[GISel][CombinerHelper] Combine shuffle_vector scalar to build_vector

Teach the combiner helper how to replace shuffle_vector of scalars
into build_vector.
I am not particularly happy about having to add this combine, but we
currently get those from <1 x iN> from the IR.

Bonus: This fixes an assert in the shuffle_vector combines since before
this patch, we were expecting vector types.

1 files changed, 2 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
index 854769d283f..bb7f751de90 100644
--- a/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
@@ -190,7 +190,7 @@ bool CombinerHelper::matchCombineShuffleVector(MachineInstr &MI,
   Register Src1 = MI.getOperand(1).getReg();
   LLT SrcType = MRI.getType(Src1);
   unsigned DstNumElts = DstType.getNumElements();
-  unsigned SrcNumElts = SrcType.getNumElements();
+  unsigned SrcNumElts = SrcType.isVector() ? SrcType.getNumElements() : 1;
 
   // If the resulting vector is smaller than the size of the source
   // vectors being concatenated, we won't be able to replace the
@@ -254,7 +254,7 @@ void CombinerHelper::applyCombineShuffleVector(MachineInstr &MI,
   Builder.setInsertPt(*MI.getParent(), MI);
   Register NewDstReg = MRI.cloneVirtualRegister(DstReg);
 
-  Builder.buildConcatVectors(NewDstReg, Ops);
+  Builder.buildMerge(NewDstReg, Ops);
 
   MI.eraseFromParent();
   replaceRegWith(MRI, DstReg, NewDstReg);