Subzero: Initial O2 lowering

src/IceGlobalContext.cpp

 //===- subzero/src/IceGlobalContext.cpp - Global context defs ---*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file defines aspects of the compilation that persist across
@@ skipping 111 matching lines @@
     //   (splice in "6Prefix")          ^^^^^^^
     snprintf(NewName, BufLen, "_ZN%u%s%s", PrefixLength,
              getTestPrefix().c_str(), NameBase);
     // We ignore the snprintf return value (here and below).  If we
     // somehow miscalculated the output buffer length, the output will
     // be truncated, but it will be truncated consistently for all
     // mangleName() calls on the same input string.
     return NewName;
   }
 
-  ItemsParsed = sscanf(Name.c_str(), "_Z%u%s", &BaseLength, NameBase);
+  // Artificially limit BaseLength to 9 digits (less than 1 billion)
+  // because sscanf behavior is undefined on integer overflow.

[JF, 2014/05/25 22:50:50]

Add an assert that has this comment.

[Jim Stichnoth, 2014/05/29 01:39:46]

An assert isn't appropriate here.  The idea is to try to demangle a C++ symbol
involving a namespace, and if that fails, fall back to adding a prefix to a
presumed C symbol.  (There is one test in mangle.ll that tests for such integer
overflow.)

I updated the comment, and also tried to improve the overflow check by testing
whether the following string starts with a digit.

+  ItemsParsed = sscanf(Name.c_str(), "_Z%9u%s", &BaseLength, NameBase);
   if (ItemsParsed == 2 && BaseLength <= strlen(NameBase)) {
     // Transform _Z3barxyz ==> _ZN6Prefix3barExyz
     //                           ^^^^^^^^    ^
     // (splice in "N6Prefix", and insert "E" after "3bar")
     // But an "I" after the identifier indicates a template argument
     // list terminated with "E"; insert the new "E" before/after the
     // old "E".  E.g.:
     // Transform _Z3barIabcExyz ==> _ZN6Prefix3barIabcEExyz
     //                                ^^^^^^^^         ^
     // (splice in "N6Prefix", and insert "E" after "3barIabcE")
@@ skipping 61 matching lines @@
 
 void Timer::printElapsedUs(GlobalContext *Ctx, const IceString &Tag) const {
   if (Ctx->isVerbose(IceV_Timing)) {
     // Prefixing with '#' allows timing strings to be included
     // without error in textual assembly output.
     Ctx->getStrDump() << "# " << getElapsedUs() << " usec " << Tag << "\n";
   }
 }
 
 } // end of namespace Ice