I was playing around with different optimizations of sim-compile... we know that compile time is a big problem as the design scales, and so I was looking into auto-extraction of procedures but a VERY funny thing is happening. In the past I guess I just assumed that -O0 would be the fasted compile time (I mean it make sense right? no optimizations?) but here is what I foud.
At -O0, function extraction helps compile time (482s → 178-190s) but bloats .so and hurts sim time due to unoptimized function call overhead (boo!) so then I tried it with -O1.
Just switching to -O1 takes vanilla baseline compile time from 482s to 4.3s — a 112x speedup in compile time! The .so drops from 807K to 145K and sim is also 12x faster. GCC's own optimizer at -O1 does everything our extraction does and more.
At -O1, function extraction seems to actively hurt — compile goes from 4.3s to 20-23s (the extra function definitions give GCC more to analyze), while .so and sim are essentially unchanged.
I have not tested this rigorously, but for 100x compile time speed up for a 1 byte change to the source code seems like a tradeoff worth investigating :)
I was playing around with different optimizations of sim-compile... we know that compile time is a big problem as the design scales, and so I was looking into auto-extraction of procedures but a VERY funny thing is happening. In the past I guess I just assumed that -O0 would be the fasted compile time (I mean it make sense right? no optimizations?) but here is what I foud.
At -O0, function extraction helps compile time (482s → 178-190s) but bloats .so and hurts sim time due to unoptimized function call overhead (boo!) so then I tried it with -O1.
Just switching to -O1 takes vanilla baseline compile time from 482s to 4.3s — a 112x speedup in compile time! The .so drops from 807K to 145K and sim is also 12x faster. GCC's own optimizer at -O1 does everything our extraction does and more.
At -O1, function extraction seems to actively hurt — compile goes from 4.3s to 20-23s (the extra function definitions give GCC more to analyze), while .so and sim are essentially unchanged.
I have not tested this rigorously, but for 100x compile time speed up for a 1 byte change to the source code seems like a tradeoff worth investigating :)