On Wed, Jun 24, 2020 at 01:53:52PM -0700, Nick Desaulniers wrote:

On Wed, Jun 24, 2020 at 1:32 PM Sami Tolvanen [off-list ref] wrote:

quoted

diff --git a/Makefile b/Makefile
index ac2c61c37a73..0c7fe6fb2143 100644
--- a/Makefile
+++ b/Makefile

@@ -886,6 +886,22 @@ KBUILD_CFLAGS      += $(CC_FLAGS_SCS)
 export CC_FLAGS_SCS
 endif

+ifdef CONFIG_LTO_CLANG
+ifdef CONFIG_THINLTO
+CC_FLAGS_LTO_CLANG := -flto=thin $(call cc-option, -fsplit-lto-unit)

The kconfig change gates this on clang-11; do we still need the
cc-option check here, or can we hardcode the use of -fsplit-lto-unit?
Playing with the flag in godbolt, it looks like clang-8 had support
for this flag.

True, we don't need cc-option here anymore. I'll remove it, thanks.

quoted

+KBUILD_LDFLAGS += --thinlto-cache-dir=.thinlto-cache

It might be nice to have `make distclean` or even `make clean` scrub
the .thinlto-cache?  Also, I verified that the `.gitignore` rule for
`.*` properly ignores this dir.

Sure, distclean sounds appropriate to me.

Sami

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