* Re: compile/920501-18.c and -fssa
@ 2000-09-18 9:18 Brad Lucier
0 siblings, 0 replies; 3+ messages in thread
From: Brad Lucier @ 2000-09-18 9:18 UTC (permalink / raw)
To: mark; +Cc: lucier, gcc, kenner
Mark Mitchell wrote:
> >>>>> "Richard" == Richard Kenner <kenner@vlsi1.ultra.nyu.edu> writes:
>
> Richard> I think there's something wrong with the transformation
> Richard> of the loop. Could somebody who understands the SSA
> Richard> stuff please verify?
>
> There are known issues with SSA, basically because the design of
> RTL-generation involves generating overly low-level constructs early
> in the game. Therefore, I wouldn't suggest we spend effort on this at
> the moment.
On the Alpha 21264, -fssa reorders floating-point code in a manner that
happens to work around a difficulty in gcc's register allocator for IEEE
floating-point arithmetic; see a series of e-mails in
http://gcc.gnu.org/ml/gcc/2000-03/
with the (rather unfortunate) title
-fssa kicks butt on alphaev6 ieee floating point code
On alphaev6-unknown-linux-gnu, then gcc.c-torture/compile/920501-18.c is
the *only* test that fails with -fssa and does not fail with other
compile options. So please, let's not abandon it yet.
> In fact, I think it's probably a waste of time to run
> with -fssa in the testsuite, for now.
I disagree.
Brad Lucier
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: compile/920501-18.c and -fssa
2000-09-17 4:54 Richard Kenner
@ 2000-09-17 10:30 ` Mark Mitchell
0 siblings, 0 replies; 3+ messages in thread
From: Mark Mitchell @ 2000-09-17 10:30 UTC (permalink / raw)
To: kenner; +Cc: gcc
>>>>> "Richard" == Richard Kenner <kenner@vlsi1.ultra.nyu.edu> writes:
Richard> I think there's something wrong with the transformation
Richard> of the loop. Could somebody who understands the SSA
Richard> stuff please verify?
There are known issues with SSA, basically because the design of
RTL-generation involves generating overly low-level constructs early
in the game. Therefore, I wouldn't suggest we spend effort on this at
the moment. In fact, I think it's probably a waste of time to run
with -fssa in the testsuite, for now.
--
Mark Mitchell mark@codesourcery.com
CodeSourcery, LLC http://www.codesourcery.com
^ permalink raw reply [flat|nested] 3+ messages in thread
* compile/920501-18.c and -fssa
@ 2000-09-17 4:54 Richard Kenner
2000-09-17 10:30 ` Mark Mitchell
0 siblings, 1 reply; 3+ messages in thread
From: Richard Kenner @ 2000-09-17 4:54 UTC (permalink / raw)
To: gcc
I think there's something wrong with the transformation of the loop.
Could somebody who understands the SSA stuff please verify?
Thanks.
^ permalink raw reply [flat|nested] 3+ messages in thread
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