1 //===- MILexer.cpp - Machine instructions lexer implementation ----------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements the lexing of machine instructions.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "MILexer.h"
15 #include "llvm/ADT/Twine.h"
16 #include <cctype>
17 
18 using namespace llvm;
19 
20 namespace {
21 
22 /// This class provides a way to iterate and get characters from the source
23 /// string.
24 class Cursor {
25   const char *Ptr;
26   const char *End;
27 
28 public:
29   Cursor(NoneType) : Ptr(nullptr), End(nullptr) {}
30 
31   explicit Cursor(StringRef Str) {
32     Ptr = Str.data();
33     End = Ptr + Str.size();
34   }
35 
36   bool isEOF() const { return Ptr == End; }
37 
38   char peek(int I = 0) const { return End - Ptr <= I ? 0 : Ptr[I]; }
39 
40   void advance(unsigned I = 1) { Ptr += I; }
41 
42   StringRef remaining() const { return StringRef(Ptr, End - Ptr); }
43 
44   StringRef upto(Cursor C) const {
45     assert(C.Ptr >= Ptr && C.Ptr <= End);
46     return StringRef(Ptr, C.Ptr - Ptr);
47   }
48 
49   StringRef::iterator location() const { return Ptr; }
50 
51   operator bool() const { return Ptr != nullptr; }
52 };
53 
54 } // end anonymous namespace
55 
56 /// Skip the leading whitespace characters and return the updated cursor.
57 static Cursor skipWhitespace(Cursor C) {
58   while (isspace(C.peek()))
59     C.advance();
60   return C;
61 }
62 
63 static bool isIdentifierChar(char C) {
64   return isalpha(C) || isdigit(C) || C == '_' || C == '-' || C == '.';
65 }
66 
67 static Cursor maybeLexIdentifier(Cursor C, MIToken &Token) {
68   if (!isalpha(C.peek()) && C.peek() != '_')
69     return None;
70   auto Range = C;
71   while (isIdentifierChar(C.peek()))
72     C.advance();
73   auto Identifier = Range.upto(C);
74   Token = MIToken(Identifier == "_" ? MIToken::underscore : MIToken::Identifier,
75                   Identifier);
76   return C;
77 }
78 
79 static Cursor maybeLexMachineBasicBlock(
80     Cursor C, MIToken &Token,
81     function_ref<void(StringRef::iterator Loc, const Twine &)> ErrorCallback) {
82   if (!C.remaining().startswith("%bb."))
83     return None;
84   auto Range = C;
85   C.advance(4); // Skip '%bb.'
86   if (!isdigit(C.peek())) {
87     Token = MIToken(MIToken::Error, C.remaining());
88     ErrorCallback(C.location(), "expected a number after '%bb.'");
89     return C;
90   }
91   auto NumberRange = C;
92   while (isdigit(C.peek()))
93     C.advance();
94   StringRef Number = NumberRange.upto(C);
95   unsigned StringOffset = 4 + Number.size(); // Drop '%bb.<id>'
96   if (C.peek() == '.') {
97     C.advance(); // Skip '.'
98     ++StringOffset;
99     while (isIdentifierChar(C.peek()))
100       C.advance();
101   }
102   Token = MIToken(MIToken::MachineBasicBlock, Range.upto(C), APSInt(Number),
103                   StringOffset);
104   return C;
105 }
106 
107 static Cursor maybeLexRegister(Cursor C, MIToken &Token) {
108   if (C.peek() != '%')
109     return None;
110   auto Range = C;
111   C.advance(); // Skip '%'
112   while (isIdentifierChar(C.peek()))
113     C.advance();
114   Token = MIToken(MIToken::NamedRegister, Range.upto(C),
115                   /*StringOffset=*/1); // Drop the '%'
116   return C;
117 }
118 
119 static Cursor maybeLexGlobalValue(Cursor C, MIToken &Token) {
120   if (C.peek() != '@')
121     return None;
122   auto Range = C;
123   C.advance(); // Skip the '@'
124   // TODO: add support for quoted names.
125   if (!isdigit(C.peek())) {
126     while (isIdentifierChar(C.peek()))
127       C.advance();
128     Token = MIToken(MIToken::NamedGlobalValue, Range.upto(C),
129                     /*StringOffset=*/1); // Drop the '@'
130     return C;
131   }
132   auto NumberRange = C;
133   while (isdigit(C.peek()))
134     C.advance();
135   Token =
136       MIToken(MIToken::GlobalValue, Range.upto(C), APSInt(NumberRange.upto(C)));
137   return C;
138 }
139 
140 static Cursor maybeLexIntegerLiteral(Cursor C, MIToken &Token) {
141   if (!isdigit(C.peek()) && (C.peek() != '-' || !isdigit(C.peek(1))))
142     return None;
143   auto Range = C;
144   C.advance();
145   while (isdigit(C.peek()))
146     C.advance();
147   StringRef StrVal = Range.upto(C);
148   Token = MIToken(MIToken::IntegerLiteral, StrVal, APSInt(StrVal));
149   return C;
150 }
151 
152 static MIToken::TokenKind symbolToken(char C) {
153   switch (C) {
154   case ',':
155     return MIToken::comma;
156   case '=':
157     return MIToken::equal;
158   default:
159     return MIToken::Error;
160   }
161 }
162 
163 static Cursor maybeLexSymbol(Cursor C, MIToken &Token) {
164   auto Kind = symbolToken(C.peek());
165   if (Kind == MIToken::Error)
166     return None;
167   auto Range = C;
168   C.advance();
169   Token = MIToken(Kind, Range.upto(C));
170   return C;
171 }
172 
173 StringRef llvm::lexMIToken(
174     StringRef Source, MIToken &Token,
175     function_ref<void(StringRef::iterator Loc, const Twine &)> ErrorCallback) {
176   auto C = skipWhitespace(Cursor(Source));
177   if (C.isEOF()) {
178     Token = MIToken(MIToken::Eof, C.remaining());
179     return C.remaining();
180   }
181 
182   if (Cursor R = maybeLexIdentifier(C, Token))
183     return R.remaining();
184   if (Cursor R = maybeLexMachineBasicBlock(C, Token, ErrorCallback))
185     return R.remaining();
186   if (Cursor R = maybeLexRegister(C, Token))
187     return R.remaining();
188   if (Cursor R = maybeLexGlobalValue(C, Token))
189     return R.remaining();
190   if (Cursor R = maybeLexIntegerLiteral(C, Token))
191     return R.remaining();
192   if (Cursor R = maybeLexSymbol(C, Token))
193     return R.remaining();
194 
195   Token = MIToken(MIToken::Error, C.remaining());
196   ErrorCallback(C.location(),
197                 Twine("unexpected character '") + Twine(C.peek()) + "'");
198   return C.remaining();
199 }
200