[PATCH] D154114: [SLP] Provide an universal interface for FixedVectorType::get. NFC.

[Han-Kuan Chen via Phabricator via llvm-commits]

HanKuanChen added a comment.

@aeubanks @nikic I will not add this in the commit message. It is too long.
Let's say we have a IR like this

  %in1 = getelementptr inbounds i32, ptr %in0, i64 1
  %in2 = getelementptr inbounds i32, ptr %in0, i64 2
  %in3 = getelementptr inbounds i32, ptr %in0, i64 3
  %v0 = load i32, ptr %in0, align 4
  %v1 = load i32, ptr %in1, align 4
  %v2 = load i32, ptr %in2, align 4
  %v3 = load i32, ptr %in3, align 4

SLP can make this into `load <4 x i32>, ptr %in0, align 4`. Using `FixedVectorType::get(i32, 4)` works well.
For revec, we have a IR like this

  %in1 = getelementptr inbounds i32, ptr %in0, i64 4
  %in2 = getelementptr inbounds i32, ptr %in0, i64 8
  %in3 = getelementptr inbounds i32, ptr %in0, i64 12
  %v0 = load <4 x i32>, ptr %in0, align 4
  %v1 = load <4 x i32>, ptr %in1, align 4
  %v2 = load <4 x i32>, ptr %in2, align 4
  %v3 = load <4 x i32>, ptr %in3, align 4

SLP can make this into `load <16 x i32>, ptr %in0, align 4`. But using `FixedVectorType::get(<4 x i32>, 4)` is incorrect. The actually function call should be `FixedVectorType::get(i32, 16)`.
To make scalar to vector and vector to vector work together, you need

  unsigned NumElements = 1;
  if (auto *VecTy = dyn_cast<FixedVectorType>(ScalarTy))
    NumElements = VecTy->getNumElements();
  FixedVectorType *VecTy = FixedVectorType::get(ScalarTy->getScalarType(), VF * NumElements);

If `FixedVectorType::get` occurs only few times, do in this way is better. But the fact is we need a function to wrap it.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D154114/new/

https://reviews.llvm.org/D154114