ast.cpp

/*
  Copyright (c) 2011-2012, Intel Corporation
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  met:

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      notice, this list of conditions and the following disclaimer.

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      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.

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      contributors may be used to endorse or promote products derived from
      this software without specific prior written permission.


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   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
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*/

/** @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, Stmt *code) {
    if (sym == NULL)
        return;
    functions.push_back(new Function(sym, 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;
        ForeachActiveStmt *fas;
        ForeachUniqueStmt *fus;
        CaseStmt *cs;
        DefaultStmt *defs;
        SwitchStmt *ss;
        ReturnStmt *rs;
        LabeledStmt *ls;
        StmtList *sl;
        PrintStmt *ps;
        AssertStmt *as;
        DeleteStmt *dels;
        UnmaskedStmt *ums;

        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 ((fas = dynamic_cast<ForeachActiveStmt *>(node)) != NULL) {
            fas->stmts = (Stmt *)WalkAST(fas->stmts, preFunc, postFunc, data);
        }
        else if ((fus = dynamic_cast<ForeachUniqueStmt *>(node)) != NULL) {
            fus->expr = (Expr *)WalkAST(fus->expr, preFunc, postFunc, data);
            fus->stmts = (Stmt *)WalkAST(fus->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->expr = (Expr *)WalkAST(rs->expr, 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 if ((ums = dynamic_cast<UnmaskedStmt *>(node)) != NULL)
            ums->stmts = (Stmt *)WalkAST(ums->stmts, 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 = CastType<PointerType>(type);
        if (pt != NULL)
            type = pt->GetBaseType();
        const FunctionType *ftype = CastType<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 ||
        dynamic_cast<ForeachActiveStmt *>(node) != NULL ||
        dynamic_cast<ForeachUniqueStmt *>(node) != NULL ||
        dynamic_cast<UnmaskedStmt *>(node) != NULL) {
        // The various foreach statements also shouldn't be run with an
        // all-off mask.  Since they can 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...)
        //
        // Similarly, the implementation of foreach_unique assumes as a
        // precondition that the mask won't be all off going into it, so
        // we'll enforce that here...
        *okPtr = false;
        return false;
    }

    IndexExpr *ie;
    if ((ie = dynamic_cast<IndexExpr *>(node)) != NULL && ie->baseExpr != NULL) {
        const Type *type = ie->baseExpr->GetType();
        if (type == NULL)
            return true;
        if (CastType<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 = CastType<PointerType>(type);
        if (pointerType != NULL) {
            // pointer[index] -> can't be sure -> not safe
            *okPtr = false;
            return false;
        }

        const SequentialType *seqType = CastType<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;
}