emit-rtl.c (gen_lowpart): When requesting the low-part of a MEM...

	* emit-rtl.c (gen_lowpart): When requesting the low-part of a
	MEM, try loading the MEM into a register and taking the low-part
	of that, to help CSE see the use of the MEM in its true mode.

From-SVN: r63907

gcc/ChangeLog

+2003-03-06  Roger Sayle  <roger@eyesopen.com>
+
+	* emit-rtl.c (gen_lowpart): When requesting the low-part of a
+	MEM, try loading the MEM into a register and taking the low-part
+	of that, to help CSE see the use of the MEM in its true mode.
+
 2002-03-05  Tom Tromey  <tromey@redhat.com>
 
 	* config/stormy16/stormy16.h (DWARF_LINE_MIN_INSTR_LENGTH):

gcc/emit-rtl.c

@@ -1371,6 +1371,12 @@ gen_lowpart (mode, x)
     {
       /* The only additional case we can do is MEM.  */
       int offset = 0;
+
+      /* The following exposes the use of "x" to CSE.  */
+      if (GET_MODE_SIZE (GET_MODE (x)) <= UNITS_PER_WORD
+	  && ! no_new_pseudos)
+	return gen_lowpart (mode, force_reg (GET_MODE (x), x));
+
       if (WORDS_BIG_ENDIAN)
 	offset = (MAX (GET_MODE_SIZE (GET_MODE (x)), UNITS_PER_WORD)
 		  - MAX (GET_MODE_SIZE (mode), UNITS_PER_WORD));