[llvm] [RISCV] Model Zvzip VPAIR shuffle costs (PR #227177)

[Min-Yih Hsu via llvm-commits]

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+//===-- RISCVVectorUtils.h - RISC-V vector utilities ------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines RISC-V vector utilities shared across the backend,
+// including helpers for recognizing shuffle masks supported by vector
+// permutation instructions.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIB_TARGET_RISCV_RISCVVECTORUTILS_H
+#define LLVM_LIB_TARGET_RISCV_RISCVVECTORUTILS_H
+
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/Support/MathExtras.h"
+
+namespace llvm {
+
+inline bool isAlternating(const std::array<std::pair<int, int>, 2> &SrcInfo,
+                          ArrayRef<int> Mask, unsigned Factor,
+                          bool RequiredPolarity) {
+  int NumElts = Mask.size();
+  for (const auto &[Idx, M] : enumerate(Mask)) {
+    if (M < 0)
+      continue;
+    int Src = M >= NumElts;
+    int Diff = (int)Idx - (M % NumElts);
+    bool C = Src == SrcInfo[1].first && Diff == SrcInfo[1].second;
+    assert(C != (Src == SrcInfo[0].first && Diff == SrcInfo[0].second) &&
+           "Must match exactly one of the two slides");
+    if (RequiredPolarity != (C == (Idx / Factor) % 2))
+      return false;
+  }
+  return true;
+}
+
+/// Given a shuffle which can be represented as a pair of two slides,
+/// see if it is a pair-even idiom.
+/// Pair-even is:
+/// vs2: a0 a1 a2 a3
+/// vs1: b0 b1 b2 b3
+/// vd:  a0 b0 a2 b2
+inline bool isPairEven(const std::array<std::pair<int, int>, 2> &SrcInfo,
+                       ArrayRef<int> Mask, unsigned &Factor) {
+  Factor = SrcInfo[1].second;
+  return SrcInfo[0].second == 0 && isPowerOf2_32(Factor) &&
+         Mask.size() % Factor == 0 &&
+         isAlternating(SrcInfo, Mask, Factor, true);
+}
+
+/// Given a shuffle which can be represented as a pair of two slides,
+/// see if it is a pair-odd idiom.
+/// Pair-odd is:
+/// vs2: a0 a1 a2 a3
+/// vs1: b0 b1 b2 b3
+/// vd:  a1 b1 a3 b3
+/// Note that the operand order is swapped due to the way we canonicalize
+/// the slides, so SrCInfo[0] is vs1, and SrcInfo[1] is vs2.
+inline bool isPairOdd(const std::array<std::pair<int, int>, 2> &SrcInfo,
+                      ArrayRef<int> Mask, unsigned &Factor) {
+  Factor = -SrcInfo[1].second;
+  return SrcInfo[0].second == 0 && isPowerOf2_32(Factor) &&
+         Mask.size() % Factor == 0 &&
+         isAlternating(SrcInfo, Mask, Factor, false);
+}
+} // end namespace llvm
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mshockwave wrote:

nit: I thought we only write "namespace llvm" nowadays

https://github.com/llvm/llvm-project/pull/227177