[Qemu-devel] [PATCH 0/7] Double-word tcg/optimize improvements

[Richard Henderson <rth@twiddle.net>]

In another thread we talked about doing the brcond2 -> brcond optimization
generically for LT/GTE comparisons vs zero.  That's patch 4 of this series.
In addition, it seemed trivial to go ahead and apply the existing code we
have for fully optimizing constant comparisons.

Tested host i686, guest alpha.  Where even the final patch activates during
the boot rom.  (FYI, implver is sorta like cpuid, querying cpu revision.)

0xfffffc0000003748:  implver    t0
0xfffffc000000374c:  cmpeq      t0,0x1,t1
0xfffffc0000003750:  bne        t1,0x40000003784

OP:
 ---- 0xfffffc0000003748
 movi_i32 ir1_0,$0x2
 movi_i32 ir1_1,$0x0

 ---- 0xfffffc000000374c
 movi_i32 tmp0,$0x1
 movi_i32 tmp1,$0x0
 setcond2_i32 ir2_0,ir1_0,ir1_1,tmp0,tmp1,eq
 movi_i32 ir2_1,$0x0

 ---- 0xfffffc0000003750
 mov_i32 tmp0,ir2_0
 mov_i32 tmp1,ir2_1
 movi_i32 tmp2,$0x0
 movi_i32 tmp3,$0x0
 brcond2_i32 tmp0,tmp1,tmp2,tmp3,ne,$0x0
 ...

OP after optimization and liveness analysis:
 ---- 0xfffffc0000003748
 movi_i32 ir1_0,$0x2
 movi_i32 ir1_1,$0x0

 ---- 0xfffffc000000374c
 nopn $0x2,$0x2
 nopn $0x2,$0x2
 movi_i32 ir2_0,$0x0
 movi_i32 ir2_1,$0x0

 ---- 0xfffffc0000003750
 nopn $0x2,$0x2
 nopn $0x2,$0x2
 nopn $0x2,$0x2
 nopn $0x2,$0x2
 nop 
 ...



r~


Richard Henderson (7):
  tcg: Split out swap_commutative as a subroutine
  tcg: Optimize add2 + sub2
  tcg: Swap commutative double-word comparisons
  tcg: Optimize double-word comparisons against zero
  tcg: Split out subroutines from do_constant_folding_cond
  tcg: Tidy brcond optimization
  tcg: Do constant folding on double-word comparisons

 tcg/optimize.c | 366 +++++++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 267 insertions(+), 99 deletions(-)

-- 
1.7.11.4