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62cd3418ca142a888432c60e00457dc7a011f04c
ispc/ast.cpp
Matt Pharr 117f48a331 Don't include foreach stmts in cost estimates from EstimateCost(). 
Because they reestablish an 'all on' mask inside their body, it doesn't
make sense to include their cost when evaluating whether it's worth
re-establishing an 'all on' mask dynamically.  (This does mean that
EstimateCost()'s return value isn't the most obvious thing, but currently
in all the cases where we need it, this is the more appropriate value to
return.)
2012-03-25 10:32:44 -07:00

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/*
Copyright (c) 2011-2012, Intel Corporation
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
* Neither the name of Intel Corporation nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/** @file ast.cpp
@brief General functionality related to abstract syntax trees and
traversal of them.
*/
#include "ast.h"
#include "expr.h"
#include "func.h"
#include "stmt.h"
#include "sym.h"
#include "util.h"
///////////////////////////////////////////////////////////////////////////
// ASTNode
ASTNode::~ASTNode() {
}
///////////////////////////////////////////////////////////////////////////
// AST
void
AST::AddFunction(Symbol *sym, const std::vector<Symbol *> &args, Stmt *code) {
if (sym == NULL)
return;
functions.push_back(new Function(sym, args, code));
}
void
AST::GenerateIR() {
for (unsigned int i = 0; i < functions.size(); ++i)
functions[i]->GenerateIR();
}
///////////////////////////////////////////////////////////////////////////
ASTNode *
WalkAST(ASTNode *node, ASTPreCallBackFunc preFunc, ASTPostCallBackFunc postFunc,
void *data) {
if (node == NULL)
return node;
// Call the callback function
if (preFunc != NULL) {
if (preFunc(node, data) == false)
// The function asked us to not continue recursively, so stop.
return node;
}
////////////////////////////////////////////////////////////////////////////
// Handle Statements
if (dynamic_cast<Stmt *>(node) != NULL) {
ExprStmt *es;
DeclStmt *ds;
IfStmt *is;
DoStmt *dos;
ForStmt *fs;
ForeachStmt *fes;
CaseStmt *cs;
DefaultStmt *defs;
SwitchStmt *ss;
ReturnStmt *rs;
LabeledStmt *ls;
StmtList *sl;
PrintStmt *ps;
AssertStmt *as;
DeleteStmt *dels;
if ((es = dynamic_cast<ExprStmt *>(node)) != NULL)
es->expr = (Expr *)WalkAST(es->expr, preFunc, postFunc, data);
else if ((ds = dynamic_cast<DeclStmt *>(node)) != NULL) {
for (unsigned int i = 0; i < ds->vars.size(); ++i)
ds->vars[i].init = (Expr *)WalkAST(ds->vars[i].init, preFunc,
postFunc, data);
}
else if ((is = dynamic_cast<IfStmt *>(node)) != NULL) {
is->test = (Expr *)WalkAST(is->test, preFunc, postFunc, data);
is->trueStmts = (Stmt *)WalkAST(is->trueStmts, preFunc,
postFunc, data);
is->falseStmts = (Stmt *)WalkAST(is->falseStmts, preFunc,
postFunc, data);
}
else if ((dos = dynamic_cast<DoStmt *>(node)) != NULL) {
dos->testExpr = (Expr *)WalkAST(dos->testExpr, preFunc,
postFunc, data);
dos->bodyStmts = (Stmt *)WalkAST(dos->bodyStmts, preFunc,
postFunc, data);
}
else if ((fs = dynamic_cast<ForStmt *>(node)) != NULL) {
fs->init = (Stmt *)WalkAST(fs->init, preFunc, postFunc, data);
fs->test = (Expr *)WalkAST(fs->test, preFunc, postFunc, data);
fs->step = (Stmt *)WalkAST(fs->step, preFunc, postFunc, data);
fs->stmts = (Stmt *)WalkAST(fs->stmts, preFunc, postFunc, data);
