[GlobalISel] Change representation of shuffle masks in MachineOperand.

We're planning to remove the shufflemask operand from ShuffleVectorInst
(D72467); fix GlobalISel so it doesn't depend on that Constant.

The change to prelegalizercombiner-shuffle-vector.mir happens because
the input contains a literal "-1" in the mask (so the parser/verifier
weren't really handling it properly). We now treat it as equivalent to
"undef" in all contexts.

Differential Revision: https://reviews.llvm.org/D72663

3 files changed, 6 insertions, 7 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
index 3a7bf6d7378..a103e8e4e6e 100644
--- a/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
@@ -239,8 +239,7 @@ bool CombinerHelper::matchCombineShuffleVector(MachineInstr &MI,
   // vectors.
   unsigned NumConcat = DstNumElts / SrcNumElts;
   SmallVector<int, 8> ConcatSrcs(NumConcat, -1);
-  SmallVector<int, 8> Mask;
-  ShuffleVectorInst::getShuffleMask(MI.getOperand(3).getShuffleMask(), Mask);
+  ArrayRef<int> Mask = MI.getOperand(3).getShuffleMask();
   for (unsigned i = 0; i != DstNumElts; ++i) {
     int Idx = Mask[i];
     // Undef value.
diff --git a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
index df6a08b840d..17eca2b0301 100644
--- a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
@@ -1933,11 +1933,14 @@ bool IRTranslator::translateExtractElement(const User &U,
 
 bool IRTranslator::translateShuffleVector(const User &U,
                                           MachineIRBuilder &MIRBuilder) {
+  SmallVector<int, 8> Mask;
+  ShuffleVectorInst::getShuffleMask(cast<Constant>(U.getOperand(2)), Mask);
+  ArrayRef<int> MaskAlloc = MF->allocateShuffleMask(Mask);
   MIRBuilder.buildInstr(TargetOpcode::G_SHUFFLE_VECTOR)
       .addDef(getOrCreateVReg(U))
       .addUse(getOrCreateVReg(*U.getOperand(0)))
       .addUse(getOrCreateVReg(*U.getOperand(1)))
-      .addShuffleMask(cast<Constant>(U.getOperand(2)));
+      .addShuffleMask(MaskAlloc);
   return true;
 }
 
diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index 20f89abe03b..667e1a04dc3 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -4202,10 +4202,7 @@ LegalizerHelper::lowerShuffleVector(MachineInstr &MI) {
   LLT DstTy = MRI.getType(DstReg);
   LLT IdxTy = LLT::scalar(32);
 
-  const Constant *ShufMask = MI.getOperand(3).getShuffleMask();
-
-  SmallVector<int, 32> Mask;
-  ShuffleVectorInst::getShuffleMask(ShufMask, Mask);
+  ArrayRef<int> Mask = MI.getOperand(3).getShuffleMask();
 
   if (DstTy.isScalar()) {
     if (Src0Ty.isVector())