Commits on Aug 1, 2019

1. clif-backend: Eliminate FunctionEnvironment construction in feed_event() …

   The feed_event() function is called for every wasm binary instruction.
   Let's optimize it by storing FunctionEnvironment object in
   CraneliftFunctionCodeGenerator, rather than constructing it for every
   feed_event() invocation.
   
   This change reduces the time to run "ngix compile" benchmark by 68%:
   
   Before:
   
     nginx compile           time:   [1.4152 s 1.4186 s 1.4222 s]
     Found 1 outliers among 10 measurements (10.00%)
       1 (10.00%) high mild
   
   After:
   
     nginx compile           time:   [447.76 ms 448.32 ms 448.80 ms]
                             change: [-68.542% -68.440% -68.352%] (p = 0.00 < 0.05)
                             Performance has improved.
   
   I assume some of the clone() calls are very expensive (Vec::clone(),
   likely). I did see libc malloc()/free() high up in "perf top" profiles,
   which are eliminted by this change.
   
   I also looked into eliminating FunctionBuilder construction from
   feed_event(). That turns out to be painful on lifetime rules because it
   borrows bunch of other objects, so I am leaving it for someone who knows
   the code better than I do.

   

   penberg committed Aug 1, 2019
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2. Merge branch 'master' into clif-backend

   

   bjfish authored Aug 1, 2019
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