Hi Richard, When -Os is used and the multiplier is of the for 2^N +- 1 we generate a MUL instruction rather that a shift-left N and add-sub 1. The problem is that rtx cost for the MUL is too cheap causing the shift-left and add-sub sequence to be more expensive. This patch makes the MUL slightly more expension so the alternate sequence and better sequence used. The shift + add/sub is faster and can probaly be scheduled better. This change is code size neutral because the MUL requires a load-immediate. ChangeLog: * config/mips/mips.c: (mips_rtx_costs): Slightly increase cost of MUL when optimizing for size. This allows a better sequence to be choosen when multiply by a constant of the form 2^N +- 1. Graham
mips.c.diff
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