| 摘要 |
Reducing the number of overflow and underflow exception traps generated during the execution of a program on a computer that uses a top-of-stack cache, e.g. in a register window file architecture whereby the top of the stack is maintained in registers directly accessible by the CPU and the rest of the stack is maintained in memory. Rather than spilling/filling a fixed number of stack elements from/to the top-of stack cache to/from memory in response to an overflow or underflow trap respectively, which is inefficient when there are deeply nested or recursive subroutine calls, the number of stack elements spilled or filled is controlled by a predictor value. The predictor value reflects the history of the trap exceptions, such that if more overflow traps than underflow traps have occurred, more stack elements are spilled to memory on each overflow trap. Different predictor values can select different overflow and underflow vectors (Fig. 4), or a hash mechanism (Fig. 6) enables multiple predictors to separately control the spill/fill of the stack file dependant on where in memory the exceptions occur.
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