linux-kernel - [PATCH v2 4/4] kbuild: Add config to assert profile accuracy for aggressive optimization

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Message-ID: <20251014191156.3836703-5-xur@google.com>
Date: Tue, 14 Oct 2025 19:11:56 +0000
From: xur@...gle.com
To: Alexey Gladkov <legion@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, 
	Ard Biesheuvel <ardb@...nel.org>, Bill Wendling <morbo@...gle.com>, Han Shen <shenhan@...gle.com>, 
	Ingo Molnar <mingo@...nel.org>, Josh Poimboeuf <jpoimboe@...nel.org>, 
	Justin Stitt <justinstitt@...gle.com>, Kees Cook <kees@...nel.org>, 
	Linus Walleij <linus.walleij@...aro.org>, Masahiro Yamada <masahiroy@...nel.org>, 
	Miguel Ojeda <ojeda@...nel.org>, Nathan Chancellor <nathan@...nel.org>, 
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>, Nicolas Schier <nicolas.schier@...ux.dev>, 
	Peter Zijlstra <peterz@...radead.org>, Tamir Duberstein <tamird@...il.com>, 
	Thomas Gleixner <tglx@...utronix.de>, 
	"Thomas Weißschuh" <thomas.weissschuh@...utronix.de>, Yabin Cui <yabinc@...gle.com>, 
	Sriraman Tallam <tmsriram@...gle.com>
Cc: linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org, 
	llvm@...ts.linux.dev, Rong Xu <xur@...gle.com>
Subject: [PATCH v2 4/4] kbuild: Add config to assert profile accuracy for
 aggressive optimization

From: Rong Xu <xur@...gle.com>

Adds a build config to AutoFDO to assert that the generated profile
accurately represents the intended workload. This enables Clang to
perform more aggressive optimizations.

Signed-off-by: Rong Xu <xur@...gle.com>
---
 arch/Kconfig             | 11 +++++++++++
 scripts/Makefile.autofdo |  3 +++
 2 files changed, 14 insertions(+)

diff --git a/arch/Kconfig b/arch/Kconfig
index ebe08b9186adc..6fdc676cb0fe4 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -886,6 +886,17 @@ config AUTOFDO_CLANG
 
 	  If unsure, say N.
 
+config AUTOFDO_PROFILE_ACCURATE
+	bool "Assert AutoFDO profile is accurate (EXPERIMENTAL)"
+	depends on AUTOFDO_CLANG
+	help
+	  This option asserts that the AutoFDO profile (specified
+	  in CLANG_AUTOFDO_PROFILE) is collected from a representative
+	  workload, allowing the Clang compiler to perform more
+	  aggressive optimizations.
+
+	  If unsure, say N.
+
 config ARCH_SUPPORTS_PROPELLER_CLANG
 	bool
 
diff --git a/scripts/Makefile.autofdo b/scripts/Makefile.autofdo
index 5bcfcef273745..36abeae2accdc 100644
--- a/scripts/Makefile.autofdo
+++ b/scripts/Makefile.autofdo
@@ -11,6 +11,9 @@ endif
 ifdef CLANG_AUTOFDO_PROFILE
   CFLAGS_AUTOFDO_CLANG += -fprofile-sample-use=$(CLANG_AUTOFDO_PROFILE) -ffunction-sections
   CFLAGS_AUTOFDO_CLANG += -fsplit-machine-functions
+ifdef CONFIG_AUTOFDO_PROFILE_ACCURATE
+  CFLAGS_AUTOFDO_CLANG += -fprofile-sample-accurate
+endif
 endif
 
 ifdef CONFIG_LTO_CLANG_THIN
-- 
2.51.0.788.g6d19910ace-goog