Roger Sayle 于2023年12月29日周五 00:54写道：
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> The current (default) behavior is that when the target doesn’t define
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> TARGET_INSN_COST the middle-end uses the backend’s
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> TARGET_RTX_COSTS, so multiplications are slower than additions,
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> but about the same size when optimizing for size (with -O
The current (default) behavior is that when the target doesn't define
TARGET_INSN_COST the middle-end uses the backend's
TARGET_RTX_COSTS, so multiplications are slower than additions,
but about the same size when optimizing for size (with -Os or -Oz).
All of this gets disabled with your
MIPS backend had some information about INSN, including length,
count etc.
And since some instructions are more costly, let's add a new
attr `perf_ratio`. It's default value is (const_int 1).
The return value of mips_insn_cost is
insn_count * perf_ratio * 4.
The magic `4` here, is due to that
