Rollup merge of #44675 - alexcrichton:many-cgu, r=aidanhs

ci: Use multiple codegen units on non-dist bots

This commit is yet another attempt to bring down our cycle times by
parallelizing some of the long-and-serial parts of the build, for example
optimizing the libsyntax, librustc, and librustc_driver crate. The hope is that
any perf loss from codegen units is more than made up for with the perf gain
from using multiple codegen units.

The value of 16 codegen units here is pretty arbitrary, it's basically just a
number which hopefully means that the cores are always nice and warm.

Author: alexcrichton

src/bootstrap/configure.py

@@ -256,6 +256,8 @@ def set(key, value):
                 value = True
             elif keyval[1] == "false":
                 value = False
+            elif keyval[1].isdigit():
+                value = int(keyval[1])
             else:
                 value = keyval[1]
             set(keyval[0], value)
@@ -357,6 +359,8 @@ def to_toml(value):
         return '[' + ', '.join(map(to_toml, value)) + ']'
     elif isinstance(value, str):
         return "'" + value + "'"
+    elif isinstance(value, int):
+        return str(value)
     else:
         raise 'no toml'
 

src/ci/run.sh

@@ -52,6 +52,10 @@ if [ "$DEPLOY$DEPLOY_ALT" != "" ]; then
     RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --disable-llvm-assertions"
   fi
 else
+  # Let's try to take advantage of some of those sweet sweet parallelism wins by
+  # using multiple codegen units during the bootstrap
+  RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --set rust.codegen-units=16"
+
   # We almost always want debug assertions enabled, but sometimes this takes too
   # long for too little benefit, so we just turn them off.
   if [ "$NO_DEBUG_ASSERTIONS" = "" ]; then