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platform_build_soong
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Add opt-in option to turn on ThinLTO caching 

Allow developers to enable ThinLTO caching on their local build by
setting USE_THINLTO_CACHE environment variable.

This significantly speeds up incremental ThinLTO builds by caching
intermediate results. An incremental ART build (by `touch
compiler/compiler.cc`) reduced from 01:32 to 00:45.

We put the cache under out/soong/thinlto-cache as the cache can be
valid across different targets, and allows us to set a global cache
pruning policy.

The current cache policy is sufficient for current list of
ThinLTO-enabled projects, we can tune it up/down in the future.

Test: USE_THINLTO_CACHE=true m
Bug: 62839002
Change-Id: I4838fe833a1d8fbc73d743da6d19e3698dc89600
This commit is contained in:
Yi Kong 2018-02-16 20:36:16 +08:00
parent a052599bb6
commit 8aeaa7158a
1 changed files with 15 additions and 0 deletions
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15
cc/lto.go
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@ -74,12 +74,27 @@ func (lto *lto) flags(ctx BaseModuleContext, flags Flags) Flags {
var ltoFlag string var ltoFlag string
if Bool(lto.Properties.Lto.Thin) { if Bool(lto.Properties.Lto.Thin) {
ltoFlag = "-flto=thin" ltoFlag = "-flto=thin"
} else { } else {
ltoFlag = "-flto" ltoFlag = "-flto"
} }
flags.CFlags = append(flags.CFlags, ltoFlag) flags.CFlags = append(flags.CFlags, ltoFlag)
flags.LdFlags = append(flags.LdFlags, ltoFlag) flags.LdFlags = append(flags.LdFlags, ltoFlag)
if ctx.Config().IsEnvTrue("USE_THINLTO_CACHE") && Bool(lto.Properties.Lto.Thin) {
// Set appropriate ThinLTO cache policy
cacheDirFormat := "-Wl,-plugin-opt,cache-dir="
cacheDir := android.PathForOutput(ctx, "thinlto-cache").String()
flags.LdFlags = append(flags.LdFlags, cacheDirFormat+cacheDir)
// Limit the size of the ThinLTO cache to the lesser of 10% of available
// disk space and 10GB.
cachePolicyFormat := "-Wl,-plugin-opt,cache-policy="
policy := "cache_size=10%:cache_size_bytes=10g"
flags.LdFlags = append(flags.LdFlags, cachePolicyFormat+policy)
}
if ctx.Device() { if ctx.Device() {
// Work around bug in Clang that doesn't pass correct emulated // Work around bug in Clang that doesn't pass correct emulated
// TLS option to target. See b/72706604 or // TLS option to target. See b/72706604 or