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- To: law at cygnus dot com
- From: john at feith dot com (John Wehle)
- Date: Mon, 1 Jun 1998 12:05:28 -0400
- cc: egcs-patches at cygnus dot com
> Well, my experiments how this is generally a lose, though a rather
> small one. Have you done any experiments which show that register
> allocation is improved with this patch?
Crafty (a chess program) shows a 2 percent improvement on its internal
benchmark when using this patch and compiled in both cases with
-march=pentiumpro -O3. The assembler resulting from compiling with
-O (without specifiying -march) cse.c, gcse.c, optabs.c, and reload1.c
shows changes similar to:
***************
*** 6447,6456 ****
cmpw $50,(%ecx)
jne L1067
movzbl 2(%edx),%eax
! cmpl %eax,12(%ebp)
jne L1067
! movzbl 2(%ecx),%edx
! cmpl %edx,12(%ebp)
jne L1067
leal -72(%ebp),%eax
pushl %eax
--- 6447,6457 ----
cmpw $50,(%ecx)
jne L1067
movzbl 2(%edx),%eax
! movl 12(%ebp),%edx
! cmpl %eax,%edx
jne L1067
! movzbl 2(%ecx),%eax
! cmpl %eax,%edx
jne L1067
leal -72(%ebp),%eax
pushl %eax
Which appears to better register usage. Can you supply a example of
where it loses?
-- John
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