* Advice needed how to avoid generation of extra sign_extends in .md file
@ 2002-10-03 18:07 Igor Shevlyakov
2002-10-03 19:14 ` Richard Henderson
2002-10-04 9:51 ` Jim Wilson
0 siblings, 2 replies; 3+ messages in thread
From: Igor Shevlyakov @ 2002-10-03 18:07 UTC (permalink / raw)
To: gcc, gcc-help
Hi everybody,
I wonder if somebody know how to make back-end generate better code
under following conditions:
- 32 bit opearations always sign extend their result into whole 64-bit
result registers.
- conditional branches work only on 64-bit registers
- loads are always sign-extending.
now if we have
int64 a, b;
int32 c, d, f;
c = d + f;
a = b + c;
How to avoid sign_extend before second plus since result of 'addsi3' was
already extended?
Even worse:
int16 *pi, j;
int64 a,b;
j = *pi + 3;
a = b + j;
Doesn't really requires any extensions since *pi already sign extended
target register and we could use same instruction to add 16-bits as for
add 32-bits and result will be 64-bit sign extended in that case.
But I couldn't come up with idea how to teach .md file all that.
Thanks a lot
Igor
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Advice needed how to avoid generation of extra sign_extends in .md file
2002-10-03 18:07 Advice needed how to avoid generation of extra sign_extends in .md file Igor Shevlyakov
@ 2002-10-03 19:14 ` Richard Henderson
2002-10-04 9:51 ` Jim Wilson
1 sibling, 0 replies; 3+ messages in thread
From: Richard Henderson @ 2002-10-03 19:14 UTC (permalink / raw)
To: Igor Shevlyakov; +Cc: gcc, gcc-help
On Thu, Oct 03, 2002 at 06:09:21PM -0700, Igor Shevlyakov wrote:
> - 32 bit opearations always sign extend their result into whole 64-bit
> result registers.
> - conditional branches work only on 64-bit registers
> - loads are always sign-extending.
See the alpha port, which has these same characteristics.
r~
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Advice needed how to avoid generation of extra sign_extends in .md file
2002-10-03 18:07 Advice needed how to avoid generation of extra sign_extends in .md file Igor Shevlyakov
2002-10-03 19:14 ` Richard Henderson
@ 2002-10-04 9:51 ` Jim Wilson
1 sibling, 0 replies; 3+ messages in thread
From: Jim Wilson @ 2002-10-04 9:51 UTC (permalink / raw)
To: Igor Shevlyakov; +Cc: gcc, gcc-help
See also the MIPS port which also has the same problem, and which uses a
different solution than the alpha port. I don't know offhand which solution
is better.
Jim
^ permalink raw reply [flat|nested] 3+ messages in thread
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2002-10-03 18:07 Advice needed how to avoid generation of extra sign_extends in .md file Igor Shevlyakov
2002-10-03 19:14 ` Richard Henderson
2002-10-04 9:51 ` Jim Wilson
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