Re: [Qemu-devel] [PATCH v2 00/10] Double-word tcg/optimize improvements

[Aurelien Jarno]

On Tue, Oct 02, 2012 at 11:32:20AM -0700, Richard Henderson wrote:
> Changes v1->v2:
> 
> * Patch 1 changes the exact swap condition.  This helps add2 for e.g.
> 
>     add2 tmp4,tmp5,tmp4,tmp5,c1,c2
> 
>   where tmp5, c1, and c2 are all input constants.  Since tmp4 is variable,
>   we cannot constant fold this.  But the existing swap condition would give
> 
>     add2 tmp4.tmp5,tmp4,c2,c1,tmp5
> 
>   While not incorrect, we do want to prefer "adc $c2,tmp5" on i686.
> 
> * Patch 2 drops the partial constant folding for add2/sub2.  It only
>   does the operand ordering for add2.
> 
> * Patch 4 is new.  When writing the code for brcond2 et al, it did seem
>   silly to do all the gen_args[N] = args[N] copying by hand.  I think the
>   patch makes the code more readable.
> 
> * Patch 5 has the operand typo fixed that Aurelien noticed.
> 
> * Patch 8 is new, adding the extra nop into the opcode stream that
>   was suggested on the list.  With this we fully constant fold add2/sub2.
> 
> * Patch 9 is new.  While looking at dumps from x86_64 bios boot, I noticed
>   that sequences of push/pop insns leave the high-part of %rsp dead.   And
>   in general any 32-bit addition in which the high-part isn't "consumed"
>   by cc_dst.
> 
> * Patch 10 is new, treating mulu2 similarly to add2.  It triggers frequently
>   during the boot of seabios, and should not be expensive.
> 
> 
> r~
> 
> 
> Richard Henderson (10):
>   tcg: Split out swap_commutative as a subroutine
>   tcg: Canonicalize add2 operand ordering
>   tcg: Swap commutative double-word comparisons
>   tcg: Use common code when failing to optimize
>   tcg: Optimize double-word comparisons against zero
>   tcg: Split out subroutines from do_constant_folding_cond
>   tcg: Do constant folding on double-word comparisons
>   tcg: Constant fold add2 and sub2
>   tcg: Optimize half-dead add2/sub2
>   tcg: Optimize mulu2
> 
>  tcg/optimize.c | 465 
> ++++++++++++++++++++++++++++++++++++++-------------------
>  tcg/tcg-op.h   |  11 ++
>  tcg/tcg.c      |  53 ++++++-
>  3 files changed, 377 insertions(+), 152 deletions(-)
> 

All applied, after fixing the conflicts in patch 6.


-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
address@hidden                 http://www.aurel32.net