diff options
| -rw-r--r-- | tools/lto/LTOCodeGenerator.h | 45 |
1 files changed, 44 insertions, 1 deletions
diff --git a/tools/lto/LTOCodeGenerator.h b/tools/lto/LTOCodeGenerator.h index bbe3239..9c0e6c5 100644 --- a/tools/lto/LTOCodeGenerator.h +++ b/tools/lto/LTOCodeGenerator.h @@ -9,6 +9,27 @@ // // This file declares the LTOCodeGenerator class. // +// LTO compilation consists of three phases: Pre-IPO, IPO and Post-IPO. +// +// The Pre-IPO phase compiles source code into bitcode file. The resulting +// bitcode files, along with object files and libraries, will be fed to the +// linker to through the IPO and Post-IPO phases. By using obj-file extension, +// the resulting bitcode file disguises itself as an object file, and therefore +// obviates the need of writing a special set of the make-rules only for LTO +// compilation. +// +// The IPO phase perform inter-procedural analyses and optimizations, and +// the Post-IPO consists two sub-phases: intra-procedural scalar optimizations +// (SOPT), and intra-procedural target-dependent code generator (CG). +// +// As of this writing, we don't separate IPO and the Post-IPO SOPT. They +// are intermingled together, and are driven by a single pass manager (see +// PassManagerBuilder::populateLTOPassManager()). +// +// The "LTOCodeGenerator" is the driver for the IPO and Post-IPO stages. +// The "CodeGenerator" here is bit confusing. Don't confuse the "CodeGenerator" +// with the machine specific code generator. +// //===----------------------------------------------------------------------===// #ifndef LTO_CODE_GENERATOR_H @@ -50,10 +71,32 @@ struct LTOCodeGenerator { _mustPreserveSymbols[sym] = 1; } + // To pass options to the driver and optimization passes. These options are + // not necessarily for debugging purpose (The function name is misleading). + // This function should be called before LTOCodeGenerator::compilexxx(), + // and LTOCodeGenerator::writeMergedModules(). + // + void setCodeGenDebugOptions(const char *opts); + bool writeMergedModules(const char *path, std::string &errMsg); + + // Compile the merged module into a *single* object file; the path to object + // file is returned to the caller via argument "name". Return *FALSE* on + // *SUCCESS*, true otherwise. + // + // NOTE that it is up to the linker to remove the intermediate object file. + // Do not try to remove the object file in LTOCodeGenerator's destructor + // as we don't who (LTOCodeGenerator or the obj file) will last longer. + // bool compile_to_file(const char **name, std::string &errMsg); + + // As with compile_to_file(), this function compiles the merged module into + // single object file. Instead of returning the object-file-path to the caller + // (linker), it brings the object to a buffer, and return the buffer to the + // caller. This function should delete intermediate object file once its content + // is brought to memory. Return NULL is the compilation was not successful. + // const void *compile(size_t *length, std::string &errMsg); - void setCodeGenDebugOptions(const char *opts); private: void initializeLTOPasses(); |