}
else if ((fes = dynamic_cast<ForeachStmt *>(node)) != NULL) {
for (unsigned int i = 0; i < fes->startExprs.size(); ++i)
fes->startExprs[i] = (Expr *)WalkAST(fes->startExprs[i], preFunc,
postFunc, data);
for (unsigned int i = 0; i < fes->endExprs.size(); ++i)
fes->endExprs[i] = (Expr *)WalkAST(fes->endExprs[i], preFunc,
postFunc, data);
fes->stmts = (Stmt *)WalkAST(fes->stmts, preFunc, postFunc, data);
}
else if ((cs = dynamic_cast<CaseStmt *>(node)) != NULL)
cs->stmts = (Stmt *)WalkAST(cs->stmts, preFunc, postFunc, data);
else if ((defs = dynamic_cast<DefaultStmt *>(node)) != NULL)
defs->stmts = (Stmt *)WalkAST(defs->stmts, preFunc, postFunc, data);
else if ((ss = dynamic_cast<SwitchStmt *>(node)) != NULL) {
ss->expr = (Expr *)WalkAST(ss->expr, preFunc, postFunc, data);
ss->stmts = (Stmt *)WalkAST(ss->stmts, preFunc, postFunc, data);
}
else if (dynamic_cast<BreakStmt *>(node) != NULL ||
dynamic_cast<ContinueStmt *>(node) != NULL ||
dynamic_cast<GotoStmt *>(node) != NULL) {
// nothing
}
else if ((ls = dynamic_cast<LabeledStmt *>(node)) != NULL)
ls->stmt = (Stmt *)WalkAST(ls->stmt, preFunc, postFunc, data);
else if ((rs = dynamic_cast<ReturnStmt *>(node)) != NULL)
rs->val = (Expr *)WalkAST(rs->val, preFunc, postFunc, data);
else if ((sl = dynamic_cast<StmtList *>(node)) != NULL) {
std::vector<Stmt *> &sls = sl->stmts;
for (unsigned int i = 0; i < sls.size(); ++i)
sls[i] = (Stmt *)WalkAST(sls[i], preFunc, postFunc, data);
}
else if ((ps = dynamic_cast<PrintStmt *>(node)) != NULL)
ps->values = (Expr *)WalkAST(ps->values, preFunc, postFunc, data);
else if ((as = dynamic_cast<AssertStmt *>(node)) != NULL)
as->expr = (Expr *)WalkAST(as->expr, preFunc, postFunc, data);
else if ((dels = dynamic_cast<DeleteStmt *>(node)) != NULL)
dels->expr = (Expr *)WalkAST(dels->expr, preFunc, postFunc, data);
else
FATAL("Unhandled statement type in WalkAST()");
}
else {
///////////////////////////////////////////////////////////////////////////
// Handle expressions
Assert(dynamic_cast<Expr *>(node) != NULL);
UnaryExpr *ue;
BinaryExpr *be;
AssignExpr *ae;
SelectExpr *se;
ExprList *el;
FunctionCallExpr *fce;
IndexExpr *ie;
MemberExpr *me;
TypeCastExpr *tce;
ReferenceExpr *re;
PtrDerefExpr *ptrderef;
RefDerefExpr *refderef;
SizeOfExpr *soe;
AddressOfExpr *aoe;
NewExpr *newe;
if ((ue = dynamic_cast<UnaryExpr *>(node)) != NULL)
ue->expr = (Expr *)WalkAST(ue->expr, preFunc, postFunc, data);
else if ((be = dynamic_cast<BinaryExpr *>(node)) != NULL) {
be->arg0 = (Expr *)WalkAST(be->arg0, preFunc, postFunc, data);
be->arg1 = (Expr *)WalkAST(be->arg1, preFunc, postFunc, data);
}
else if ((ae = dynamic_cast<AssignExpr *>(node)) != NULL) {
ae->lvalue = (Expr *)WalkAST(ae->lvalue, preFunc, postFunc, data);
ae->rvalue = (Expr *)WalkAST(ae->rvalue, preFunc, postFunc, data);
}
else if ((se = dynamic_cast<SelectExpr *>(node)) != NULL) {
se->test = (Expr *)WalkAST(se->test, preFunc, postFunc, data);
se->expr1 = (Expr *)WalkAST(se->expr1, preFunc, postFunc, data);
se->expr2 = (Expr *)WalkAST(se->expr2, preFunc, postFunc, data);
}
else if ((el = dynamic_cast<ExprList *>(node)) != NULL) {
for (unsigned int i = 0; i < el->exprs.size(); ++i)
el->exprs[i] = (Expr *)WalkAST(el->exprs[i], preFunc,
postFunc, data);
}
else if ((fce = dynamic_cast<FunctionCallExpr *>(node)) != NULL) {
