Re: [Qemu-devel] [PATCH] tcg: Optimize some forms of deposit.

[Alexander Graf]

On 27.10.2011, at 23:15, Richard Henderson wrote:

> If the deposit replaces the entire word, optimize to a move.
> 
> If we're inserting to the top of the word, avoid the mask of arg2
> as we'll be shifting out all of the garbage and shifting in zeros.
> 
> If the host is 32-bit, reduce a 64-bit deposit to a 32-bit deposit
> when possible.

This patch breaks qemu-system-ppc64 on ppc32 hosts:

IN: 
0x00000000fff08618:  mfmsr   r0
0x00000000fff0861c:  ori     r0,r0,48
0x00000000fff08620:  mtmsr   r0

OP:
 ---- 0xfff08618
 mov_i32 r0_0,msr_0
 mov_i32 r0_1,msr_1

 ---- 0xfff0861c
 movi_i32 tmp0,$0x30
 or_i32 r0_0,r0_0,tmp0

 ---- 0xfff08620
 movi_i32 nip_0,$0xfff08624
 movi_i32 nip_1,$0x0
 mov_i32 tmp1,r0_0
 movi_i32 tmp0,$store_msr
 call tmp0,$0x0,$0,tmp2,tmp1
 movi_i32 nip_0,$0xfff08624
 movi_i32 nip_1,$0x0
 exit_tb $0x0

OP after liveness analysis:
 ---- 0xfff08618
 mov_i32 r0_0,msr_0
 mov_i32 r0_1,msr_1

 ---- 0xfff0861c
 movi_i32 tmp0,$0x30
 or_i32 r0_0,r0_0,tmp0

 ---- 0xfff08620
 movi_i32 nip_0,$0xfff08624
 movi_i32 nip_1,$0x0
 mov_i32 tmp1,r0_0
 movi_i32 tmp0,$store_msr
 call tmp0,$0x0,$0,tmp2,tmp1
 movi_i32 nip_0,$0xfff08624
 movi_i32 nip_1,$0x0
 exit_tb $0x0
 end 


address@hidden:/home/agraf/release/qemu> ./ppc64-softmmu/qemu-system-ppc64 
-kernel /boot/vmlinux -initrd /boot/initrd -nographic -d 
in_asm,cpu,int,op,op_opt,out_asm
/home/agraf/release/qemu/tcg/tcg.c:1929: tcg fatal error
Aborted



Alex