Bitwidth aware global register allocation

Multimedia and network processing applications make extensive use of subword data. Since registers are capable of holding a full data word, when a subword variable is assigned a register, only part of the register is used. New embedded processors have started supporting instruction sets that allow direct referencing of bit sections within registers and therefore multiple subword variables can be made to simultaneously reside in the same register without hindering accesses to these variables. However, a new register allocation algorithm is needed that is aware of the bitwidths of program variables and is capable of packing multiple subword variables into a single register. This paper presents one such algorithm. The algorithm we propose has two key steps. First, a combination of forward and backward data flow analyses are developed to determine the bitwidths of program variables throughout the program. This analysis is required because the declared bitwidths of variables are often larg...

• Type: Conference
• Year: 2003
• Where: POPL
• Authors: Sriraman Tallam, Rajiv Gupta
• Keywords: Multiple Subword Variables, POPL 2003, Processors--compilers General Terms, Programming Languages, Register Allocation Algorithm