fce->func = (Expr *)WalkAST(fce->func, preFunc, postFunc, data);
fce->args = (ExprList *)WalkAST(fce->args, preFunc, postFunc, data);
fce->launchCountExpr = (Expr *)WalkAST(fce->launchCountExpr, preFunc,
postFunc, data);
}
else if ((ie = dynamic_cast<IndexExpr *>(node)) != NULL) {
ie->baseExpr = (Expr *)WalkAST(ie->baseExpr, preFunc, postFunc, data);
ie->index = (Expr *)WalkAST(ie->index, preFunc, postFunc, data);
}
else if ((me = dynamic_cast<MemberExpr *>(node)) != NULL)
me->expr = (Expr *)WalkAST(me->expr, preFunc, postFunc, data);
else if ((tce = dynamic_cast<TypeCastExpr *>(node)) != NULL)
tce->expr = (Expr *)WalkAST(tce->expr, preFunc, postFunc, data);
else if ((re = dynamic_cast<ReferenceExpr *>(node)) != NULL)
re->expr = (Expr *)WalkAST(re->expr, preFunc, postFunc, data);
else if ((ptrderef = dynamic_cast<PtrDerefExpr *>(node)) != NULL)
ptrderef->expr = (Expr *)WalkAST(ptrderef->expr, preFunc, postFunc,
data);
else if ((refderef = dynamic_cast<RefDerefExpr *>(node)) != NULL)
refderef->expr = (Expr *)WalkAST(refderef->expr, preFunc, postFunc,
data);
else if ((soe = dynamic_cast<SizeOfExpr *>(node)) != NULL)
soe->expr = (Expr *)WalkAST(soe->expr, preFunc, postFunc, data);
else if ((aoe = dynamic_cast<AddressOfExpr *>(node)) != NULL)
aoe->expr = (Expr *)WalkAST(aoe->expr, preFunc, postFunc, data);
else if ((newe = dynamic_cast<NewExpr *>(node)) != NULL) {
newe->countExpr = (Expr *)WalkAST(newe->countExpr, preFunc,
postFunc, data);
newe->initExpr = (Expr *)WalkAST(newe->initExpr, preFunc,
postFunc, data);
}
else if (dynamic_cast<SymbolExpr *>(node) != NULL ||
dynamic_cast<ConstExpr *>(node) != NULL ||
dynamic_cast<FunctionSymbolExpr *>(node) != NULL ||
dynamic_cast<SyncExpr *>(node) != NULL ||
dynamic_cast<NullPointerExpr *>(node) != NULL) {
// nothing to do
}
else
FATAL("Unhandled expression type in WalkAST().");
}
// Call the callback function
if (postFunc != NULL)
return postFunc(node, data);
else
return node;
}
static ASTNode *
lOptimizeNode(ASTNode *node, void *) {
return node->Optimize();
}
ASTNode *
Optimize(ASTNode *root) {
return WalkAST(root, NULL, lOptimizeNode, NULL);
}
Expr *
Optimize(Expr *expr) {
return (Expr *)Optimize((ASTNode *)expr);
}
Stmt *
Optimize(Stmt *stmt) {
return (Stmt *)Optimize((ASTNode *)stmt);
}
static ASTNode *
lTypeCheckNode(ASTNode *node, void *) {
return node->TypeCheck();
}
ASTNode *
TypeCheck(ASTNode *root) {
return WalkAST(root, NULL, lTypeCheckNode, NULL);
}
Expr *
TypeCheck(Expr *expr) {
return (Expr *)TypeCheck((ASTNode *)expr);
}
Stmt *
TypeCheck(Stmt *stmt) {
return (Stmt *)TypeCheck((ASTNode *)stmt);
}
struct CostData {
CostData() { cost = foreachDepth = 0; }
int cost;
int foreachDepth;
};
static bool
lCostCallbackPre(ASTNode *node, void *d) {
CostData *data = (CostData *)d;
if (dynamic_cast<ForeachStmt *>(node) != NULL)
++data->foreachDepth;
if (data->foreachDepth == 0)
data->cost += node->EstimateCost();
return true;
}
static ASTNode *
lCostCallbackPost(ASTNode *node, void *d) {
CostData *data = (CostData *)d;
if (dynamic_cast<ForeachStmt *>(node) != NULL)
--data->foreachDepth;
return node;
}
int
EstimateCost(ASTNode *root) {
CostData data;
WalkAST(root, lCostCallbackPre, lCostCallbackPost, &data);
return data.cost;
}
/** Given an AST node, check to see if it's safe if we happen to run the
code for that node with the execution mask all off.
