Enhance DAGCombine for transforming 128->256 casts into a vmovaps, rather

then a vxorps + vinsertf128 pair if the original vector came from a load.
rdar://10594409

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147481 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/X86/X86ISelLowering.cpp

@@ -12731,6 +12731,20 @@ static SDValue PerformShuffleCombine256(SDNode *N, SelectionDAG &DAG,
           !isUndefOrEqual(SVOp->getMaskElt(i+NumElems/2), NumElems))
         return SDValue();
 
+    // If V1 is coming from a vector load then just fold to a VZEXT_LOAD.
+    if (LoadSDNode *Ld = dyn_cast<LoadSDNode>(V1.getOperand(0))) {
+      SDVTList Tys = DAG.getVTList(MVT::v4i64, MVT::Other);
+      SDValue Ops[] = { Ld->getChain(), Ld->getBasePtr() };
+      SDValue ResNode =
+        DAG.getMemIntrinsicNode(X86ISD::VZEXT_LOAD, dl, Tys, Ops, 2,
+                                Ld->getMemoryVT(),
+                                Ld->getPointerInfo(),
+                                Ld->getAlignment(),
+                                false/*isVolatile*/, true/*ReadMem*/,
+                                false/*WriteMem*/);
+      return DAG.getNode(ISD::BITCAST, dl, VT, ResNode);
+    } 
+
     // Emit a zeroed vector and insert the desired subvector on its
     // first half.
     SDValue Zeros = getZeroVector(VT, true /* HasXMMInt */, DAG, dl);

lib/Target/X86/X86InstrSSE.td

@@ -4719,6 +4719,11 @@ let Predicates = [HasAVX], AddedComplexity = 20 in {
             (VMOVZQI2PQIrm addr:$src)>;
 }
 
+let Predicates = [HasAVX] in {
+def : Pat<(v4i64 (X86vzload addr:$src)),
+          (SUBREG_TO_REG (i32 0), (VMOVAPSrm addr:$src), sub_xmm)>;
+}
+
 //===---------------------------------------------------------------------===//
 // Moving from XMM to XMM and clear upper 64 bits. Note, there is a bug in
 // IA32 document. movq xmm1, xmm2 does clear the high bits.

test/CodeGen/X86/avx-shuffle.ll

@@ -31,4 +31,27 @@ define <8 x float> @test4(float %a) nounwind {
   ret <8 x float> %b
 ; CHECK: test4:
 ; CHECK: vinsertf128
+}
+
+; rdar://10594409
+define <8 x float> @test5(float* nocapture %f) nounwind uwtable readonly ssp {
+entry:
+  %0 = bitcast float* %f to <4 x float>*
+  %1 = load <4 x float>* %0, align 16
+; CHECK: vmovaps
+; CHECK-NOT: vxorps
+; CHECK-NOT: vinsertf128
+  %shuffle.i = shufflevector <4 x float> %1, <4 x float> <float 0.000000e+00, float undef, float undef, float undef>, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 4, i32 4, i32 4>
+  ret <8 x float> %shuffle.i
+}
+
+define <4 x double> @test6(double* nocapture %d) nounwind uwtable readonly ssp {
+entry:
+  %0 = bitcast double* %d to <2 x double>*
+  %1 = load <2 x double>* %0, align 16
+; CHECK: vmovaps
+; CHECK-NOT: vxorps
+; CHECK-NOT: vinsertf128
+  %shuffle.i = shufflevector <2 x double> %1, <2 x double> <double 0.000000e+00, double undef>, <4 x i32> <i32 0, i32 1, i32 2, i32 2>
+  ret <4 x double> %shuffle.i
 }