ast.cpp

/*
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      this software without specific prior written permission.


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   IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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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 (llvm::dyn_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 = llvm::dyn_cast<ExprStmt>(node)) != NULL)
            es->expr = (Expr *)WalkAST(es->expr, preFunc, postFunc, data);
        else if ((ds = llvm::dyn_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 = llvm::dyn_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 = llvm::dyn_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 = llvm::dyn_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 = llvm::dyn_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 = llvm::dyn_cast<ForeachActiveStmt>(node)) != NULL) {
            fas->stmts = (Stmt *)WalkAST(fas->stmts, preFunc, postFunc, data);
        }
        else if ((fus = llvm::dyn_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 = llvm::dyn_cast<CaseStmt>(node)) != NULL)
            cs->stmts = (Stmt *)WalkAST(cs->stmts, preFunc, postFunc, data);
        else if ((defs = llvm::dyn_cast<DefaultStmt>(node)) != NULL)
            defs->stmts = (Stmt *)WalkAST(defs->stmts, preFunc, postFunc, data);
        else if ((ss = llvm::dyn_cast<SwitchStmt>(node)) != NULL) {
            ss->expr = (Expr *)WalkAST(ss->expr, preFunc, postFunc, data);
            ss->stmts = (Stmt *)WalkAST(ss->stmts, preFunc, postFunc, data);
        }
        else if (llvm::dyn_cast<BreakStmt>(node) != NULL ||
                 llvm::dyn_cast<ContinueStmt>(node) != NULL ||
                 llvm::dyn_cast<GotoStmt>(node) != NULL) {
            // nothing
        }
        else if ((ls = llvm::dyn_cast<LabeledStmt>(node)) != NULL)
            ls->stmt = (Stmt *)WalkAST(ls->stmt, preFunc, postFunc, data);
        else if ((rs = llvm::dyn_cast<ReturnStmt>(node)) != NULL)
            rs->expr = (Expr *)WalkAST(rs->expr, preFunc, postFunc, data);
        else if ((sl = llvm::dyn_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 = llvm::dyn_cast<PrintStmt>(node)) != NULL)
            ps->values = (Expr *)WalkAST(ps->values, preFunc, postFunc, data);
        else if ((as = llvm::dyn_cast<AssertStmt>(node)) != NULL)
            as->expr = (Expr *)WalkAST(as->expr, preFunc, postFunc, data);
        else if ((dels = llvm::dyn_cast<DeleteStmt>(node)) != NULL)
            dels->expr = (Expr *)WalkAST(dels->expr, preFunc, postFunc, data);
        else if ((ums = llvm::dyn_cast<UnmaskedStmt>(node)) != NULL)
            ums->stmts = (Stmt *)WalkAST(ums->stmts, preFunc, postFunc, data);
        else
            FATAL("Unhandled statement type in WalkAST()");
    }
    else {
        ///////////////////////////////////////////////////////////////////////////
        // Handle expressions
        Assert(llvm::dyn_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 = llvm::dyn_cast<UnaryExpr>(node)) != NULL)
            ue->expr = (Expr *)WalkAST(ue->expr, preFunc, postFunc, data);
        else if ((be = llvm::dyn_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 = llvm::dyn_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 = llvm::dyn_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 = llvm::dyn_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 = llvm::dyn_cast<FunctionCallExpr>(node)) != NULL) {
            fce->func = (Expr *)WalkAST(fce->func, preFunc, postFunc, data);
            fce->args = (ExprList *)WalkAST(fce->args, preFunc, postFunc, data);
            for (int k = 0; k < 3; k++)
              fce->launchCountExpr[0] = (Expr *)WalkAST(fce->launchCountExpr[0], preFunc,
                                                   postFunc, data);
        }
        else if ((ie = llvm::dyn_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 = llvm::dyn_cast<MemberExpr>(node)) != NULL)
            me->expr = (Expr *)WalkAST(me->expr, preFunc, postFunc, data);
        else if ((tce = llvm::dyn_cast<TypeCastExpr>(node)) != NULL)
            tce->expr = (Expr *)WalkAST(tce->expr, preFunc, postFunc, data);
        else if ((re = llvm::dyn_cast<ReferenceExpr>(node)) != NULL)
            re->expr = (Expr *)WalkAST(re->expr, preFunc, postFunc, data);
        else if ((ptrderef = llvm::dyn_cast<PtrDerefExpr>(node)) != NULL)
            ptrderef->expr = (Expr *)WalkAST(ptrderef->expr, preFunc, postFunc,
                                             data);
        else if ((refderef = llvm::dyn_cast<RefDerefExpr>(node)) != NULL)
            refderef->expr = (Expr *)WalkAST(refderef->expr, preFunc, postFunc,
                                             data);
        else if ((soe = llvm::dyn_cast<SizeOfExpr>(node)) != NULL)
            soe->expr = (Expr *)WalkAST(soe->expr, preFunc, postFunc, data);
        else if ((aoe = llvm::dyn_cast<AddressOfExpr>(node)) != NULL)
            aoe->expr = (Expr *)WalkAST(aoe->expr, preFunc, postFunc, data);
        else if ((newe = llvm::dyn_cast<NewExpr>(node)) != NULL) {
            newe->countExpr = (Expr *)WalkAST(newe->countExpr, preFunc,
                                              postFunc, data);
            newe->initExpr = (Expr *)WalkAST(newe->initExpr, preFunc,
                                             postFunc, data);
        }
        else if (llvm::dyn_cast<SymbolExpr>(node) != NULL ||
                 llvm::dyn_cast<ConstExpr>(node) != NULL ||
                 llvm::dyn_cast<FunctionSymbolExpr>(node) != NULL ||
                 llvm::dyn_cast<SyncExpr>(node) != NULL ||
                 llvm::dyn_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 (llvm::dyn_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 (llvm::dyn_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 = llvm::dyn_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 (llvm::dyn_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 (llvm::dyn_cast<PrintStmt>(node) != NULL) {
        *okPtr = false;
        return false;
    }

