// Step 2: unpcklps X, Y ==> <3, 2, 1, 0>
unsigned EltStride = NumElems >> 1;
while (EltStride != 0) {
- for (unsigned i = 0; i < EltStride; ++i)
+ for (unsigned i = 0; i < EltStride; ++i) {
+ // If V[i+EltStride] is undef and this is the first round of mixing,
+ // then it is safe to just drop this shuffle: V[i] is already in the
+ // right place, the one element (since it's the first round) being
+ // inserted as undef can be dropped. This isn't safe for successive
+ // rounds because they will permute elements within both vectors.
+ if (V[i+EltStride].getOpcode() == ISD::UNDEF &&
+ EltStride == NumElems/2)
+ continue;
+
V[i] = getUnpackl(DAG, dl, VT, V[i], V[i + EltStride]);
+ }
EltStride >>= 1;
}
return V[0];
; %c = sext <4 x i16> %a to <4 x i32> ; <<4 x i32>> [#uses=1]
; ret <4 x i32> %c
;}
+
+; This should not emit shuffles to populate the top 2 elements of the 4-element
+; vector that this ends up returning.
+; rdar://8368414
+define <2 x float> @test4(<2 x float> %A, <2 x float> %B) nounwind {
+entry:
+ %tmp7 = extractelement <2 x float> %A, i32 0
+ %tmp5 = extractelement <2 x float> %A, i32 1
+ %tmp3 = extractelement <2 x float> %B, i32 0
+ %tmp1 = extractelement <2 x float> %B, i32 1
+ %add.r = fadd float %tmp7, %tmp3
+ %add.i = fsub float %tmp5, %tmp1
+ %tmp11 = insertelement <2 x float> undef, float %add.r, i32 0
+ %tmp9 = insertelement <2 x float> %tmp11, float %add.i, i32 1
+ ret <2 x float> %tmp9
+; CHECK: test4:
+; CHECK-NOT: shufps $16
+; CHECK: shufps $1,
+; CHECK-NOT: shufps $16
+; CHECK: shufps $1,
+; CHECK-NOT: shufps $16
+; CHECK: unpcklps
+; CHECK-NOT: shufps $16
+; CHECK: ret
+}