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Re: [Qemu-devel] [PATCH] tcg: Fix tcg_reg_alloc_mov vs no-op truncation
From: |
Tom Musta |
Subject: |
Re: [Qemu-devel] [PATCH] tcg: Fix tcg_reg_alloc_mov vs no-op truncation |
Date: |
Tue, 13 May 2014 17:13:24 -0500 |
User-agent: |
Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 |
On 5/13/2014 4:59 PM, Richard Henderson wrote:
> Commit af3cbfbe8018ccc16fb3a0048e928f66f0d05e87 hoisted some "common"
> loads of the temporary type, forgetting that the types could differ
> during truncating moves. This affects the correctness of the memory
> offset on big-endian hosts.
>
> Signed-off-by: Richard Henderson <address@hidden>
Tested-by: Tom Musta <address@hidden>
Works functionally and also the low level traces look better:
---
IN:
0x00000fff79d62ae4: rlwimi r4,r4,8,16,23
OP:
ld_i32 tmp0,env,$0xfffffffffffffffc
movi_i32 tmp1,$0x0
brcond_i32 tmp0,tmp1,ne,$0x0
---- 0xfff79d62ae4
mov_i32 tmp0,r4
movi_i32 tmp1,$0x8
rotl_i32 tmp0,tmp0,tmp1
movi_i64 tmp3,$0xffffffff
and_i64 tmp2,tmp0,tmp3
movi_i64 tmp4,$0xff00
and_i64 tmp2,tmp2,tmp4
movi_i64 tmp4,$0xffffffffffff00ff
and_i64 tmp3,r4,tmp4
or_i64 r4,tmp2,tmp3
goto_tb $0x0
movi_i64 nip,$0xfff79d62ae8
exit_tb $0xfff79e7dc30
set_label $0x0
exit_tb $0xfff79e7dc33
OUT: [size=136]
0x60363920: lwz r14,-4(r27)
0x60363924: cmpwi cr7,r14,0
0x60363928: bne- cr7,0x60363994
0x6036392c: ld r14,32(r27) # TEM -- looks better
0x60363930: mr r15,r14
0x60363934: rotlwi r15,r15,8
0x60363938: andi. r15,r15,65280
0x6036393c: lis r0,-1
0x60363940: ori r0,r0,255
0x60363944: and r14,r14,r0
0x60363948: or r14,r15,r14
0x6036394c: std r14,32(r27)
0x60363950: .long 0x0
0x60363954: .long 0x0
0x60363958: .long 0x0
...
NIP 00000fff79d62ae8 LR 00000fff79d55af0 CTR 0000000000000007 XER
0000000000000000
MSR 8000000002006000 HID0 0000000000000000 HF 0000000002006000 idx 0
TB 00000000 00000000
GPR00 00000000100002d9 0000004000a0e040 00000fff79d88ae8 00000000100002d9
GPR04 0000000000002424 0000000000000000 0000000000000000 0000000000000000
# TEM so does GPR04
GPR08 0000000000000000 0000000010010978 000000007fffffff 0000000000000001