[lld] r228077 - Simplify large switches.

[Rui Ueyama]

I know everybody has his or her own taste, but I was honestly a bit
surprised that you said the original code was more readable. It's at least
neutral, I believe. And it's shorter. This patch saved vertical space in
your editor.

This is different from the lexer's main switch statement (Lexer::lex still
consists of one gigantic switch). These are predicate functions for a
character; if a given character is a member of a set, return true.
Otherwise false. The new functions just do that with a far fewer lines of
code.


On Tue, Feb 3, 2015 at 6:33 PM, Shankar Easwaran <shankare at codeaurora.org>
wrote:

> The style used in the old code is followed in clang too in various places.
> I felt its more readable too.
>
> This makes it less performant even if its not in performance critical pass
> and less readable too.
>
> Shankar Easwaran
>
>
> On 2/3/2015 6:00 PM, Rui Ueyama wrote:
>
>> Author: ruiu
>> Date: Tue Feb  3 18:00:21 2015
>> New Revision: 228077
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=228077&view=rev
>> Log:
>> Simplify large switches.
>>
>> This may be a little bit inefficient than the original code
>> but that should be okay as this is not really in a performance
>> critical pass.
>>
>> http://reviews.llvm.org/D7393
>>
>> Modified:
>>      lld/trunk/lib/ReaderWriter/LinkerScript.cpp
>>
>> Modified: lld/trunk/lib/ReaderWriter/LinkerScript.cpp
>> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/lib/
>> ReaderWriter/LinkerScript.cpp?rev=228077&r1=228076&r2=228077&view=diff
>> ============================================================
>> ==================
>> --- lld/trunk/lib/ReaderWriter/LinkerScript.cpp (original)
>> +++ lld/trunk/lib/ReaderWriter/LinkerScript.cpp Tue Feb  3 18:00:21 2015
>> @@ -242,66 +242,17 @@ bool Lexer::canStartNumber(char c) const
>>   }
>>     bool Lexer::canContinueNumber(char c) const {
>> -  switch (c) {
>> -  // Digits
>> -  case '0': case '1': case '2': case '3': case '4': case '5': case '6':
>> -  case '7': case '8': case '9':
>> -  case 'A': case 'B': case 'C': case 'D': case 'E': case 'F':
>> -  case 'a': case 'b': case 'c': case 'd': case 'e': case 'f':
>> -  // Hex marker
>> -  case 'x': case 'X':
>> -  // Type suffix
>> -  case 'h': case 'H': case 'o': case 'O':
>> -  // Scale suffix
>> -  case 'M': case 'K':
>> -    return true;
>> -  default:
>> -    return false;
>> -  }
>> +  return strchr("0123456789ABCDEFabcdefxXhHoOMK", c);
>>   }
>>     bool Lexer::canStartName(char c) const {
>> -  switch (c) {
>> -  case 'A': case 'B': case 'C': case 'D': case 'E': case 'F': case 'G':
>> -  case 'H': case 'I': case 'J': case 'K': case 'L': case 'M': case 'N':
>> -  case 'O': case 'P': case 'Q': case 'R': case 'S': case 'T': case 'U':
>> -  case 'V': case 'W': case 'X': case 'Y': case 'Z':
>> -  case 'a': case 'b': case 'c': case 'd': case 'e': case 'f': case 'g':
>> -  case 'h': case 'i': case 'j': case 'k': case 'l': case 'm': case 'n':
>> -  case 'o': case 'p': case 'q': case 'r': case 's': case 't': case 'u':
>> -  case 'v': case 'w': case 'x': case 'y': case 'z':
>> -  case '_': case '.': case '$': case '/': case '\\':
>> -  case '*':
>> -    return true;
>> -  default:
>> -    return false;
>> -  }
>> +  return strchr(
>> +    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz_.$/\\*", c);
>>   }
>>     bool Lexer::canContinueName(char c) const {
>> -  switch (c) {
>> -  case 'A': case 'B': case 'C': case 'D': case 'E': case 'F': case 'G':
>> -  case 'H': case 'I': case 'J': case 'K': case 'L': case 'M': case 'N':
>> -  case 'O': case 'P': case 'Q': case 'R': case 'S': case 'T': case 'U':
>> -  case 'V': case 'W': case 'X': case 'Y': case 'Z':
>> -  case 'a': case 'b': case 'c': case 'd': case 'e': case 'f': case 'g':
>> -  case 'h': case 'i': case 'j': case 'k': case 'l': case 'm': case 'n':
>> -  case 'o': case 'p': case 'q': case 'r': case 's': case 't': case 'u':
>> -  case 'v': case 'w': case 'x': case 'y': case 'z':
>> -  case '0': case '1': case '2': case '3': case '4': case '5': case '6':
>> -  case '7': case '8': case '9':
>> -  case '_': case '.': case '$': case '/': case '\\': case '~': case '=':
>> -  case '+':
>> -  case '[':
>> -  case ']':
>> -  case '*':
>> -  case '?':
>> -  case '-':
>> -  case ':':
>> -    return true;
>> -  default:
>> -    return false;
>> -  }
>> +  return strchr("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
>> +                "0123456789_.$/\\~=+[]*?-:", c);
>>   }
>>     /// Helper function to split a StringRef in two at the nth character.
>>
>>
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>>
>
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