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Changing the number of regs
- From: Rahul Gupta <rahulgupta at in dot ibm dot com>
- To: gcc at gcc dot gnu dot org
- Date: Wed, 7 Jul 2004 01:31:35 +0530
- Subject: Changing the number of regs
Hi ,
I am trying out some register allocators for gcc. For comparison purposes,
I need to change the number of registers to some low number like 8 or 16.
The arch is i386 and I am looking the gcc/config/386/i386.h file.
I tried changing FIRST_PSEUDO_REGISTER 's value but there were many
dependencies which caused the compilation to abort. Next I tried changing
the FIXED_REGISTERS bits to 1 for some of the float/mmx/normal regs,
thereby making the number of unset bits to be 8. I didnt change
FIRST_PSEUDO_REGISTER. This compiled okay but I checked it on some
benchmark with more than 8 live webs at various program points. It gave me
a zero spill cost allocation where there were only 8 available regs. Please
guide me as to how to go about making the necessary changes to reduce the
number of registers.
Thanks and regards,
Rahul