ldc/gen/pragma.h
Johan Engelen e0d9c58443 [PGO] Add PGO to LDC. Supported for LLVM >= 3.7
Add the commandline options -fprofile-instr-generate[=filename] and -profile-instr-use=filename
-fprofile-instr-generate
-- Add instrumentation on branches, switches, and function entry; uses LLVM's InstrProf pass.
-- Link to profile runtime that writes instrumentation counters to a file.
-fprofile-instr-use
-- Read profile data from a file and apply branch weights to branches and switches, and annotate functions with entrycount in LLVM IR.
-- Functions with low or high entrycount are marked with 'cold' or 'inlinehint'.

The only statement type without PGO yet is "try-finally".

A new pragma, `pragma(LDC_profile_instr, [ true | false ])`, is added to selectively disable/enable instrumentation of functions (granularity = whole functions).

The runtime library ldc-profile-rt is a copy of LLVM compiler-rt lib/profile. It has to be exactly in-sync with the LLVM version, and thus we need a copy for each PGO-supported LLVM (>=3.7).
import ldc.profile for a D interface to ldc-profile-rt (for example to reset execution counts after a program startup phase).

The instrumentation data is mainly passed on to LLVM: function-entry counts and branch counts/probabilities. LDC marks functions as hot when "execution count is 30% of the maximum function execution count", and marks functions as cold if their count is 1% of maximum function execution count.

The source of LLVM's llvm-profdata tool is hereby included in LDCs repository (different source for each LLVM version), and the binary is included in the install bin folder.
The executable is named "ldc-profdata" to avoid clashing with llvm-profdata on the same machine. This is needed because profdata executable has to be in-sync with the LLVM version used to build LDC.

Maintenance burden: for trunk LLVM, we have to keep ldc-profile-rt and llvm-profdata in sync. There is no diff with upstream; but because of active development there are the occasional API changes.
2016-06-20 17:28:22 +02:00

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//===-- gen/pragma.h - LDC-specific pragma handling -------------*- C++ -*-===//
//
// LDC the LLVM D compiler
//
// This file is distributed under the BSD-style LDC license. See the LICENSE
// file for details.
//
//===----------------------------------------------------------------------===//
//
// Code for handling the LDC-specific pragmas.
//
//===----------------------------------------------------------------------===//
#ifndef LDC_GEN_PRAGMA_H
#define LDC_GEN_PRAGMA_H
#include <string>
class PragmaDeclaration;
class FuncDeclaration;
class Dsymbol;
struct Scope;
class Expression;
// Remember to keep this enum in-sync with dpragma.d
enum LDCPragma {
LLVMnone = 0, // Not an LDC pragma.
LLVMignore, // Pragma has already been processed in DtoGetPragma, ignore.
LLVMintrinsic,
LLVMglobal_crt_ctor,
LLVMglobal_crt_dtor,
LLVMno_typeinfo,
LLVMalloca,
LLVMva_start,
LLVMva_copy,
LLVMva_end,
LLVMva_arg,
LLVMinline_asm,
LLVMinline_ir,
LLVMfence,
LLVMatomic_store,
LLVMatomic_load,
LLVMatomic_cmp_xchg,
LLVMatomic_rmw,
LLVMbitop_bt,
LLVMbitop_btc,
LLVMbitop_btr,
LLVMbitop_bts,
LLVMbitop_vld,
LLVMbitop_vst,
LLVMextern_weak,
LLVMprofile_instr
};
LDCPragma DtoGetPragma(Scope *sc, PragmaDeclaration *decl, const char *&arg1str);
void DtoCheckPragma(PragmaDeclaration *decl, Dsymbol *sym, LDCPragma llvm_internal,
const char * const arg1str);
bool DtoCheckProfileInstrPragma(Expression *arg, bool &value);
bool DtoIsIntrinsic(FuncDeclaration *fd);
bool DtoIsVaIntrinsic(FuncDeclaration *fd);
#endif // LDC_GEN_PRAGMA_H