Extend MCAsmLexer so that it can peek forward several tokens

This commit adds a virtual `peekTokens()` function to `MCAsmLexer`
which can peek forward an arbitrary number of tokens.

It also makes the `peekTok()` method call `peekTokens()` method, but
only requesting one token.

The idea is to better support targets which more more ambiguous
assembly syntaxes.

Patch by Dylan McKay!

llvm-svn: 245221

3 files changed, 30 insertions, 5 deletions

diff --git a/llvm/include/llvm/MC/MCParser/AsmLexer.h b/llvm/include/llvm/MC/MCParser/AsmLexer.h
index 62d39b26c86..1bb6d212784 100644
--- a/llvm/include/llvm/MC/MCParser/AsmLexer.h
+++ b/llvm/include/llvm/MC/MCParser/AsmLexer.h
@@ -47,7 +47,8 @@ public:
   StringRef LexUntilEndOfStatement() override;
   StringRef LexUntilEndOfLine();
 
-  const AsmToken peekTok(bool ShouldSkipSpace = true) override;
+  size_t peekTokens(MutableArrayRef<AsmToken> Buf,
+                    bool ShouldSkipSpace = true) override;
 
   bool isAtStartOfComment(const char *Ptr);
   bool isAtStatementSeparator(const char *Ptr);
diff --git a/llvm/include/llvm/MC/MCParser/MCAsmLexer.h b/llvm/include/llvm/MC/MCParser/MCAsmLexer.h
index 71f15b37c33..644dbd90997 100644
--- a/llvm/include/llvm/MC/MCParser/MCAsmLexer.h
+++ b/llvm/include/llvm/MC/MCParser/MCAsmLexer.h
@@ -162,7 +162,21 @@ public:
   }
 
   /// Look ahead at the next token to be lexed.
-  virtual const AsmToken peekTok(bool ShouldSkipSpace = true) = 0;
+  const AsmToken peekTok(bool ShouldSkipSpace = true) {
+    AsmToken Tok;
+
+    MutableArrayRef<AsmToken> Buf(Tok);
+    size_t ReadCount = peekTokens(Buf, ShouldSkipSpace);
+
+    assert(ReadCount == 1);
+    (void)ReadCount;
+
+    return Tok;
+  }
+
+  /// Look ahead an arbitrary number of tokens.
+  virtual size_t peekTokens(MutableArrayRef<AsmToken> Buf,
+                            bool ShouldSkipSpace = true) = 0;
 
   /// Get the current error location
   const SMLoc &getErrLoc() {
diff --git a/llvm/lib/MC/MCParser/AsmLexer.cpp b/llvm/lib/MC/MCParser/AsmLexer.cpp
index b983d9995f4..36c19202685 100644
--- a/llvm/lib/MC/MCParser/AsmLexer.cpp
+++ b/llvm/lib/MC/MCParser/AsmLexer.cpp
@@ -436,7 +436,8 @@ StringRef AsmLexer::LexUntilEndOfLine() {
   return StringRef(TokStart, CurPtr-TokStart);
 }
 
-const AsmToken AsmLexer::peekTok(bool ShouldSkipSpace) {
+size_t AsmLexer::peekTokens(MutableArrayRef<AsmToken> Buf,
+                            bool ShouldSkipSpace) {
   const char *SavedTokStart = TokStart;
   const char *SavedCurPtr = CurPtr;
   bool SavedAtStartOfLine = isAtStartOfLine;
@@ -446,7 +447,16 @@ const AsmToken AsmLexer::peekTok(bool ShouldSkipSpace) {
   SMLoc SavedErrLoc = getErrLoc();
 
   SkipSpace = ShouldSkipSpace;
-  AsmToken Token = LexToken();
+
+  size_t ReadCount;
+  for (ReadCount = 0; ReadCount < Buf.size(); ++ReadCount) {
+    AsmToken Token = LexToken();
+
+    Buf[ReadCount] = Token;
+
+    if (Token.is(AsmToken::Eof))
+      break;
+  }
 
   SetError(SavedErrLoc, SavedErr);
 
@@ -455,7 +465,7 @@ const AsmToken AsmLexer::peekTok(bool ShouldSkipSpace) {
   CurPtr = SavedCurPtr;
   TokStart = SavedTokStart;
 
-  return Token;
+  return ReadCount;
 }
 
 bool AsmLexer::isAtStartOfComment(const char *Ptr) {