[SelectionDAG] Add SIGN_EXTEND_VECTOR_INREG support to computeKnownBits.

[RKSimon]

LGTM

llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

KnownBits SelectionDAG::computeKnownBits(SDValue Op, const APInt &DemandedElts,
   }
   case ISD::ZERO_EXTEND: {
     EVT InVT = Op.getOperand(0).getValueType();
     Known = computeKnownBits(Op.getOperand(0), DemandedElts, Depth + 1);
     Known = Known.zext(BitWidth);
     Known.Zero.setBitsFrom(InVT.getScalarSizeInBits());
     break;
   }
-  // TODO ISD::SIGN_EXTEND_VECTOR_INREG
+  case ISD::SIGN_EXTEND_VECTOR_INREG: {
+    EVT InVT = Op.getOperand(0).getValueType();
+    APInt InDemandedElts = DemandedElts.zextOrSelf(InVT.getVectorNumElements());
+    Known = computeKnownBits(Op.getOperand(0), InDemandedElts, Depth + 1);
+    // If the sign bit is known to be zero or one, then sext will extend
+    // it to the top bits, else it will just zext.
+    Known = Known.sext(BitWidth);
+    break;
+  }
   case ISD::SIGN_EXTEND: {
     Known = computeKnownBits(Op.getOperand(0), DemandedElts, Depth + 1);
     // If the sign bit is known to be zero or one, then sext will extend
     // it to the top bits, else it will just zext.
     Known = Known.sext(BitWidth);
     break;
   }
   case ISD::ANY_EXTEND: {

llvm/trunk/test/CodeGen/X86/combine-shl.ll

 ; SSE2-NEXT:    pslld $30, %xmm0
 ; SSE2-NEXT:    xorpd %xmm2, %xmm2
 ; SSE2-NEXT:    movsd {{.*#+}} xmm0 = xmm2[0],xmm0[1]
 ; SSE2-NEXT:    retq
 ;
 ; SSE41-LABEL: combine_vec_shl_ext_shl1:
 ; SSE41:       # %bb.0:
 ; SSE41-NEXT:    pmullw {{.*}}(%rip), %xmm0
-; SSE41-NEXT:    pshufd {{.*#+}} xmm1 = xmm0[2,3,0,1]
-; SSE41-NEXT:    pmovsxwd %xmm1, %xmm1
 ; SSE41-NEXT:    pmovsxwd %xmm0, %xmm0
-; SSE41-NEXT:    movdqa %xmm0, %xmm2
-; SSE41-NEXT:    pslld $30, %xmm2
-; SSE41-NEXT:    pslld $31, %xmm0
-; SSE41-NEXT:    pblendw {{.*#+}} xmm0 = xmm0[0,1,2,3],xmm2[4,5,6,7]
-; SSE41-NEXT:    movdqa %xmm1, %xmm2
-; SSE41-NEXT:    pslld $28, %xmm2
-; SSE41-NEXT:    pslld $29, %xmm1
-; SSE41-NEXT:    pblendw {{.*#+}} xmm1 = xmm1[0,1,2,3],xmm2[4,5,6,7]
+; SSE41-NEXT:    pslld $30, %xmm0
+; SSE41-NEXT:    pxor %xmm1, %xmm1
+; SSE41-NEXT:    pblendw {{.*#+}} xmm0 = xmm1[0,1,2,3],xmm0[4,5,6,7]
+; SSE41-NEXT:    pxor %xmm1, %xmm1
 ; SSE41-NEXT:    retq
 ;
 ; AVX-LABEL: combine_vec_shl_ext_shl1:
 ; AVX:       # %bb.0:
 ; AVX-NEXT:    vpmullw {{.*}}(%rip), %xmm0, %xmm0
 ; AVX-NEXT:    vpmovsxwd %xmm0, %ymm0
 ; AVX-NEXT:    vpsllvd {{.*}}(%rip), %ymm0, %ymm0
 ; AVX-NEXT:    retq