This is the mail archive of the mailing list for the GCC project.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: Shouldn't convert_scalars_to_vector call free_dominance_info?

On Thu, Mar 10, 2016 at 12:18 PM, Richard Biener
<> wrote:
> On March 10, 2016 6:02:58 PM GMT+01:00, "H.J. Lu" <> wrote:
>>On Thu, Mar 10, 2016 at 6:57 AM, H.J. Lu <> wrote:
>>> On Thu, Mar 10, 2016 at 5:49 AM, Jakub Jelinek <>
>>>> On Thu, Mar 10, 2016 at 05:43:27AM -0800, H.J. Lu wrote:
>>>>> > free_dominance_info (CDI_DOMINATORS);
>>>>> Since convert_scalars_to_vector may add instructions, dominance
>>>>> info is no longer up to date.
>>>> Adding instructions doesn't change anything on the dominance info,
>>>> cfg manipulations that don't keep the dominators updated.
>>>> You can try to verify the dominance info at the end of the stv pass,
>>> I added
>>> verify_dominators (CDI_DOMINATORS);
>>> '
>>> It did trigger assert in my 64-bit STV pass in 64-bit libgcc build:
>>> /export/gnu/import/git/sources/gcc/libgcc/config/libbid/bid128_fma.c:
>>> In function \u2018add_and_round.constprop\u2019:
>>> error: dominator of 158 should be 107, not 101
>>> I will investigate.
>>Here is the problem:
>>1. I extended the STV pass to 64-bit to convert TI load/store to
>>V1TI load/store to use SSE load/store for 128-bit load/store.
>>2. The 64-bit STV pass generates settings of CONST0_RTX and
>>CONSTM1_RTX to store 128-bit 0 and -1.
>>3. I placed the 64-bit STV pass before the CSE pass so that
>>CONST0_RTX and CONSTM1_RTX generated by the STV pass
>>can be CSEed.
>>4. After settings of CONST0_RTX and CONSTM1_RTX are CSEed,
>>dominance info will be wrong.

It isn't just CONST0_RTX and CONSTM1_RTX.   Any instructions
changed or generated by the STV pass may be CSEed.

> Can't see how cse can ever invalidate dominators.

CSE may remove statements touched by the 64-bit STV pass.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]