Harpoon Project Compiler Intermediate Representation

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0 % = ( The following Quads modify the control-flow: , G ) Control flow merges at PHI nodes. A phi PHI(F node represents a list 0 of -functions of the form GIH D GJHLK M GIHON F'H P where is the arity of 0 the -function; that is, the number of predecessors to the node. Any non-negative number of predecessors, one successor. ) Conditional jump based on the boolean F . CJMP(F F If is false (0), control flows to the first successor (next[0]). F If is true (1), control flows to the second successor (next[1]). One predecessor, two successors. SWITCH(F , Q ) Indexed jump. Depending on the value of index F variable and a key Q list , control is transferred F )R3ST F E to F Q"E where . If does not match any key in Q , control is transferred to the F )R3ST F EU K default Q E where is the F last key in the key list. One predecessor, multiple successors. ) Return an optional value F from this RETURN(F method. One predecessor, one successor. The single successor should be a FOOTER node. ) Throws an exception F as the result of THROW(F this method. One predecessor, one successor. The single successor should be a FOOTER node. The remaining Quads have no effect on control flow, and have exactly one predecessor and one successor. No exceptions are thrown. K , , G ) Creates a new uninitialized array ANEW(F with type and dimensions § M GJE , storing a GZD reference § K in . The number of dimensions F supplied G in list may be smaller than the number of dimensions of array class type , in which case only § the dimensions specified G in will be 1 created. K , FWV , F,X ) Sets the element at index F,V of array to the value F,X in ASET(F F K . , , , , ) Calls method T [ of optional CALL([ F C class reference with R D C E parameter list , F C putting the return value in if no exception is thrown, or setting to the thrown exception. R Either or will be null on completion of the CALL. Exception T is not automatically thrown from the method containing the R CALL: T must be explicitly tested and its T exception rethrown if that T behavior is desired. is F not needed for static methods. , F V , F X ) Puts the boolean COMPONENTOF(F\K value true (1) F\K in if F X object is an instance of the component type of FWV array , or false (0) otherwise. , , ] ) Assigns numeric or string constant CONST(F of type § to variable F . ] § , B , F V ) Puts the value of field B of optional GET(FYK F V object in F\K variable F V . is not necessary for static fields. , V , ) Puts the boolean value INSTANCEOF(F\K F true § (1) in F V if object is an instance of class F\K , or false (0) otherwise. § K , FWV , F'X ) Fetches the element at index F,X AGET(F from FWV array and stores the value F K in . K , F,V ) Puts the length of array FWV into ALENGTH(F FYK variable . MOVE(F K , FWV ) Copies the value in F,V into F K . , ) Create a new uninitialized instance of NEW(F class , storing a reference in § . A class con- F § 4
structor must be invoked using CALL in order to initialize the instance. NOP( ) Performs no operation. , F , G ) Performs operation ^ on the variables OPER(^ in G list , storing the result F in . The operation is represented as a string; figure 3 lists all valid operation strings. The operations performed by the strings are identical to the operations performed by the Java bytecode operation of the same name, except that no exceptions are ever thrown. See [LY96] for details. , F\K , F V ) Sets field B of optional object F\K to SET(B the value F V of F\K . is not necessary for static fields. The harpoon.IR.QuadSSA.Code class provides a means to access the QuadSSA form of a given method; see the definition of superclass harpoon.ClassFile.HCode and the example code in harpoon.Main.Main for details. References [App98] Andrew W. Appel. Modern <strong>Compiler</strong> Implementation in Java. Cambridge University Press, 1998. [LY96] Tim Lindholm and Frank Yellin. The Java Virtual Machine Specification. Addison-Wesley, September 1996. Online at http://www.javasoft.com/ docs/books/vmspec. 5
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Harpoon Project Compiler Intermediate Representation

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