    if (llvm::dyn_cast<NewExpr>(node) != NULL ||
        llvm::dyn_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 (llvm::dyn_cast<ForeachStmt>(node) != NULL ||
        llvm::dyn_cast<ForeachActiveStmt>(node) != NULL ||
        llvm::dyn_cast<ForeachUniqueStmt>(node) != NULL ||
        llvm::dyn_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;
    }

    if (llvm::dyn_cast<BinaryExpr>(node) != NULL) {
        BinaryExpr* binaryExpr = llvm::dyn_cast<BinaryExpr>(node);
        if (binaryExpr->op == BinaryExpr::Mod || binaryExpr->op == BinaryExpr::Div) {
            *okPtr = false;
            return false;
        }
    }
    IndexExpr *ie;
    if ((ie = llvm::dyn_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 = llvm::dyn_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->GetValues(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 = llvm::dyn_cast<MemberExpr>(node)) != NULL &&
        me->dereferenceExpr) {
        *okPtr = false;
        return false;
    }

    if (llvm::dyn_cast<PtrDerefExpr>(node) != NULL) {
        *okPtr = false;
        return false;
    }

    /*
      Don't allow turning if/else to straight-line-code if we 
      assign to a uniform.
    */
    AssignExpr *ae;
    if ((ae = llvm::dyn_cast<AssignExpr>(node)) != NULL) {
      if (ae->GetType()) {
        if (ae->GetType()->IsUniformType()) {
          *okPtr = false;
          return false;
        }
      }
    }

    return true;
}


bool
SafeToRunWithMaskAllOff(ASTNode *root) {
    bool safe = true;
    WalkAST(root, lCheckAllOffSafety, NULL, &safe);
    return safe;
}