# builder.tcl --
#
#	Class that allows for building new quadcode inside a
#	quadcode::transformer.
#
# Copyright (c) 2018 by Kevin B. Kenny
#
# See the file "license.terms" for information on usage and redistribution
# of this file, and for a DISCLAIMER OF ALL WARRANTIES.
#
# Some passes that modify quadcode do fairly extensive code rewriting, and
# it's convenient have procedures to track these and allow access at a level
# closer to an 'assembly language'. This class contains convenience methods
# to allow automatic tracking of variable uses and defs, named temporaries,
# and named basic blocks.
#
#------------------------------------------------------------------------------

# quadcode::builder --
#
#	Class with support methods for building quadcode.
#
oo::class create quadcode::builder {

    variable xfmr;		# quadcode::transformer object containing
    ;				# the quadcode of interest.

    variable b;			# Basic block number under construction

    variable bb;		# Content of the basic block under construction

    variable bbindex;		# Dictionary whose keys are the names of
    ;				# basic blocks and whose values are the
    ;				# basic block numbers.

    variable varindex;		# Dictionary whose keys are named variables
    ;				# and whose values are the SSA names of the
    ;				# variables.
}

# quadcode::builder constructor --
#
#	Makes a quadcode::builder to allow for assembling quadcode.
#
# Parameters:
#	xfmr - quadcode::transformer object containing the subprogram
#	b - Basic block number under construction
#	bb - Basic block content of the block under construction

oo::define quadcode::builder constructor {xfmr_ b_ bb_} {
    set xfmr $xfmr_
    set b $b_
    set bb $bb_
    set bbindex {}
    set varindex {}
}

# quadcode::builder maketemp --
#
#	Makes a temporary variable.
#
# Parameters:
#	name - Base name for the temporary.
#
# Results:
#	Returns the name of the constructed temporary.
#
# Side effects:
#	Stores the name as the most recent instance of the temporary.

oo::define quadcode::builder method maketemp {name} {
    set ssaname [$xfmr newVarInstance [list temp @$name]]
    dict set varindex $name $ssaname
    return $ssaname
}

# quadcode::builder method emit --
#
#	Emits an instruction into the basic block under construction.
#
# Parameters:
#	q - Quadcode instruction to emit
#
# Results:
#	None.
#
# Side effects:
#	Appends the instruction to the basic bnlock under construction.
#	If the instruction is a jump, adds the basic block predecessor
#	relationship. If the instruction is an assignment, updates the
#	ud-chain of the assigned variable. Updates the du-chains of all
#	variables used oin the instruction.

oo::define quadcode::builder method emit {q} {

    # Split the instruction
    lassign $q opcode res argl

    # Handle the result
    switch -exact -- [lindex $res 0] {
        "bb" {

	    # Instruction is a jump, link the basic block to the jump target
            $xfmr bblink $b [lindex $res 1]
        }
        "temp" - "var" {

	    # Instrtuction is an assignment, update the ud-chain.
            dict set udchain $res $b
        }
    }

    # Handle the arguments
    foreach arg [lrange $q 2 end] {
        switch -exact -- [lindex $arg 0] {
            "temp" - "var" {

		# Argument is an SSA value, update the du-chain.
		$xfmr addUse $arg $b
            }
        }
    }

    # Add the instruction to the block
    lappend bb $q

    return
}

# quadcode::builder method bb --
#
#	Returns the content of the basic block under construction.
#
# Results:
#	Returns the instructions.

oo::define quadcode::builder method bb {} {
    return $bb
}

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