Revising the architecture to better match Dybvig's P523 compiler
----------------------------------------------------------------

* to do: figure out where to introduce the Tail context. It seems to
  happen in Dybvig's A10, but that assignment doesn't say anything
  about it.

* to do: insert type checking


R1:

    exp ::= x | n | (op exp*) | (let ([x exp]) exp)
    R1 ::= (program exp)

uniquify
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V

    exp ::= x | n | (op exp*) | (let ([x exp]) exp)
    R1 ::= (program () exp)


remove-complex-opera*
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V

    arg ::= x | n
    exp ::= arg | (op arg*) | (let ([x exp]) exp)
    R1' ::= (program () exp)


create-CFG (the graph is empty for this assignment)
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V

    arg ::= x | n
    exp ::= arg | (op arg*)
    stmt ::= (assign x exp)
	tail ::= (return exp) | (stmt . tail)
    C0 ::= (program () tail)

uncover-locals
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V

    arg ::= x | n
    exp ::= arg | (op arg*)
    stmt ::= (assign x exp)
	tail ::= (return exp) | (stmt . tail)
    C0 ::= (program ((locals . x*)) tail)
    
select-instructions
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V

    imm ::= (var x) | (deref r n) | (int n)
    instr ::= (addq imm imm) | ...
    x86-CFG ::= (program ((locals . x*)) instr ...)

assign-homes
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V

    imm ::= (reg r) | (deref r n) | (int n)
    instr ::= (addq imm imm) | ...
    x86 ::= (program ((stack-space . n)  instr ...)
    
patch-instructions
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V

    same grammar as above

print-x86
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V



--------------------------------------------------------------------------------

R2:

    exp ::= x | n | #t | #f | (op exp*) | (let ([x exp]) exp) | (if exp exp exp)
    R2 ::= (program exp)

type-check
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V

    exp ::= x | n | #t | #f | (op exp*) | (let ([x exp]) exp) | (if exp exp exp)
    R2 ::= (program ((type . type)) exp)

remove-complex-opera*
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V

    arg ::= x | n | #t | #f
    exp ::= arg | (op arg*) | (let ([x exp]) exp) | (if exp exp exp)
    R2 ::= (program ((type . type)) exp)

create-CFG
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V

    arg ::= x | n | #t | #f
    exp ::= arg | (op arg*)
    tail ::= (jump label) | (if (rel-op exp*) label label) | (return exp)
	         | (stmt . tail)
    stmt ::= (assign x exp)
    CFG ::= (program ((type . type) (flow-graph . ([label . tail]*))) tail)

optimize-jumps
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V

    same grammar as above

uncover-locals
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V

    arg ::= x | n | #t | #f
    exp ::= arg | (op arg*)
    tail ::= (return exp) | (stmt . tail)
	      | (goto label) | (if (op exp*) (goto label) (goto label))
    stmt ::= (assign x exp)
    CFG ::= (program ((locals . x*) (type . type)
	                  (flow-graph . ([label . tail]*)))
				     tail)

select-instructions
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V

    imm ::= (var x) | (deref r n) | (int n)
    instr ::= (addq imm imm) | (jmp label) | (jmp-if cc label) | (retq)
    x86-CFG ::= (program ((locals . x*) (type . type) 
	                      (flow-graph . ([label . instr*]*))
					     instr*)

uncover-live
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V

    imm ::= (var x) | (deref r n) | (int n)
    instr ::= (addq imm imm) | (jmp label) | (jmp-if cc label) | (retq)
	block ::= (block (lives ls*) instr*)
    x86-CFG ::= (program ((locals . x*) (type . type)
	                      (flow-graph . ([label . block]*))) block)

build-interference
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V

    x86-CFG ::= (program ((locals . x*) (type . type)
	                      (flow-graph . ([label . block]*))
						  (conflicts . graph))
					     block)

allocate-registers
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V

    imm ::= (reg r) | (deref r n) | (int n)
    instr ::= (addq imm imm) | (jmp label) | (jmp-if cc label label) | (retq)
    x86-CFG ::= (program (x ...) (type type) ([label . instr*]*) instr*)
    
print-x86
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V