[llvm] [RISCV] Separate the analysis part of RISCVInsertVSETVLI. (PR #149574)

[Min-Yih Hsu via llvm-commits]

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+//===- RISCVVectorConfigAnalysis ------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+/// \file
+/// This is the RISCV analysis of vector unit config.
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIB_TARGET_RISCV_RISCVVCONFIGANALYSIS_H
+#define LLVM_LIB_TARGET_RISCV_RISCVVCONFIGANALYSIS_H
+
+#include "RISCV.h"
+#include "RISCVSubtarget.h"
+#include "llvm/CodeGen/LiveIntervals.h"
+#include "llvm/CodeGen/LiveStacks.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachinePassManager.h"
+#include <queue>
+#include <vector>
+using namespace llvm;
+
+namespace llvm {
+/// Which subfields of VL or VTYPE have values we need to preserve?
+struct DemandedFields {
+  // Some unknown property of VL is used.  If demanded, must preserve entire
+  // value.
+  bool VLAny = false;
+  // Only zero vs non-zero is used. If demanded, can change non-zero values.
+  bool VLZeroness = false;
+  // What properties of SEW we need to preserve.
+  enum : uint8_t {
+    SEWEqual = 3, // The exact value of SEW needs to be preserved.
+    SEWGreaterThanOrEqualAndLessThan64 =
+        2, // SEW can be changed as long as it's greater
+           // than or equal to the original value, but must be less
+           // than 64.
+    SEWGreaterThanOrEqual = 1, // SEW can be changed as long as it's greater
+                               // than or equal to the original value.
+    SEWNone = 0                // We don't need to preserve SEW at all.
+  } SEW = SEWNone;
+  enum : uint8_t {
+    LMULEqual = 2, // The exact value of LMUL needs to be preserved.
+    LMULLessThanOrEqualToM1 = 1, // We can use any LMUL <= M1.
+    LMULNone = 0                 // We don't need to preserve LMUL at all.
+  } LMUL = LMULNone;
+  bool SEWLMULRatio = false;
+  bool TailPolicy = false;
+  bool MaskPolicy = false;
+  // If this is true, we demand that VTYPE is set to some legal state, i.e. that
+  // vill is unset.
+  bool VILL = false;
+
+  // Return true if any part of VTYPE was used
+  bool usedVTYPE() const {
+    return SEW || LMUL || SEWLMULRatio || TailPolicy || MaskPolicy || VILL;
+  }
+
+  // Return true if any property of VL was used
+  bool usedVL() { return VLAny || VLZeroness; }
+
+  // Mark all VTYPE subfields and properties as demanded
+  void demandVTYPE() {
+    SEW = SEWEqual;
+    LMUL = LMULEqual;
+    SEWLMULRatio = true;
+    TailPolicy = true;
+    MaskPolicy = true;
+    VILL = true;
+  }
+
+  // Mark all VL properties as demanded
+  void demandVL() {
+    VLAny = true;
+    VLZeroness = true;
+  }
+
+  static DemandedFields all() {
+    DemandedFields DF;
+    DF.demandVTYPE();
+    DF.demandVL();
+    return DF;
+  }
+
+  // Make this the result of demanding both the fields in this and B.
+  void doUnion(const DemandedFields &B) {
+    VLAny |= B.VLAny;
+    VLZeroness |= B.VLZeroness;
+    SEW = std::max(SEW, B.SEW);
+    LMUL = std::max(LMUL, B.LMUL);
+    SEWLMULRatio |= B.SEWLMULRatio;
+    TailPolicy |= B.TailPolicy;
+    MaskPolicy |= B.MaskPolicy;
+    VILL |= B.VILL;
+  }
+
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+  /// Support for debugging, callable in GDB: V->dump()
+  LLVM_DUMP_METHOD void dump() const {
+    print(dbgs());
+    dbgs() << "\n";
+  }
+
+  /// Implement operator<<.
+  void print(raw_ostream &OS) const {
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mshockwave wrote:

nit: this function body is relatively big...maybe putting it in the .cpp file?

https://github.com/llvm/llvm-project/pull/149574