[X86][SSE] EltsFromConsecutiveLoads - add basic dereferenceable support

This patch checks to see if the vector element loads are based off a dereferenceable pointer that covers the entire vector width, in which case we don't need to have element loads at both extremes of the vector width - just the start (base pointer) of it.

Another step towards partial vector loads......

Differential Revision: https://reviews.llvm.org/D64205

llvm-svn: 365614
diff --git a/llvm/test/CodeGen/X86/load-partial.ll b/llvm/test/CodeGen/X86/load-partial.ll
index 6d8d663..a0a94b9 100644
--- a/llvm/test/CodeGen/X86/load-partial.ll
+++ b/llvm/test/CodeGen/X86/load-partial.ll
@@ -10,30 +10,14 @@
 ;
 
 define <4 x float> @load_float4_float3(<4 x float>* nocapture readonly dereferenceable(16)) {
-; SSE2-LABEL: load_float4_float3:
-; SSE2:       # %bb.0:
-; SSE2-NEXT:    movss {{.*#+}} xmm1 = mem[0],zero,zero,zero
-; SSE2-NEXT:    movsd {{.*#+}} xmm0 = mem[0],zero
-; SSE2-NEXT:    movlhps {{.*#+}} xmm0 = xmm0[0],xmm1[0]
-; SSE2-NEXT:    retq
-;
-; SSSE3-LABEL: load_float4_float3:
-; SSSE3:       # %bb.0:
-; SSSE3-NEXT:    movss {{.*#+}} xmm1 = mem[0],zero,zero,zero
-; SSSE3-NEXT:    movsd {{.*#+}} xmm0 = mem[0],zero
-; SSSE3-NEXT:    movlhps {{.*#+}} xmm0 = xmm0[0],xmm1[0]
-; SSSE3-NEXT:    retq
-;
-; SSE41-LABEL: load_float4_float3:
-; SSE41:       # %bb.0:
-; SSE41-NEXT:    movsd {{.*#+}} xmm0 = mem[0],zero
-; SSE41-NEXT:    insertps {{.*#+}} xmm0 = xmm0[0,1],mem[0],xmm0[3]
-; SSE41-NEXT:    retq
+; SSE-LABEL: load_float4_float3:
+; SSE:       # %bb.0:
+; SSE-NEXT:    movups (%rdi), %xmm0
+; SSE-NEXT:    retq
 ;
 ; AVX-LABEL: load_float4_float3:
 ; AVX:       # %bb.0:
-; AVX-NEXT:    vmovsd {{.*#+}} xmm0 = mem[0],zero
-; AVX-NEXT:    vinsertps {{.*#+}} xmm0 = xmm0[0,1],mem[0],xmm0[3]
+; AVX-NEXT:    vmovups (%rdi), %xmm0
 ; AVX-NEXT:    retq
   %p0 = getelementptr inbounds <4 x float>, <4 x float>* %0, i64 0, i64 0
   %p1 = getelementptr inbounds <4 x float>, <4 x float>* %0, i64 0, i64 1
@@ -48,30 +32,14 @@
 }
 
 define <8 x float> @load_float8_float3(<4 x float>* nocapture readonly dereferenceable(16)) {
-; SSE2-LABEL: load_float8_float3:
-; SSE2:       # %bb.0:
-; SSE2-NEXT:    movss {{.*#+}} xmm1 = mem[0],zero,zero,zero
-; SSE2-NEXT:    movsd {{.*#+}} xmm0 = mem[0],zero
-; SSE2-NEXT:    movlhps {{.*#+}} xmm0 = xmm0[0],xmm1[0]
-; SSE2-NEXT:    retq
-;
-; SSSE3-LABEL: load_float8_float3:
-; SSSE3:       # %bb.0:
-; SSSE3-NEXT:    movss {{.*#+}} xmm1 = mem[0],zero,zero,zero
-; SSSE3-NEXT:    movsd {{.*#+}} xmm0 = mem[0],zero
-; SSSE3-NEXT:    movlhps {{.*#+}} xmm0 = xmm0[0],xmm1[0]
-; SSSE3-NEXT:    retq
-;
-; SSE41-LABEL: load_float8_float3:
-; SSE41:       # %bb.0:
-; SSE41-NEXT:    movsd {{.*#+}} xmm0 = mem[0],zero
-; SSE41-NEXT:    insertps {{.*#+}} xmm0 = xmm0[0,1],mem[0],xmm0[3]
-; SSE41-NEXT:    retq
+; SSE-LABEL: load_float8_float3:
+; SSE:       # %bb.0:
+; SSE-NEXT:    movups (%rdi), %xmm0
+; SSE-NEXT:    retq
 ;
 ; AVX-LABEL: load_float8_float3:
 ; AVX:       # %bb.0:
-; AVX-NEXT:    vmovsd {{.*#+}} xmm0 = mem[0],zero
-; AVX-NEXT:    vinsertps {{.*#+}} xmm0 = xmm0[0,1],mem[0],xmm0[3]
+; AVX-NEXT:    vmovups (%rdi), %xmm0
 ; AVX-NEXT:    retq
   %p0 = getelementptr inbounds <4 x float>, <4 x float>* %0, i64 0, i64 0
   %p1 = getelementptr inbounds <4 x float>, <4 x float>* %0, i64 0, i64 1
@@ -199,10 +167,7 @@
 ;
 ; AVX-LABEL: load_double4_0u2u:
 ; AVX:       # %bb.0:
-; AVX-NEXT:    vmovsd {{.*#+}} xmm0 = mem[0],zero
-; AVX-NEXT:    vmovsd {{.*#+}} xmm1 = mem[0],zero
-; AVX-NEXT:    vinsertf128 $1, %xmm1, %ymm0, %ymm0
-; AVX-NEXT:    vmovddup {{.*#+}} ymm0 = ymm0[0,0,2,2]
+; AVX-NEXT:    vmovddup {{.*#+}} ymm0 = mem[0,0,2,2]
 ; AVX-NEXT:    retq
   %2 = load double, double* %0, align 8
   %3 = insertelement <4 x double> undef, double %2, i32 0