[X86] Always prefer to lower a VECTOR_SHUFFLE into a BLENDI instead of SHUFP (or VPERM2X128).

This patch teaches method 'LowerVECTOR_SHUFFLE' to give higher precedence to
the check for 'isBlendMask'; the idea is that, when possible, we should firstly
check if a shuffle performs a blend, and in case, try to lower it into a BLENDI
instead of selecting a SHUFP or (worse) a VPERM2X128.

In general:
 - AVX VBLENDPS/D always have better latency and throughput than VPERM2F128;
 - BLENDPS/D instructions tend to always have better 'reciprocal throughput'
   than the equivalent SHUFPS/D;
 - Both BLENDPS/D and SHUFPS/D are often decoded into the same number of
   m-ops; however, a m-op obtained from a BLENDPS/D can be scheduled to more
   than one execution port.

This patch:
 - Moves the check for 'isBlendMask' immediately before the check for
   'isSHUFPMask' within method 'LowerVECTOR_SHUFFLE';
 - Updates existing tests for sse/avx shuffle/blend instructions to verify
   that we select (v)blendps/d when possible (instead of (v)shufps/d or
   vperm2f128).

llvm-svn: 211720

1 files changed, 2 insertions, 2 deletions

diff --git a/llvm/test/CodeGen/X86/combine-or.ll b/llvm/test/CodeGen/X86/combine-or.ll
index 572aded5e9a..ff807b98717 100644
--- a/llvm/test/CodeGen/X86/combine-or.ll
+++ b/llvm/test/CodeGen/X86/combine-or.ll
@@ -74,7 +74,7 @@ define <4 x i32> @test6(<4 x i32> %a, <4 x i32> %b) {
 }
 ; CHECK-LABEL: test6
 ; CHECK-NOT: xorps
-; CHECK: shufps
+; CHECK: blendps $12
 ; CHECK-NEXT: ret
 
 
@@ -86,7 +86,7 @@ define <4 x i32> @test7(<4 x i32> %a, <4 x i32> %b) {
 }
 ; CHECK-LABEL: test7
 ; CHECK-NOT: xorps
-; CHECK: shufps
+; CHECK: blendps $12
 ; CHECK-NEXT: ret