GlobalISel: Implement fewerElements for implicit_def

llvm-svn: 350697

2 files changed, 41 insertions, 3 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index c6e5f3e6124..34b466a41d2 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -1172,6 +1172,32 @@ LegalizerHelper::fewerElementsVector(MachineInstr &MI, unsigned TypeIdx,
   switch (MI.getOpcode()) {
   default:
     return UnableToLegalize;
+  case TargetOpcode::G_IMPLICIT_DEF: {
+    SmallVector<unsigned, 2> DstRegs;
+
+    unsigned NarrowSize = NarrowTy.getSizeInBits();
+    unsigned DstReg = MI.getOperand(0).getReg();
+    unsigned Size = MRI.getType(DstReg).getSizeInBits();
+    int NumParts = Size / NarrowSize;
+    // FIXME: Don't know how to handle the situation where the small vectors
+    // aren't all the same size yet.
+    if (Size % NarrowSize != 0)
+      return UnableToLegalize;
+
+    for (int i = 0; i < NumParts; ++i) {
+      unsigned TmpReg = MRI.createGenericVirtualRegister(NarrowTy);
+      MIRBuilder.buildUndef(TmpReg);
+      DstRegs.push_back(TmpReg);
+    }
+
+    if (NarrowTy.isVector())
+      MIRBuilder.buildConcatVectors(DstReg, DstRegs);
+    else
+      MIRBuilder.buildBuildVector(DstReg, DstRegs);
+
+    MI.eraseFromParent();
+    return Legalized;
+  }
   case TargetOpcode::G_ADD: {
     unsigned NarrowSize = NarrowTy.getSizeInBits();
     unsigned DstReg = MI.getOperand(0).getReg();
diff --git a/llvm/lib/Target/AArch64/AArch64LegalizerInfo.cpp b/llvm/lib/Target/AArch64/AArch64LegalizerInfo.cpp
index 91b3fe2c7d3..6f7fb7a8bc2 100644
--- a/llvm/lib/Target/AArch64/AArch64LegalizerInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64LegalizerInfo.cpp
@@ -48,9 +48,21 @@ AArch64LegalizerInfo::AArch64LegalizerInfo(const AArch64Subtarget &ST) {
   const LLT v2s64 = LLT::vector(2, 64);
 
   getActionDefinitionsBuilder(G_IMPLICIT_DEF)
-      .legalFor({p0, s1, s8, s16, s32, s64, v2s64})
-      .clampScalar(0, s1, s64)
-      .widenScalarToNextPow2(0, 8);
+    .legalFor({p0, s1, s8, s16, s32, s64, v2s64})
+    .clampScalar(0, s1, s64)
+    .widenScalarToNextPow2(0, 8)
+    .fewerElementsIf(
+      [=](const LegalityQuery &Query) {
+        return Query.Types[0].isVector() &&
+          (Query.Types[0].getElementType() != s64 ||
+           Query.Types[0].getNumElements() != 2);
+      },
+      [=](const LegalityQuery &Query) {
+        LLT EltTy = Query.Types[0].getElementType();
+        if (EltTy == s64)
+          return std::make_pair(0, LLT::vector(2, 64));
+        return std::make_pair(0, EltTy);
+      });
 
   getActionDefinitionsBuilder(G_PHI)
       .legalFor({p0, s16, s32, s64})