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

[Eli Friedman]

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?

-Eli