llvm/lib/Support/RISCVISAUtils.cpp

   1 //===-- RISCVISAUtils.cpp - RISC-V ISA Utilities --------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // Utilities shared by TableGen and RISCVISAInfo.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/Support/RISCVISAUtils.h"
  14 #include "llvm/ADT/StringExtras.h"
  15 #include <cassert>
  16
  17 using namespace llvm;
  18
  19 // We rank extensions in the following order:
  20 // -Single letter extensions in canonical order.
  21 // -Unknown single letter extensions in alphabetical order.
  22 // -Multi-letter extensions starting with 'z' sorted by canonical order of
  23 //  the second letter then sorted alphabetically.
  24 // -Multi-letter extensions starting with 's' in alphabetical order.
  25 // -(TODO) Multi-letter extensions starting with 'zxm' in alphabetical order.
  26 // -X extensions in alphabetical order.
  27 // -Unknown multi-letter extensions in alphabetical order.
  28 // These flags are used to indicate the category. The first 6 bits store the
  29 // single letter extension rank for single letter and multi-letter extensions
  30 // starting with 'z'.
  31 enum RankFlags {
  32   RF_Z_EXTENSION = 1 << 6,
  33   RF_S_EXTENSION = 2 << 6,
  34   RF_X_EXTENSION = 3 << 6,
  35   RF_UNKNOWN_MULTILETTER_EXTENSION = 4 << 6,
  36 };
  37
  38 // Get the rank for single-letter extension, lower value meaning higher
  39 // priority.
  40 static unsigned singleLetterExtensionRank(char Ext) {
  41   assert(isLower(Ext));
  42   switch (Ext) {
  43   case 'i':
  44     return 0;
  45   case 'e':
  46     return 1;
  47   }
  48
  49   size_t Pos = RISCVISAUtils::AllStdExts.find(Ext);
  50   if (Pos != StringRef::npos)
  51     return Pos + 2; // Skip 'e' and 'i' from above.
  52
  53   // If we got an unknown extension letter, then give it an alphabetical
  54   // order, but after all known standard extensions.
  55   return 2 + RISCVISAUtils::AllStdExts.size() + (Ext - 'a');
  56 }
  57
  58 // Get the rank for multi-letter extension, lower value meaning higher
  59 // priority/order in canonical order.
  60 static unsigned getExtensionRank(const std::string &ExtName) {
  61   assert(ExtName.size() >= 1);
  62   switch (ExtName[0]) {
  63   case 's':
  64     return RF_S_EXTENSION;
  65   case 'z':
  66     assert(ExtName.size() >= 2);
  67     // `z` extension must be sorted by canonical order of second letter.
  68     // e.g. zmx has higher rank than zax.
  69     return RF_Z_EXTENSION | singleLetterExtensionRank(ExtName[1]);
  70   case 'x':
  71     return RF_X_EXTENSION;
  72   default:
  73     if (ExtName.size() == 1)
  74       return singleLetterExtensionRank(ExtName[0]);
  75     return RF_UNKNOWN_MULTILETTER_EXTENSION;
  76   }
  77 }
  78
  79 // Compare function for extension.
  80 // Only compare the extension name, ignore version comparison.
  81 bool llvm::RISCVISAUtils::compareExtension(const std::string &LHS,
  82                                            const std::string &RHS) {
  83   unsigned LHSRank = getExtensionRank(LHS);
  84   unsigned RHSRank = getExtensionRank(RHS);
  85
  86   // If the ranks differ, pick the lower rank.
  87   if (LHSRank != RHSRank)
  88     return LHSRank < RHSRank;
  89
  90   // If the rank is same, it must be sorted by lexicographic order.
  91   return LHS < RHS;
  92 }