[PATCH] D151068: [Scalarizer] Fix for vector bitcasts of different element numbers

[Mikael Holmén via Phabricator via llvm-commits]

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[Scalarizer] Fix for vector bitcasts of different element numbers

When scalarizing bitcasts ScalarizerVisitor::visitBitCastInst divide the
input in three different cases:

1. same number of elements before and after
2. more elements after
3. less elements after

For the first case there is no problem, but for 2) the code only really
worked if we had the case
 <M x t1> -> <N*M x t2>
Similarly for 3), the code only made sense for
 <N*M x t1> -> <M x t2>

So e.g. if we get a bitcast like
 %bc94 = bitcast <6 x i64> %wide.vec to <8 x i48>, !dbg !157
ScalarizerVisitor::visitBitCastInst crashes with
 opt: ../lib/IR/Instructions.cpp:3447: static llvm::CastInst *llvm::CastInst::Create(Instruction::CastOps, llvm::Value *, llvm::Type *, const llvm::Twine &, llvm::Instruction *): Assertion `castIsValid(op, S, Ty) && "Invalid cast!"' failed.

With this patch, we now make the scalarizer just leave such a bitcast since
it's totally unclear what we should do with it anyway.

ScalarizerVisitor::visitBitCastInst already returned early for
non-FixedVectorType type vectors.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D151068

Files:
  llvm/lib/Transforms/Scalar/Scalarizer.cpp
  llvm/test/Transforms/Scalarizer/bitcast.ll

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