[llvm-commits] [RFC/PATCH] introduce 'UseSSEx' predicates

[Eli Friedman]

On Fri, Aug 24, 2012 at 6:55 PM, Michael Liao <michael.liao at intel.com> wrote:
> On Fri, 2012-08-24 at 18:14 -0700, Eli Friedman wrote:
>> On Wed, Aug 22, 2012 at 10:27 AM, Michael Liao <michael.liao at intel.com> wrote:
>> > Hi
>> >
>> > The attached patch adds several new predicates, namely UseSSE1, UseSSE2,
>> > UseSSE3, UseSSSE3, UseSSE41, and UseSSE42.
>> >
>> > As the penalty of inter-mixing SSE and AVX instructions, we need prevent
>> > SSE legacy insn from being generated except explicitly specified through
>> > some intrinsics. For patterns both supported by both SSE and AVX, so
>> > far, we force AVX insn will be tried first relying on AddedComplexity or
>> > td location. It's error-prone and introduces bugs accidentally.
>> >
>> > 'UseSSEx' is disabled when AVX is turned on. For insns both supported by
>> > AVX and SSE insns, we need this predicate to force VEX encoding only.
>> >
>> > For insns not inherited by AVX, we still use the previous predicates,
>> > i.e. 'HasSSEx'. So far, these insns fall into the following categories:
>> >   * SSE insns with MMX operands
>> >   * SSE insns with GPR/mem operands only (xFENCE, PREFETCH, CLFLUSH,
>> >     CRC, and etc.)
>> >   * SSE4A insns.
>> >   * MMX insns.
>> >   * x87 insns added by SSE.
>> >
>> > With this patch, several inter-mixing cases are found and fixed from
>> > regression tests.
>>
>> --- a/test/ExecutionEngine/MCJIT/test-common-symbols.ll
>> +++ b/test/ExecutionEngine/MCJIT/test-common-symbols.ll
>> @@ -1,4 +1,4 @@
>> -; RUN: %lli -use-mcjit -O0 -disable-lazy-compilation=false %s
>> +; RUN: %lli -use-mcjit -disable-lazy-compilation=false %s
>>
>>  ; The intention of this test is to verify that symbols mapped to COMMON in ELF
>>  ; work as expected.
>>
>> What is the point of this change?
>
> So far, MCJIT cannot support the creation of '.rodata' section. This's
> work around. I will file a bug for MCJIT.

Oh, I see...

How hard would it be to fix fast-isel so it can select vcvtsi2sdq?

-Eli