[X86][SSE]] Lower BUILD_VECTOR with repeated elts as BUILD_VECTOR + VECTOR_SHUFFLE

It can be costly to transfer from the gprs to the xmm registers and can prevent loads merging.

This patch splits vXi16/vXi32/vXi64 BUILD_VECTORS that use the same operand in multiple elements into a BUILD_VECTOR with only a single insertion of each of those elements and then performs an unary shuffle to duplicate the values.

There are a couple of minor regressions this patch unearths due to some missing MOVDDUP/BROADCAST folds that I will address in a future patch.

Note: Now that vector shuffle lowering and combining is pretty good we should be reusing that instead of duplicating so much in LowerBUILD_VECTOR - this is the first of several patches to address this.

Differential Revision: https://reviews.llvm.org/D31373

llvm-svn: 299387

1 files changed, 3 insertions, 6 deletions

diff --git a/llvm/test/CodeGen/X86/vshift-1.ll b/llvm/test/CodeGen/X86/vshift-1.ll
index 7ad5706592e..4bc65908ed6 100644
--- a/llvm/test/CodeGen/X86/vshift-1.ll
+++ b/llvm/test/CodeGen/X86/vshift-1.ll
@@ -28,12 +28,9 @@ define void @shift1b(<2 x i64> %val, <2 x i64>* %dst, i64 %amt) nounwind {
 ; X32-LABEL: shift1b:
 ; X32:       # BB#0: # %entry
 ; X32-NEXT:    movl {{[0-9]+}}(%esp), %eax
-; X32-NEXT:    movd {{.*#+}} xmm1 = mem[0],zero,zero,zero
-; X32-NEXT:    pshufd {{.*#+}} xmm1 = xmm1[0,0,1,1]
-; X32-NEXT:    movd {{.*#+}} xmm2 = mem[0],zero,zero,zero
-; X32-NEXT:    pshufd {{.*#+}} xmm2 = xmm2[0,0,1,1]
-; X32-NEXT:    punpckldq {{.*#+}} xmm2 = xmm2[0],xmm1[0],xmm2[1],xmm1[1]
-; X32-NEXT:    psllq %xmm2, %xmm0
+; X32-NEXT:    movq {{.*#+}} xmm1 = mem[0],zero
+; X32-NEXT:    pshufd {{.*#+}} xmm1 = xmm1[0,1,0,1]
+; X32-NEXT:    psllq %xmm1, %xmm0
 ; X32-NEXT:    movdqa %xmm0, (%eax)
 ; X32-NEXT:    retl
 ;