Fix for PR20648 - http://llvm.org/bugs/show_bug.cgi?id=20648
This patch checks the operands of a vselect to see if all values are constants.
If yes, bail out of any further attempts to create a blend or shuffle because
SelectionDAGLegalize knows how to turn this kind of vselect into a single load.
This already happens for machines without SSE4.1, so the added checks just send
more targets down that path.
Differential Revision: http://reviews.llvm.org/D4934
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216121
91177308-0d34-0410-b5e6-
96231b3b80d8
}
SDValue X86TargetLowering::LowerVSELECT(SDValue Op, SelectionDAG &DAG) const {
}
SDValue X86TargetLowering::LowerVSELECT(SDValue Op, SelectionDAG &DAG) const {
+ // A vselect where all conditions and data are constants can be optimized into
+ // a single vector load by SelectionDAGLegalize::ExpandBUILD_VECTOR().
+ if (ISD::isBuildVectorOfConstantSDNodes(Op.getOperand(0).getNode()) &&
+ ISD::isBuildVectorOfConstantSDNodes(Op.getOperand(1).getNode()) &&
+ ISD::isBuildVectorOfConstantSDNodes(Op.getOperand(2).getNode()))
+ return SDValue();
+
SDValue BlendOp = LowerVSELECTtoBlend(Op, Subtarget, DAG);
if (BlendOp.getNode())
return BlendOp;
SDValue BlendOp = LowerVSELECTtoBlend(Op, Subtarget, DAG);
if (BlendOp.getNode())
return BlendOp;
if (!ISD::isBuildVectorOfConstantSDNodes(Cond.getNode()))
return SDValue();
if (!ISD::isBuildVectorOfConstantSDNodes(Cond.getNode()))
return SDValue();
+ // A vselect where all conditions and data are constants can be optimized into
+ // a single vector load by SelectionDAGLegalize::ExpandBUILD_VECTOR().
+ if (ISD::isBuildVectorOfConstantSDNodes(LHS.getNode()) &&
+ ISD::isBuildVectorOfConstantSDNodes(RHS.getNode()))
+ return SDValue();
+
unsigned MaskValue = 0;
if (!BUILD_VECTORtoBlendMask(cast<BuildVectorSDNode>(Cond), MaskValue))
return SDValue();
unsigned MaskValue = 0;
if (!BUILD_VECTORtoBlendMask(cast<BuildVectorSDNode>(Cond), MaskValue))
return SDValue();
%1 = shufflevector <8 x i16> %a, <8 x i16> %b, <8 x i32> <i32 0, i32 9, i32 10, i32 3, i32 4, i32 5, i32 6, i32 15>
ret <8 x i16> %1
}
%1 = shufflevector <8 x i16> %a, <8 x i16> %b, <8 x i32> <i32 0, i32 9, i32 10, i32 3, i32 4, i32 5, i32 6, i32 15>
ret <8 x i16> %1
}
+
+; PR20648 - a blend of constants isn't really a blend; it's just a constant pool load.
+; CHECK-LABEL: @does_not_blend
+; CHECK: movaps
+; CHECK-NEXT: ret
+define <4 x i32> @does_not_blend() {
+ %select = select <4 x i1> <i1 1, i1 0, i1 0, i1 1>, <4 x i32> <i32 1, i32 1, i32 1, i32 1>, <4 x i32> <i32 2, i32 2, i32 2, i32 2>
+ ret <4 x i32> %select
+}
+