GlobalISel: Implement fewerElementsVector for G_BUILD_VECTOR
Turn it into a G_CONCAT_VECTORS of G_BUILD_VECTOR.
llvm-svn: 374252
diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index 684b99d..c5830ff 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -2767,6 +2767,65 @@
}
LegalizerHelper::LegalizeResult
+LegalizerHelper::fewerElementsVectorBuildVector(MachineInstr &MI,
+ unsigned TypeIdx,
+ LLT NarrowTy) {
+ assert(TypeIdx == 0 && "not a vector type index");
+ Register DstReg = MI.getOperand(0).getReg();
+ LLT DstTy = MRI.getType(DstReg);
+ LLT SrcTy = DstTy.getElementType();
+
+ int DstNumElts = DstTy.getNumElements();
+ int NarrowNumElts = NarrowTy.getNumElements();
+ int NumConcat = (DstNumElts + NarrowNumElts - 1) / NarrowNumElts;
+ LLT WidenedDstTy = LLT::vector(NarrowNumElts * NumConcat, SrcTy);
+
+ SmallVector<Register, 8> ConcatOps;
+ SmallVector<Register, 8> SubBuildVector;
+
+ Register UndefReg;
+ if (WidenedDstTy != DstTy)
+ UndefReg = MIRBuilder.buildUndef(SrcTy).getReg(0);
+
+ // Create a G_CONCAT_VECTORS of NarrowTy pieces, padding with undef as
+ // necessary.
+ //
+ // %3:_(<3 x s16>) = G_BUILD_VECTOR %0, %1, %2
+ // -> <2 x s16>
+ //
+ // %4:_(s16) = G_IMPLICIT_DEF
+ // %5:_(<2 x s16>) = G_BUILD_VECTOR %0, %1
+ // %6:_(<2 x s16>) = G_BUILD_VECTOR %2, %4
+ // %7:_(<4 x s16>) = G_CONCAT_VECTORS %5, %6
+ // %3:_(<3 x s16>) = G_EXTRACT %7, 0
+ for (int I = 0; I != NumConcat; ++I) {
+ for (int J = 0; J != NarrowNumElts; ++J) {
+ int SrcIdx = NarrowNumElts * I + J;
+
+ if (SrcIdx < DstNumElts) {
+ Register SrcReg = MI.getOperand(SrcIdx + 1).getReg();
+ SubBuildVector.push_back(SrcReg);
+ } else
+ SubBuildVector.push_back(UndefReg);
+ }
+
+ auto BuildVec = MIRBuilder.buildBuildVector(NarrowTy, SubBuildVector);
+ ConcatOps.push_back(BuildVec.getReg(0));
+ SubBuildVector.clear();
+ }
+
+ if (DstTy == WidenedDstTy)
+ MIRBuilder.buildConcatVectors(DstReg, ConcatOps);
+ else {
+ auto Concat = MIRBuilder.buildConcatVectors(WidenedDstTy, ConcatOps);
+ MIRBuilder.buildExtract(DstReg, Concat, 0);
+ }
+
+ MI.eraseFromParent();
+ return Legalized;
+}
+
+LegalizerHelper::LegalizeResult
LegalizerHelper::reduceLoadStoreWidth(MachineInstr &MI, unsigned TypeIdx,
LLT NarrowTy) {
// FIXME: Don't know how to handle secondary types yet.
@@ -2941,6 +3000,8 @@
return fewerElementsVectorPhi(MI, TypeIdx, NarrowTy);
case G_UNMERGE_VALUES:
return fewerElementsVectorUnmergeValues(MI, TypeIdx, NarrowTy);
+ case G_BUILD_VECTOR:
+ return fewerElementsVectorBuildVector(MI, TypeIdx, NarrowTy);
case G_LOAD:
case G_STORE:
return reduceLoadStoreWidth(MI, TypeIdx, NarrowTy);