[Bug target/27827] [4.0 Regression] gcc 4 produces worse x87 code on all platforms than gcc 3

[bonzini at gnu dot org]

------- Comment #66 from bonzini at gnu dot org  2006-08-11 14:10 -------
(on bugzilla because I had problems sending mail to you)

> Just got your most recent update.  From what I can tell, you have applied
> your patch to the 4.1 series, so that the next 4.1 release will have the fix?

Yes.

> So, my question is that I notice the comment says:
>    * config/i386/i386.md: Add peephole2 to avoid "fld %st" instructions.
>
> Which, if its what we've been doing should be something like:
>    * config/i386/i386.md: Add peephole2 to substitute "fld" for memory-source 
>      "fmul"

No, what my patch does is exactly replacing "fld reg + fmul mem" with "fld mem
+ fmul reg,reg".  Maybe the ChangeLog is not completely descriptive, but the PR
number is there and will make things clear enough.

> BTW, it's going to remain the case that you must do at least -O2 to get
> this peephole invoked?

You can add -fpeephole2.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27827