This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
RFA: regrename: Don't record high part copies
- From: Joern Rennecke <joern dot rennecke at superh dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Tue, 16 Jul 2002 19:38:25 +0100
- Subject: RFA: regrename: Don't record high part copies
- Organization: SuperH UK Ltd.
--
--------------------------
SuperH
2430 Aztec West / Almondsbury / BRISTOL / BS32 4AQ
T:+44 1454 462330
Tue Jul 16 19:32:58 2002 J"orn Rennecke <joern.rennecke@superh.com>
* regrename.c (copy_value): Don't record high part copies.
Index: regrename.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/regrename.c,v
retrieving revision 1.54
diff -p -r1.54 regrename.c
*** regrename.c 16 Jul 2002 10:59:15 -0000 1.54
--- regrename.c 16 Jul 2002 18:32:54 -0000
*************** copy_value (dest, src, vd)
*** 1268,1273 ****
--- 1268,1293 ----
if (vd->e[sr].mode == VOIDmode)
set_value_regno (sr, vd->e[dr].mode, vd);
+ /* If we are narrowing the the input to a smaller number of hard regs,
+ and it is in big endian, we are really extracting a high part.
+ Since we generally associate a low part of a value with the value itself,
+ we must not do the same for the high part.
+ Note we can still get low parts for the same mode combination through
+ a two-step copy involving differently sized hard regs.
+ Assume hard regs fr* are 32 bits bits each, while r* are 64 bits each:
+ (set (reg:DI r0) (reg:DI fr0))
+ (set (reg:SI fr2) (reg:SI r0))
+ loads the low part of (reg:DI fr0) - i.e. fr1 - into fr2, while:
+ (set (reg:SI fr2) (reg:SI fr0))
+ loads the high part of (reg:DI fr0) into fr2.
+
+ We can't properly represent the latter case in our tables, so don't
+ record anything then. */
+ else if (sn < HARD_REGNO_NREGS (sr, vd->e[sr].mode)
+ && (GET_MODE_SIZE (vd->e[sr].mode) > UNITS_PER_WORD
+ ? WORDS_BIG_ENDIAN : BYTES_BIG_ENDIAN))
+ return;
+
/* If SRC had been assigned a mode narrower than the copy, we can't
link DEST into the chain, because not all of the pieces of the
copy came from oldest_regno. */