[llvm] r209929 - Convert a vselect into a concat_vector if possible
Filipe Cabecinhas
me at filcab.net
Fri May 30 16:03:11 PDT 2014
Author: filcab
Date: Fri May 30 18:03:11 2014
New Revision: 209929
URL: http://llvm.org/viewvc/llvm-project?rev=209929&view=rev
Log:
Convert a vselect into a concat_vector if possible
Summary:
If both vector args to vselect are concat_vectors and the condition is
constant and picks half a vector from each argument, convert the vselect
into a concat_vectors.
Added a test.
The ConvertSelectToConcatVector is assuming it doesn't get vselects with
arguments of, for example, <undef, undef, true, true>. Those get taken
care of in the checks above its call.
Reviewers: nadav, delena, grosbach, hfinkel
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D3916
Modified:
llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
llvm/trunk/test/CodeGen/Generic/select.ll
llvm/trunk/test/CodeGen/X86/vselect.ll
Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=209929&r1=209928&r2=209929&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Fri May 30 18:03:11 2014
@@ -4592,6 +4592,56 @@ std::pair<SDValue, SDValue> SplitVSETCC(
return std::make_pair(Lo, Hi);
}
+// This function assumes all the vselect's arguments are CONCAT_VECTOR
+// nodes and that the condition is a BV of ConstantSDNodes (or undefs).
+static SDValue ConvertSelectToConcatVector(SDNode *N, SelectionDAG &DAG) {
+ SDLoc dl(N);
+ SDValue Cond = N->getOperand(0);
+ SDValue LHS = N->getOperand(1);
+ SDValue RHS = N->getOperand(2);
+ MVT VT = N->getSimpleValueType(0);
+ int NumElems = VT.getVectorNumElements();
+ assert(LHS.getOpcode() == ISD::CONCAT_VECTORS &&
+ RHS.getOpcode() == ISD::CONCAT_VECTORS &&
+ Cond.getOpcode() == ISD::BUILD_VECTOR);
+
+ // We're sure we have an even number of elements due to the
+ // concat_vectors we have as arguments to vselect.
+ // Skip BV elements until we find one that's not an UNDEF
+ // After we find an UNDEF element, keep looping until we get to half the
+ // length of the BV and see if all the non-undef nodes are the same.
+ ConstantSDNode *BottomHalf = nullptr;
+ for (int i = 0; i < NumElems / 2; ++i) {
+ if (Cond->getOperand(i)->getOpcode() == ISD::UNDEF)
+ continue;
+
+ if (BottomHalf == nullptr)
+ BottomHalf = cast<ConstantSDNode>(Cond.getOperand(i));
+ else if (Cond->getOperand(i).getNode() != BottomHalf)
+ return SDValue();
+ }
+
+ // Do the same for the second half of the BuildVector
+ ConstantSDNode *TopHalf = nullptr;
+ for (int i = NumElems / 2; i < NumElems; ++i) {
+ if (Cond->getOperand(i)->getOpcode() == ISD::UNDEF)
+ continue;
+
+ if (TopHalf == nullptr)
+ TopHalf = cast<ConstantSDNode>(Cond.getOperand(i));
+ else if (Cond->getOperand(i).getNode() != TopHalf)
+ return SDValue();
+ }
+
+ assert(TopHalf && BottomHalf &&
+ "One half of the selector was all UNDEFs and the other was all the "
+ "same value. This should have been addressed before this function.");
+ return DAG.getNode(
+ ISD::CONCAT_VECTORS, dl, VT,
+ BottomHalf->isNullValue() ? RHS->getOperand(0) : LHS->getOperand(0),
+ TopHalf->isNullValue() ? RHS->getOperand(1) : LHS->getOperand(1));
+}
+
SDValue DAGCombiner::visitVSELECT(SDNode *N) {
SDValue N0 = N->getOperand(0);
SDValue N1 = N->getOperand(1);
@@ -4664,6 +4714,17 @@ SDValue DAGCombiner::visitVSELECT(SDNode
if (ISD::isBuildVectorAllZeros(N0.getNode()))
return N2;
+ // The ConvertSelectToConcatVector function is assuming both the above
+ // checks for (vselect (build_vector all{ones,zeros) ...) have been made
+ // and addressed.
+ if (N1.getOpcode() == ISD::CONCAT_VECTORS &&
+ N2.getOpcode() == ISD::CONCAT_VECTORS &&
+ ISD::isBuildVectorOfConstantSDNodes(N0.getNode())) {
+ SDValue CV = ConvertSelectToConcatVector(N, DAG);
+ if (CV.getNode())
+ return CV;
+ }
+
return SDValue();
}
Modified: llvm/trunk/test/CodeGen/Generic/select.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/Generic/select.ll?rev=209929&r1=209928&r2=209929&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/Generic/select.ll (original)
+++ llvm/trunk/test/CodeGen/Generic/select.ll Fri May 30 18:03:11 2014
@@ -192,4 +192,3 @@ define <1 x i32> @checkScalariseVSELECT(
%s = select <1 x i1> %cond, <1 x i32> %a, <1 x i32> %b
ret <1 x i32> %s
}
-
Modified: llvm/trunk/test/CodeGen/X86/vselect.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/vselect.ll?rev=209929&r1=209928&r2=209929&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/vselect.ll (original)
+++ llvm/trunk/test/CodeGen/X86/vselect.ll Fri May 30 18:03:11 2014
@@ -262,3 +262,17 @@ define <2 x i64> @test25(<2 x i64> %a, <
; CHECK: movsd
; CHECK: ret
+define <4 x float> @select_of_shuffles_0(<2 x float> %a0, <2 x float> %b0, <2 x float> %a1, <2 x float> %b1) {
+; CHECK-LABEL: select_of_shuffles_0
+; CHECK-DAG: movlhps %xmm2, [[REGA:%xmm[0-9]+]]
+; CHECK-DAG: movlhps %xmm3, [[REGB:%xmm[0-9]+]]
+; CHECK: subps [[REGB]], [[REGA]]
+ %1 = shufflevector <2 x float> %a0, <2 x float> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
+ %2 = shufflevector <2 x float> %a1, <2 x float> undef, <4 x i32> <i32 undef, i32 undef, i32 0, i32 1>
+ %3 = select <4 x i1> <i1 false, i1 false, i1 true, i1 true>, <4 x float> %2, <4 x float> %1
+ %4 = shufflevector <2 x float> %b0, <2 x float> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
+ %5 = shufflevector <2 x float> %b1, <2 x float> undef, <4 x i32> <i32 undef, i32 undef, i32 0, i32 1>
+ %6 = select <4 x i1> <i1 false, i1 false, i1 true, i1 true>, <4 x float> %5, <4 x float> %4
+ %7 = fsub <4 x float> %3, %6
+ ret <4 x float> %7
+}
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