Lecture 13 intermediate code generation 2.pptx
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This document discusses code generation for control flow statements and boolean expressions in programming languages. It introduces type conversions, abstract syntax trees, control flow, and generating three-address code for booleans. A key technique discussed is backpatching, which allows saving instruction labels as indices and later inserting target addresses to avoid an extra pass for setting jump targets. An example shows applying backpatching to an annotated parse tree for a boolean expression.
Lecture 13 intermediate code generation 2.pptx
- 1. CSE 420 Intermediate Code Generation Lecture 13
- 2. Conversions between primitive typesConversions between primitive types in Javain Java
- 3. Introducing type conversions intoIntroducing type conversions into expression evaluationexpression evaluation
- 4. Abstract syntax tree for theAbstract syntax tree for the function definitionfunction definition fun length(x) = if null(x) then 0 else length(tl(x)+1) This is a polymorphic function in ML language
- 5. Control FlowControl Flow Boolean expressions are often used to: • Alter the flow of control. • Compute logical values.
- 9. Generating three-address code forGenerating three-address code for booleansbooleans
- 10. translation of a simple if-statementtranslation of a simple if-statement • •
- 11. BackpatchingBackpatching • Previous codes for Boolean expressions insert symbolic labels for jumps • It therefore needs a separate pass to set them to appropriate addresses • We can use a technique named backpatching to avoid this • We assume we save instructions into an array and labels will be indices in the array • For non-terminal B we use two attributes B.truelist and B.falselist together with following functions: ▫ makelist(i): create a new list containing only I, an index into the array of instructions ▫ Merge(p1,p2): concatenates the lists pointed by p1 and p2 and returns a pointer to the concatenated list ▫ Backpatch(p,i): inserts i as the target label for each of the instruction on the list pointed to by p
- 12. Backpatching for Boolean ExpressionsBackpatching for Boolean Expressions • •
- 13. Backpatching for Boolean ExpressionsBackpatching for Boolean Expressions • Annotated parse tree for x < 100 || x > 200 && x ! = y
- 15. Translation of a switch-statementTranslation of a switch-statement
- 16. Any Question?