Goose  Artifact [d7ab488717]

Artifact d7ab488717c869bc83f10c5dea9c2db23e5f08fe2fe015f8a06f5b4decf6dcc4:

• File bs/builtins/statements/while.cpp — part of check-in [b3aeaae2df] at 2020-01-11 18:28:15 on branch trunk —
  • Moved the cfg and lifetime management stuff into a CodeBuilder object owned by sema::Context. This is in preparation to allow alternative implementations of the builder, for instance to build classes.
  • Pass the context to intrinsic functions, which removes their dependency to the parser the need for the ugly "GetCurrentParser" static function.
  (user: achavasse size: 5776)

#include "builtins/builtins.h"
#include "parse/parse.h"
#include "precedence.h"
#include "builtins/helpers.h"

using namespace goose;
using namespace goose::ir;
using namespace goose::parse;

namespace goose::builtins
{
    void SetupWhileStmt( Env& e )
    {
        auto handleWhile = []( Parser& p, uint32_t locationId, uint32_t prec )
        {
            auto& dm = DiagnosticsManager::GetInstance();
            const auto& cb = p.context().codeBuilder();

            if( p.isInParenExpr() || !cb )
            {
                dm.emitSyntaxErrorMessage( locationId, "the while statement is not allowed here.", 0 );
                return false;
            }

            const auto& cfg = cb->cfg();
            auto pPrecBB = cfg->currentBB();

            if( !pPrecBB || pPrecBB->terminator() )
            {
                DiagnosticsManager::GetInstance().emitSyntaxErrorMessage(
                    locationId, "unreachable code.", 0 );
                cfg->poison();
            }

            // Create a scope for the entire while, so that any var declared
            // inside of the condition is alive and visible throughout the while.
            Scope s( p );

            auto np = p.makeNestedParser();
            if( !np.parseExpression( precedence::IfStmt ) )
            {
                dm.emitSyntaxErrorMessage( locationId, "expected an expression following the while statement.", 0 );
                return false;
            }

            auto condVal = np.popValue();
            if( !condVal )
            {
                dm.emitSyntaxErrorMessage( locationId, "expected an expression following the while statement.", 0 );
                return false;
            }

            const auto& context = p.context();
            auto converted = ConvertValueToType( context, *condVal, GetValueType< bool >() );
            if( holds_alternative< ValUnifyError >( converted ) )
            {
                switch( get< ValUnifyError >( converted ) )
                {
                    // If the condition is invalid, bail out and mark the current
                    // diagnostics context as bust to avoid spamming cascading errors.
                    case ValUnifyError::NoSolution:
                        dm.emitSyntaxErrorMessage( condVal->locationId(), "the while condition can't be converted to a bool." );
                        break;

                    case ValUnifyError::Ambiguous:
                        dm.emitSyntaxErrorMessage( condVal->locationId(), "ambiguous while condition bool conversion." );
                        break;
                }

                return false;
            }

            if( get< Value >( converted ).isPoison() )
                cb->poison();

            // The condition may have emitted additional basic blocks, so get the current block again.
            pPrecBB = cfg->currentBB();

            auto pHeaderBB = cfg->createBB();

            // Set the loop header's location to a span including the while keyword and the condition
            pHeaderBB->setLocationId( Location::CreateSpanningLocation( locationId, condVal->locationId() ) );

            CodeBuilder::BreakableScopeGuard bsg( cb );
            CodeBuilder::ContinuableScopeGuard csg( cb );

            auto pBodyBB = ParseSubStatement( p, precedence::IfStmt );
            if( !pBodyBB )
            {
                dm.emitSyntaxErrorMessage( p.resolver()->currentLocation(), "expected a statement after the while condition.", 0 );
                return false;
            }

            if( !pPrecBB )
                return true;

            // Retrieve the final block of the loop body, if any
            if( auto pBodySuccBB = cfg->currentBB(); pBodySuccBB && !pBodySuccBB->terminator() )
            {
                // Jump from the end of the body BB back to the loop header
                pBodySuccBB->setTerminator( llr::Branch( pHeaderBB ) );
            }

            // Jump unconditionally from the pred block to the loop header.
            pPrecBB->setTerminator( llr::Branch( pHeaderBB ) );

            auto pSuccBB = cfg->createBB();

            auto breakLevel = cb->breakableScopeLevels();
            auto continueLevel = cb->continuableScopeLevels();

            // Go through all basic blocks, find all break and continue terminators
            // for our scope level and replace them with branches respectively to
            // the successor BB or to the loop header BB.
            cfg->forEachBB( [&]( auto&& bb )
            {
                const auto& t = bb->terminator();
                if( !t )
                    return;

                if( const auto* pBreak = get_if< llr::Break >( &t->content() ) )
                {
                    if( pBreak->level() == breakLevel )
                        bb->setTerminator( llr::Branch( pSuccBB ) );
                    return;
                }

                if( const auto* pCont = get_if< llr::Continue >( &t->content() ) )
                {
                    if( pCont->level() == continueLevel )
                        bb->setTerminator( llr::Branch( pHeaderBB ) );
                    return;
                }
            } );

            // Emit the conditional branch that will either run an iteration of the loop or exit to the succ bb.
            pHeaderBB->setTerminator( llr::CondBranch(
                get< Value >( converted ),
                pBodyBB, pSuccBB ) );

            cfg->setCurrentBB( pSuccBB );
            return true;
        };

        Rule r( handleWhile );
        auto ruleVal = ToValue( move( r ) );
        auto ruleTerm = ValueToIRExpr( ruleVal );
        e.storeValue( AppendToVectorTerm( RootIdentity(), TSID( while ) ), ANYTERM( _ ), ruleTerm );
    }
}