On Tue, Jan 8, 2013 at 6:42 PM, Richard Biener
<richard.guent...@gmail.com> wrote:
> On Tue, Jan 8, 2013 at 8:51 AM, Bin.Cheng <amker.ch...@gmail.com> wrote:
>> Hi,
>> For attached preprocessed file, dump file
>> lib_a-s_frexp.E.021t.copyrename1 contains gimple sequences like:
>>
>> <bb 4>:
>> x_41 = x_8(D);
>> goto <bb 8>;
>>
>> <bb 5>:
>> if (ix_15 <= 1048575)
>> goto <bb 6>;
>> else
>> goto <bb 7>;
>>
>> <bb 6>:
>> x_19 = x_8(D) * 1.8014398509481984e+16;
>> gh_u.value = x_19;
>> _21 = gh_u.parts.msw;
>> hx_22 = (__int32_t) _21;
>> gh_u ={v} {CLOBBER};
>> ix_24 = hx_22 & 2147483647;
>> *eptr_16(D) = -54;
>>
>> <bb 7>:
>> # x_1 = PHI <x_8(D)(5), x_19(6)>
>> # hx_2 = PHI <hx_11(5), hx_22(6)>
>> # ix_3 = PHI <ix_15(5), ix_24(6)>
>> _26 = *eptr_16(D);
>> _27 = ix_3 >> 20;
>> _28 = _27 + -1022;
>> _29 = _26 + _28;
>> *eptr_16(D) = _29;
>> hx.0_31 = (unsigned int) hx_2;
>> _32 = hx.0_31 & 2148532223;
>> _33 = _32 | 1071644672;
>> hx_34 = (__int32_t) _33;
>> sh_u.value = x_1;
>> hx.1_36 = (unsigned int) hx_34;
>> sh_u.parts.msw = hx.1_36;
>> x_38 = sh_u.value;
>> sh_u ={v} {CLOBBER};
>> x_40 = x_38;
>>
>> <bb 8>:
>> # _4 = PHI <x_41(4), x_40(7)>
>> return _4;
>>
>> I am not sure if phi node (_4, x_41, x_40) in basic block 8 should be
>> rename/partitioned into one partition.
>> Trunk does not do this rename/partition, which causing big regression
>> in code size on Thumb1.
>>
>> BTW, the command line is:
>> arm-none-eabi-gcc -mthumb -mcpu=cortex-m0 -Os/-O2 ...
>>
>> I noticed the behavior is intended by PR54200, but not sure how the
>> issue should be handled. Any suggestions?
>
> Missed coalescing should be handled by adjusting the out-of-SSA coalescing
> code, not by copyrename (which really should go - it should not be needed
> with VTA and var-tracking around).
>
> Richard.
>
Thanks for answering, I will learn that part of code.
--
Best Regards.
