[llvm] r295152 - [SelectionDAGBuilder] Simplify creation of shufflevector DAG nodes where inputs are larger than the mask
Craig Topper via llvm-commits
llvm-commits at lists.llvm.org
Tue Feb 14 21:57:16 PST 2017
Author: ctopper
Date: Tue Feb 14 23:57:16 2017
New Revision: 295152
URL: http://llvm.org/viewvc/llvm-project?rev=295152&view=rev
Log:
[SelectionDAGBuilder] Simplify creation of shufflevector DAG nodes where inputs are larger than the mask
Summary:
The current code loops over all elements to calculate a used range. Then a second short loop looks at the ranges and determines if they can be used in a extract and creates a properly aligned start index for the extract.
This range finding is unnecessary, we can just calculate a properly aligned start index for an extract for each input during the first loop. If we don't find the same start index for each indice we can't use an extract.
Reviewers: zvi, RKSimon
Reviewed By: zvi
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D29926
Modified:
llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp?rev=295152&r1=295151&r2=295152&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp Tue Feb 14 23:57:16 2017
@@ -3104,14 +3104,10 @@ void SelectionDAGBuilder::visitShuffleVe
if (SrcNumElts > MaskNumElts) {
// Analyze the access pattern of the vector to see if we can extract
- // two subvectors and do the shuffle. The analysis is done by calculating
- // the range of elements the mask access on both vectors.
- int MinRange[2] = { static_cast<int>(SrcNumElts),
- static_cast<int>(SrcNumElts)};
- int MaxRange[2] = {-1, -1};
-
- for (unsigned i = 0; i != MaskNumElts; ++i) {
- int Idx = Mask[i];
+ // two subvectors and do the shuffle.
+ int StartIdx[2] = { -1, -1 }; // StartIdx to extract from
+ bool CanExtract = true;
+ for (int Idx : Mask) {
unsigned Input = 0;
if (Idx < 0)
continue;
@@ -3120,41 +3116,28 @@ void SelectionDAGBuilder::visitShuffleVe
Input = 1;
Idx -= SrcNumElts;
}
- if (Idx > MaxRange[Input])
- MaxRange[Input] = Idx;
- if (Idx < MinRange[Input])
- MinRange[Input] = Idx;
- }
-
- // Check if the access is smaller than the vector size and can we find
- // a reasonable extract index.
- int RangeUse[2] = { -1, -1 }; // 0 = Unused, 1 = Extract, -1 = Can not
- // Extract.
- int StartIdx[2]; // StartIdx to extract from
- for (unsigned Input = 0; Input < 2; ++Input) {
- if (MinRange[Input] >= (int)SrcNumElts && MaxRange[Input] < 0) {
- RangeUse[Input] = 0; // Unused
- StartIdx[Input] = 0;
- continue;
- }
- // Find a good start index that is a multiple of the mask length. Then
- // see if the rest of the elements are in range.
- StartIdx[Input] = (MinRange[Input]/MaskNumElts)*MaskNumElts;
- if (MaxRange[Input] - StartIdx[Input] < (int)MaskNumElts &&
- StartIdx[Input] + MaskNumElts <= SrcNumElts)
- RangeUse[Input] = 1; // Extract from a multiple of the mask length.
+ // If all the indices come from the same MaskNumElts sized portion of
+ // the sources we can use extract. Also make sure the extract wouldn't
+ // extract past the end of the source.
+ int NewStartIdx = alignDown(Idx, MaskNumElts);
+ if (NewStartIdx + MaskNumElts > SrcNumElts ||
+ (StartIdx[Input] >= 0 && StartIdx[Input] != NewStartIdx))
+ CanExtract = false;
+ // Make sure we always update StartIdx as we use it to track if all
+ // elements are undef.
+ StartIdx[Input] = NewStartIdx;
}
- if (RangeUse[0] == 0 && RangeUse[1] == 0) {
+ if (StartIdx[0] < 0 && StartIdx[1] < 0) {
setValue(&I, DAG.getUNDEF(VT)); // Vectors are not used.
return;
}
- if (RangeUse[0] >= 0 && RangeUse[1] >= 0) {
+ if (CanExtract) {
// Extract appropriate subvector and generate a vector shuffle
for (unsigned Input = 0; Input < 2; ++Input) {
SDValue &Src = Input == 0 ? Src1 : Src2;
- if (RangeUse[Input] == 0)
+ if (StartIdx[Input] < 0)
Src = DAG.getUNDEF(VT);
else {
Src = DAG.getNode(
@@ -3165,16 +3148,12 @@ void SelectionDAGBuilder::visitShuffleVe
}
// Calculate new mask.
- SmallVector<int, 8> MappedOps;
- for (unsigned i = 0; i != MaskNumElts; ++i) {
- int Idx = Mask[i];
- if (Idx >= 0) {
- if (Idx < (int)SrcNumElts)
- Idx -= StartIdx[0];
- else
- Idx -= SrcNumElts + StartIdx[1] - MaskNumElts;
- }
- MappedOps.push_back(Idx);
+ SmallVector<int, 8> MappedOps(Mask.begin(), Mask.end());
+ for (int &Idx : MappedOps) {
+ if (Idx >= (int)SrcNumElts)
+ Idx -= SrcNumElts + StartIdx[1] - MaskNumElts;
+ else if (Idx >= 0)
+ Idx -= StartIdx[0];
}
setValue(&I, DAG.getVectorShuffle(VT, DL, Src1, Src2, MappedOps));
@@ -3188,8 +3167,7 @@ void SelectionDAGBuilder::visitShuffleVe
EVT EltVT = VT.getVectorElementType();
EVT IdxVT = TLI.getVectorIdxTy(DAG.getDataLayout());
SmallVector<SDValue,8> Ops;
- for (unsigned i = 0; i != MaskNumElts; ++i) {
- int Idx = Mask[i];
+ for (int Idx : Mask) {
SDValue Res;
if (Idx < 0) {
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