*/
static bool
lCheckAllOffSafety(ASTNode *node, void *data) {
bool *okPtr = (bool *)data;
FunctionCallExpr *fce;
if ((fce = dynamic_cast<FunctionCallExpr *>(node)) != NULL) {
if (fce->func == NULL)
return false;
const Type *type = fce->func->GetType();
const PointerType *pt = dynamic_cast<const PointerType *>(type);
if (pt != NULL)
type = pt->GetBaseType();
const FunctionType *ftype = dynamic_cast<const FunctionType *>(type);
Assert(ftype != NULL);
if (ftype->isSafe == false) {
*okPtr = false;
return false;
}
}
if (dynamic_cast<AssertStmt *>(node) != NULL) {
// While it's fine to run the assert for varying tests, it's not
// desirable to check an assert on a uniform variable if all of the
// lanes are off.
*okPtr = false;
return false;
}
if (dynamic_cast<NewExpr *>(node) != NULL ||
dynamic_cast<DeleteStmt *>(node) != NULL) {
// We definitely don't want to run the uniform variants of these if
// the mask is all off. It's also worth skipping the overhead of
// executing the varying versions of them in the all-off mask case.
*okPtr = false;
return false;
}
if (dynamic_cast<ForeachStmt *>(node) != NULL) {
// foreach() statements also shouldn't be run with an all-off mask.
// Since they re-establish an 'all on' mask, this would be pretty
// unintuitive. (More generally, it's possibly a little strange to
// allow foreach() in the presence of any non-uniform control
// flow...)
*okPtr = false;
return false;
}
if (g->target.allOffMaskIsSafe == true)
// Don't worry about memory accesses if we have a target that can
// safely run them with the mask all off
return true;
IndexExpr *ie;
if ((ie = dynamic_cast<IndexExpr *>(node)) != NULL && ie->baseExpr != NULL) {
const Type *type = ie->baseExpr->GetType();
if (type == NULL)
return true;
if (dynamic_cast<const ReferenceType *>(type) != NULL)
type = type->GetReferenceTarget();
ConstExpr *ce = dynamic_cast<ConstExpr *>(ie->index);
if (ce == NULL) {
// indexing with a variable... -> not safe
*okPtr = false;
return false;
}
const PointerType *pointerType =
dynamic_cast<const PointerType *>(type);
if (pointerType != NULL) {
// pointer[index] -> can't be sure -> not safe
*okPtr = false;
return false;
}
const SequentialType *seqType =
dynamic_cast<const SequentialType *>(type);
Assert(seqType != NULL);
int nElements = seqType->GetElementCount();
if (nElements == 0) {
// Unsized array, so we can't be sure -> not safe
*okPtr = false;
return false;
}
int32_t indices[ISPC_MAX_NVEC];
int count = ce->AsInt32(indices);
for (int i = 0; i < count; ++i) {
if (indices[i] < 0 || indices[i] >= nElements) {
// Index is out of bounds -> not safe
*okPtr = false;
return false;
}
}
// All indices are in-bounds
return true;
}
MemberExpr *me;
if ((me = dynamic_cast<MemberExpr *>(node)) != NULL &&
me->dereferenceExpr) {
*okPtr = false;
return false;
}
if (dynamic_cast<PtrDerefExpr *>(node) != NULL) {
*okPtr = false;
return false;
}
return true;
}
bool
SafeToRunWithMaskAllOff(ASTNode *root) {
bool safe = true;
WalkAST(root, lCheckAllOffSafety, NULL, &safe);
return safe;
}
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