On 3/28/14, 2:16 PM, Chris Peterson wrote:
warp is Facebook's new C/C++ preprocessor, written by Walter Bright (in
D, of course). They claim build time (not just preprocessing time) of
10% to 40%.
https://code.facebook.com/posts/476987592402291/under-the-hood-warp-a-fast-c-and-c-preprocessor
I have a patch at
https://hg.stage.mozaws.net/gecko-collab/rev/d6ea4c36aa65 that will
change the build system to measure different phases of compiler
execution. For each compile command, it essentially runs -E +
-fsyntax-only + -c as separate commands and measures the results.
I'm not sure if isolating the run time of -E is sufficient to measure
the performance overhead of the preprocessor. But what I do know is that
the last time I ran this (a few months ago), mozilla-central's problem
was in AST generation and codegen, not preprocessor. I believe -E
processes were only a few ms on average (assuming SSD, which you should
all be using if you have a choice - MoCo employees have a choice) and
AST/codegen were an order of magnitude longer.
I encourage people to play around with this patch to measure things.
Better yet, try to hook up Warp and see if it actually makes a
difference. If it does, then by all means let's integrate it into the
build system like we already do with ccache.
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