forked from github/verilator
113 lines
3.2 KiB
C++
113 lines
3.2 KiB
C++
// -*- mode: C++; c-file-style: "cc-mode" -*-
|
||
//*************************************************************************
|
||
// DESCRIPTION: Verilator: Branch prediction
|
||
//
|
||
// Code available from: http://www.veripool.org/verilator
|
||
//
|
||
// AUTHORS: Wilson Snyder with Paul Wasson, Duane Gabli
|
||
//
|
||
//*************************************************************************
|
||
//
|
||
// Copyright 2003-2012 by Wilson Snyder. This program is free software; you can
|
||
// redistribute it and/or modify it under the terms of either the GNU
|
||
// Lesser General Public License Version 3 or the Perl Artistic License
|
||
// Version 2.0.
|
||
//
|
||
// Verilator is distributed in the hope that it will be useful,
|
||
// but WITHOUT ANY WARRANTY; without even the implied warranty of
|
||
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
||
// GNU General Public License for more details.
|
||
//
|
||
//*************************************************************************
|
||
// BRANCH TRANSFORMATIONS:
|
||
// At each IF/(IF else).
|
||
// Count underneath $display/$stop statements.
|
||
// If more on if than else, this branch is unlikely, or vice-versa.
|
||
//
|
||
//*************************************************************************
|
||
|
||
#include "config_build.h"
|
||
#include "verilatedos.h"
|
||
#include <cstdio>
|
||
#include <cstdarg>
|
||
#include <unistd.h>
|
||
#include <map>
|
||
|
||
#include "V3Global.h"
|
||
#include "V3Branch.h"
|
||
#include "V3Ast.h"
|
||
|
||
//######################################################################
|
||
// Branch state, as a visitor of each AstNode
|
||
|
||
class BranchVisitor : public AstNVisitor {
|
||
private:
|
||
// STATE
|
||
int m_likely; // Excuses for branch likely taken
|
||
int m_unlikely; // Excuses for branch likely not taken
|
||
|
||
// METHODS
|
||
static int debug() {
|
||
static int level = -1;
|
||
if (VL_UNLIKELY(level < 0)) level = v3Global.opt.debugSrcLevel(__FILE__);
|
||
return level;
|
||
}
|
||
|
||
void reset() {
|
||
m_likely = false;
|
||
m_unlikely = false;
|
||
}
|
||
|
||
// VISITORS
|
||
virtual void visit(AstNodeIf* nodep, AstNUser*) {
|
||
UINFO(4," IF: "<<nodep<<endl);
|
||
int lastLikely = m_likely;
|
||
int lastUnlikely = m_unlikely;
|
||
{
|
||
// Do if
|
||
reset();
|
||
nodep->ifsp()->iterateAndNext(*this);
|
||
int ifLikely = m_likely;
|
||
int ifUnlikely = m_unlikely;
|
||
// Do else
|
||
reset();
|
||
nodep->elsesp()->iterateAndNext(*this);
|
||
int elseLikely = m_likely;
|
||
int elseUnlikely = m_unlikely;
|
||
// Compute
|
||
int likeness = ifLikely - ifUnlikely - (elseLikely - elseUnlikely);
|
||
if (likeness>0) {
|
||
nodep->branchPred(AstBranchPred::BP_LIKELY);
|
||
} else if (likeness<0) {
|
||
nodep->branchPred(AstBranchPred::BP_UNLIKELY);
|
||
} // else leave unknown
|
||
}
|
||
m_likely = lastLikely;
|
||
m_unlikely = lastUnlikely;
|
||
}
|
||
virtual void visit(AstNode* nodep, AstNUser*) {
|
||
// Default: Just iterate
|
||
if (nodep->isUnlikely()) {
|
||
UINFO(4," UNLIKELY: "<<nodep<<endl);
|
||
m_unlikely++;
|
||
}
|
||
nodep->iterateChildren(*this);
|
||
}
|
||
|
||
public:
|
||
// CONSTUCTORS
|
||
BranchVisitor(AstNetlist* rootp) {
|
||
reset();
|
||
rootp->iterateChildren(*this);
|
||
}
|
||
virtual ~BranchVisitor() {}
|
||
};
|
||
|
||
//######################################################################
|
||
// Branch class functions
|
||
|
||
void V3Branch::branchAll(AstNetlist* rootp) {
|
||
UINFO(2,__FUNCTION__<<": "<<endl);
|
||
BranchVisitor visitor (rootp);
|
||
}
|