Syntactic Features for the Static Prediction of Silent Stores

We have organized our 131 features into nine categories. Out of the 131 features, 99 have been observed in our benchmarks. We describe each category, and their elements, in this page. Each category concerns different aspects of a store instruction such as L: p[i] = v. This syntax describes an instruction at program point L, which deposits a value v onto memory location p[i].

ValueType

This category of features concerns the type of the value v that will be stored in memory. In total, we have defined 17 different features in this category, but only four of them have been observed during profiling.

ValueSize

This category refers to the size of the value v, in bits, that shall be stored in memory. This size is only well-defined for fixed-size types like integers, floats and pointers. Integers can have different bitwidths, but, for instance, a type integer of 8 bits has always 8 bits of width.

ValueDeps

This category concerns the program slice that contributes to form the value v that shall be deposited in memory. The program slice of v is every statement that needs to be executed so that we can have v's value.

ValueOrigin

These features concern the last instruction that is used to produce the value v.

ValueRange

This category of features concerns the quantity of different values that v can assume. To compute this value, we reuse an old implementation of range analysys.

PointerType

This category of features concerns the type of the pointer p that is used as the target of the store operation.

PointerLoc

This category of features concern the location of the region pointed by p. The typical locations are the heap, the stack, and the static memory area. However, sometimes we cannot determine this location, and thus we fall back to tracking from which instruction the location came from. Perhaps, the best would be to split this category into two new groups: memory location, and origin of the pointer.

LabelLoc

This category concerns the location of the store instruction in the program. In other words, it is all about the location L of the store operation. It deals, for instance, with dominance and post-dominance relations, and with the number of successors and predecessors of the basic blocks that contain the store instruction.

PointerStride

This category concerns the stride of the variable i used to index the memory location where the store happens. The stride is the increment on the variable, whenever it can be determined statically.