1. A method for selectively retrieving expressions from memory during compilation, comprising: scanning code for expressions that can be effectively accessed from highly cached memory without being loaded into registers, wherein scanning the code includes: creating a bit vector to represent a plurality of expressions in a code region; initializing bits of the bit vector as set such that the expressions in the code region are initially marked as candidates for retrieval from the highly cached memory; determining whether a first expression of the expressions in the code region is modified by the code; resetting a bit associated with the first expression, of the bit vector responsive to determining that the first expression is modified by the code; and traversing the code region, looking for uses of expressions for which the bits of the bit vector associated with the expressions in the code region have not been reset; and retrieving the expressions for which the bits have not been reset, that can be effectively accessed directly from the highly cached memory rather than loading the expressions for which the bits have not been reset into the registers.