| java.lang.Object
 org.apache.bcel.util.InstructionFinder
| InstructionFinder | | public class InstructionFinder (Code) | | InstructionFinder is a tool to search for given instructions patterns, i.e.,
match sequences of instructions in an instruction list via regular
expressions. This can be used, e.g., in order to implement a peep hole
optimizer that looks for code patterns and replaces them with faster
equivalents.
This class internally uses the
Regexp package to search for regular expressions.
A typical application would look like this:
InstructionFinder f = new InstructionFinder(il);
String pat = "IfInstruction ICONST_0 GOTO ICONST_1 NOP (IFEQ|IFNE)";
for(Iterator i = f.search(pat, constraint); i.hasNext(); ) {
InstructionHandle[] match = (InstructionHandle[])i.next();
...
il.delete(match[1], match[5]);
...
}
version:
$Id: InstructionFinder.java 386056 2006-03-15 11:31:56Z tcurdt $
author:
M. Dahm
See Also: Instruction
See Also: InstructionList |
| Inner Class :public static interface CodeConstraint | |
| InstructionFinder | | public InstructionFinder(InstructionList il)(Code) | |
Parameters:
il - instruction list to search for given patterns |
| reread | | final public void reread()(Code) | | Reread the instruction list, e.g., after you've altered the list upon a
match.
|
| search | | final public Iterator search(String pattern, InstructionHandle from, CodeConstraint constraint)(Code) | | Search for the given pattern in the instruction list. You can search for
any valid opcode via its symbolic name, e.g. "istore". You can also use a
super class or an interface name to match a whole set of instructions, e.g.
"BranchInstruction" or "LoadInstruction". "istore" is also an alias for all
"istore_x" instructions. Additional aliases are "if" for "ifxx", "if_icmp"
for "if_icmpxx", "if_acmp" for "if_acmpxx".
Consecutive instruction names must be separated by white space which will
be removed during the compilation of the pattern.
For the rest the usual pattern matching rules for regular expressions
apply.
Example pattern:
search("BranchInstruction NOP ((IfInstruction|GOTO)+ ISTORE Instruction)*");
If you alter the instruction list upon a match such that other matching
areas are affected, you should call reread() to update the finder and call
search() again, because the matches are cached.
Parameters:
pattern - the instruction pattern to search for, where case is ignored
Parameters:
from - where to start the search in the instruction list
Parameters:
constraint - optional CodeConstraint to check the found code pattern foruser-defined constraints iterator of matches where e.nextElement() returns an array ofinstruction handles describing the matched area |
| search | | final public Iterator search(String pattern)(Code) | | Start search beginning from the start of the given instruction list.
Parameters:
pattern - the instruction pattern to search for, where case is ignored iterator of matches where e.nextElement() returns an array ofinstruction handles describing the matched area |
| search | | final public Iterator search(String pattern, InstructionHandle from)(Code) | | Start search beginning from `from'.
Parameters:
pattern - the instruction pattern to search for, where case is ignored
Parameters:
from - where to start the search in the instruction list iterator of matches where e.nextElement() returns an array ofinstruction handles describing the matched area |
| search | | final public Iterator search(String pattern, CodeConstraint constraint)(Code) | | Start search beginning from the start of the given instruction list. Check
found matches with the constraint object.
Parameters:
pattern - the instruction pattern to search for, case is ignored
Parameters:
constraint - constraints to be checked on matching code instruction handle or `null' if the match failed |
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