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Simplify LTO flags handling

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... and add more comments about the use of --lto-O0.

Test: presubmit
Change-Id: I2ef7bf4f100a8d7559a6b738e9211c596d579dc6
This commit is contained in:
Yi Kong
2023-07-03 16:59:33 +09:00
parent 222995b2c1
commit b9d5046d8b
1 changed files with 18 additions and 17 deletions
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35
cc/lto.go
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@@ -76,43 +76,44 @@ func (lto *lto) flags(ctx BaseModuleContext, flags Flags) Flags {
return flags
}
if lto.Properties.LtoEnabled {
var ltoCFlag string
var ltoLdFlag string
if lto.ThinLTO() {
ltoCFlag = "-flto=thin -fsplit-lto-unit"
} else {
ltoCFlag = "-flto=thin -fsplit-lto-unit"
ltoLdFlag = "-Wl,--lto-O0"
ltoCFlags := []string{"-flto=thin", "-fsplit-lto-unit"}
var ltoLdFlags []string
// The module did not explicitly turn on LTO. Only leverage LTO's
// better dead code elinmination and CFG simplification, but do
// not perform costly optimizations for a balance between compile
// time, binary size and performance.
if !lto.ThinLTO() {
ltoLdFlags = append(ltoLdFlags, "-Wl,--lto-O0")
}
flags.Local.CFlags = append(flags.Local.CFlags, ltoCFlag)
flags.Local.AsFlags = append(flags.Local.AsFlags, ltoCFlag)
flags.Local.LdFlags = append(flags.Local.LdFlags, ltoCFlag)
flags.Local.LdFlags = append(flags.Local.LdFlags, ltoLdFlag)
if Bool(lto.Properties.Whole_program_vtables) {
flags.Local.CFlags = append(flags.Local.CFlags, "-fwhole-program-vtables")
ltoCFlags = append(ltoCFlags, "-fwhole-program-vtables")
}
if ctx.Config().IsEnvTrue("USE_THINLTO_CACHE") {
// Set appropriate ThinLTO cache policy
cacheDirFormat := "-Wl,--thinlto-cache-dir="
cacheDir := android.PathForOutput(ctx, "thinlto-cache").String()
flags.Local.LdFlags = append(flags.Local.LdFlags, cacheDirFormat+cacheDir)
ltoLdFlags = append(ltoLdFlags, cacheDirFormat+cacheDir)
// Limit the size of the ThinLTO cache to the lesser of 10% of available
// disk space and 10GB.
cachePolicyFormat := "-Wl,--thinlto-cache-policy="
policy := "cache_size=10%:cache_size_bytes=10g"
flags.Local.LdFlags = append(flags.Local.LdFlags, cachePolicyFormat+policy)
ltoLdFlags = append(ltoLdFlags, cachePolicyFormat+policy)
}
// If the module does not have a profile, be conservative and limit cross TU inline
// limit to 5 LLVM IR instructions, to balance binary size increase and performance.
if !ctx.Darwin() && !ctx.isPgoCompile() && !ctx.isAfdoCompile() {
flags.Local.LdFlags = append(flags.Local.LdFlags,
"-Wl,-plugin-opt,-import-instr-limit=5")
ltoLdFlags = append(ltoLdFlags, "-Wl,-plugin-opt,-import-instr-limit=5")
}
flags.Local.CFlags = append(flags.Local.CFlags, ltoCFlags...)
flags.Local.AsFlags = append(flags.Local.AsFlags, ltoCFlags...)
flags.Local.LdFlags = append(flags.Local.LdFlags, ltoCFlags...)
flags.Local.LdFlags = append(flags.Local.LdFlags, ltoLdFlags...)
}
return flags
}