Optimizations

The following wildcards are supported:

?	matches any single character in an optimization name.
*	matches any part of an optimization name.

An optimization that is preceded by an exclamation mark '!' is excluded from further attempts to match with subsequent optimization names in the filter. Make sure to specify filters correctly, since they are not checked for potential typos.

For example, "code/simplification/variable,code/simplification/arithmetic" only performs the two specified peephole optimizations.

For example, "!method/propagation/*" performs all optimizations, except the ones that propagate values between methods.

For example, "!code/simplification/advanced,code/simplification/*" only performs all peephole optimizations.

Some optimizations necessarily imply other optimizations. These are then indicated. Note that the list is likely to change for newer versions, as optimizations are added and reorganized.

class/marking/final

Marks classes as final, whenever possible.

class/unboxing/enum

Simplifies enum types to integer constants, whenever possible.

class/merging/vertical

Merges classes vertically in the class hierarchy, whenever possible.

class/merging/horizontal

Merges classes horizontally in the class hierarchy, whenever possible.

(⇒ code/removal/advanced)

field/removal/writeonly

Removes write-only fields.

field/marking/private

Marks fields as private, whenever possible.

field/specialization/type

Specializes the types of fields, whenever possible.

(⇒ code/simplification/advanced)

field/propagation/value

Propagates the values of fields across methods.

method/marking/private

Marks methods as private, whenever possible (devirtualization).

(⇒ code/removal/advanced)

method/marking/static

Marks methods as static, whenever possible (devirtualization).

method/marking/final

Marks methods as final, whenever possible.

method/marking/synchronized

Unmarks methods as synchronized, whenever possible.

(⇒ code/removal/advanced)

method/removal/parameter

Removes unused method parameters.

method/specialization/parametertype

Specializes the types of method parameters, whenever possible.

method/specialization/returntype

Specializes the types of method return values, whenever possible.

(⇒ code/simplification/advanced)

method/propagation/parameter

Propagates the values of method parameters from method invocations to the invoked methods.

(⇒ code/simplification/advanced)

method/propagation/returnvalue

Propagates the values of method return values from methods to their invocations.

method/inlining/short

Inlines short methods.

method/inlining/unique

Inlines methods that are only called once.

method/inlining/tailrecursion

Simplifies tail recursion calls, whenever possible.

code/merging

Merges identical blocks of code by modifying branch targets.

code/simplification/variable

Performs peephole optimizations for variable loading and storing.

code/simplification/arithmetic

Performs peephole optimizations for arithmetic instructions.

code/simplification/cast

Performs peephole optimizations for casting operations.

code/simplification/field

Performs peephole optimizations for field loading and storing.

(⇒ code/removal/simple)

code/simplification/branch

Performs peephole optimizations for branch instructions.

code/simplification/string

Performs peephole optimizations for constant strings.

code/simplification/math

Performs peephole optimizations for Math method calls.

(best used with code/removal/advanced)

code/simplification/advanced

Simplifies code based on control flow analysis and data flow analysis.

(⇒ code/removal/exception)

code/removal/advanced

Removes dead code based on control flow analysis and data flow analysis.

(⇒ code/removal/exception)

code/removal/simple

Removes dead code based on a simple control flow analysis.

code/removal/variable

Removes unused variables from the local variable frame.

code/removal/exception

Removes exceptions with empty try blocks.

code/allocation/variable

Optimizes variable allocation on the local variable frame.

DexGuard also provides some unofficial settings to control optimizations, that may disappear in future versions. These are Java system properties, which can be set as JVM arguments (with -D.....):

maximum.inlined.code.length (default = 8 bytes)

Specifies the maximum code length (expressed in bytes) of short methods that are eligible to be inlined. Inlining methods that are too long may unnecessarily inflate the code size.

maximum.resulting.code.length (default = 8000 bytes for JSE, 2000 bytes for JME)

Specifies the maximum resulting code length (expressed in bytes) allowed when inlining methods. Many Java virtual machines do not apply just-in-time compilation to methods that are too long, so it's important not to let them grow too large.

optimize.conservatively (default = unset)

Allows input code with ordinary instructions intentionally throwing NullPointerException, ArrayIndexOutOfBoundsException, or ClassCastException, without any other useful purposes. By default, DexGuard may just discard such seemingly useless instructions, resulting in better optimization of most common code.