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

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 8af66894ea29c33f097abb95776814196e227066..3850c9814b196830d19546c4a24c5ff5e0f3e2b5 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+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):

diff --git a/gcc/emit-rtl.c b/gcc/emit-rtl.c
index dbc0a372a3b0aeab9fb3e735390a4b578b11f202..c96bc4e200e79bfab6a51f1f40e0f08cf17b7b30 100644 (file)
--- a/gcc/emit-rtl.c
+++ b/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));