_base));
 #if defined (TARGET_TOC) /* i.e., PowerPC */
               rtx hi_sum_reg;

@@ -802,8 +807,11 @@ machopic_legitimize_pic_address (rtx ori
 		  pic_ref = gen_rtx_PLUS (Pmode,
 					  pic,
 					  gen_rtx_CONST (Pmode,
-					      gen_rtx_MINUS (Pmode,
-							     orig, pic_base)));
+                                                         pic_base == 
NULL_RTX
+                      					 ? orig
+                                                         :  
gen_rtx_MINUS (Pmode,
+							                   orig,
+                                                                       
    pic_base)));
 		}
 	    }
 	}