From: Ian Rogers <irogers@google.com>
To: irogers@google.com, acme@kernel.org, james.clark@linaro.org,
namhyung@kernel.org
Cc: 9erthalion6@gmail.com, adrian.hunter@intel.com, alex@ghiti.fr,
alexandre.chartre@oracle.com, andrii@kernel.org,
ankur.a.arora@oracle.com, aou@eecs.berkeley.edu,
bpf@vger.kernel.org, collin.funk1@gmail.com,
costa.shul@redhat.com, daniel@iogearbox.net,
dapeng1.mi@linux.intel.com, dsterba@suse.com, eddyz87@gmail.com,
howardchu95@gmail.com, jolsa@kernel.org, leo.yan@arm.com,
linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
martin.lau@linux.dev, memxor@gmail.com, mingo@redhat.com,
mmayer@broadcom.com, nathan@kernel.org, palmer@dabbelt.com,
peterz@infradead.org, pjw@kernel.org, qmo@kernel.org,
ricky.ringler@proton.me, song@kernel.org,
swapnil.sapkal@amd.com, terrelln@fb.com, tglozar@redhat.com,
thomas.falcon@intel.com, yonghong.song@linux.dev
Subject: [PATCH v2 04/18] tools scripts: Short-circuit CC_NO_CLANG compiler probe in Makefile.include
Date: Tue, 12 May 2026 10:46:24 -0700 [thread overview]
Message-ID: <20260512174638.120445-5-irogers@google.com> (raw)
In-Reply-To: <20260512174638.120445-1-irogers@google.com>
In Makefile.include, CC_NO_CLANG unconditionally executed a GCC/Clang
compiler inspection fork (gcc -dM -E ...) during Makefile parse time.
Because Makefile.include is included across more than 40 sub-makes and
component directories throughout the Kbuild tree, Make continuously
re-executed this compiler probe dozens of times during incremental builds.
Wrap CC_NO_CLANG with a conditional check and export the variable to
sub-makes. This guarantees Kbuild evaluates the compiler backend exactly
once during top-level Make invocation, eliminating 40+ redundant shell forks
across the build tree.
Assisted-by: Gemini:gemini-3.1-pro-preview
Signed-off-by: Ian Rogers <irogers@google.com>
---
tools/scripts/Makefile.include | 3 +++
1 file changed, 3 insertions(+)
diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
index 41971a68972d..3c7803122ae2 100644
--- a/tools/scripts/Makefile.include
+++ b/tools/scripts/Makefile.include
@@ -74,7 +74,10 @@ $(call allow-override,CXX,$(CROSS_COMPILE)g++)
$(call allow-override,STRIP,$(CROSS_COMPILE)strip)
endif
+ifeq ($(CC_NO_CLANG),)
CC_NO_CLANG := $(shell $(CC) -dM -E -x c /dev/null | grep -Fq "__clang__"; echo $$?)
+endif
+export CC_NO_CLANG
ifneq ($(LLVM),)
HOSTAR ?= $(LLVM_PREFIX)llvm-ar$(LLVM_SUFFIX)
--
2.54.0.563.g4f69b47b94-goog
next prev parent reply other threads:[~2026-05-12 17:46 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-12 5:35 [PATCH v1 00/14] perf build: Reduce build time by one third Ian Rogers
2026-05-12 5:35 ` [PATCH v1 01/14] bpftool build: Restrict feature tests during bootstrap compilation Ian Rogers
2026-05-12 5:35 ` [PATCH v1 02/14] perf trace beauty: Make beauty generated C code standalone .o files Ian Rogers
2026-05-12 5:35 ` [PATCH v1 03/14] perf build: Decouple pmu-events from prepare umbrella target Ian Rogers
2026-05-12 5:35 ` [PATCH v1 04/14] perf build: Remove empty archheaders target Ian Rogers
2026-05-12 5:35 ` [PATCH v1 05/14] perf build: Move BPF skeleton generation out of Makefile.perf Ian Rogers
2026-05-12 5:35 ` [PATCH v1 06/14] perf build: Encapsulate vmlinux.h and bpftool in bpf_skel.mak Ian Rogers
2026-05-12 5:35 ` [PATCH v1 07/14] perf build: Move static libbpf dependency out of prepare step Ian Rogers
2026-05-12 5:35 ` [PATCH v1 08/14] perf build: Pre-generate BPF skeletons during umbrella prepare phase Ian Rogers
2026-05-12 5:35 ` [PATCH v1 09/14] perf build: Move libsymbol dependency out of prepare step Ian Rogers
2026-05-12 5:35 ` [PATCH v1 10/14] perf build: Remove redundant libbpf feature check for static builds Ian Rogers
2026-05-12 5:35 ` [PATCH v1 11/14] tools build: Integrate libdebuginfod into test-all fast path Ian Rogers
2026-05-12 5:35 ` [PATCH v1 12/14] perf pmu-events: Split big_c_string storage into standalone compilation unit Ian Rogers
2026-05-12 5:35 ` [PATCH v1 13/14] perf pmu-events: Parallelize JSON and metric pre-computation in jevents.py Ian Rogers
2026-05-12 5:35 ` [PATCH v1 14/14] perf build: Prefix SCRIPTS with output directory to fix continuous rebuilds Ian Rogers
2026-05-12 17:46 ` [PATCH v2 00/18] perf build: Reduce build time by nearly half Ian Rogers
2026-05-12 17:46 ` [PATCH v2 01/18] bpftool build: Restrict feature tests during bootstrap compilation Ian Rogers
2026-05-12 17:46 ` [PATCH v2 02/18] tools build: Integrate libdebuginfod into test-all fast path Ian Rogers
2026-05-12 17:46 ` [PATCH v2 03/18] tools build: Fix test-clang-bpf-co-re.bin to generate target file Ian Rogers
2026-05-12 17:46 ` Ian Rogers [this message]
2026-05-12 17:46 ` [PATCH v2 05/18] perf trace beauty: Make beauty generated C code standalone .o files Ian Rogers
2026-05-12 17:46 ` [PATCH v2 06/18] perf build: Decouple pmu-events from prepare umbrella target Ian Rogers
2026-05-12 17:46 ` [PATCH v2 07/18] perf build: Remove empty archheaders target Ian Rogers
2026-05-12 17:46 ` [PATCH v2 08/18] perf build: Move BPF skeleton generation out of Makefile.perf Ian Rogers
2026-05-12 17:46 ` [PATCH v2 09/18] perf build: Encapsulate vmlinux.h and bpftool in bpf_skel.mak Ian Rogers
2026-05-12 17:46 ` [PATCH v2 10/18] perf build: Move static libbpf dependency out of prepare step Ian Rogers
2026-05-12 17:46 ` [PATCH v2 11/18] perf build: Pre-generate BPF skeleton tooling during umbrella prepare phase Ian Rogers
2026-05-12 17:46 ` [PATCH v2 12/18] perf build: Move libsymbol dependency out of prepare step Ian Rogers
2026-05-12 17:46 ` [PATCH v2 13/18] perf build: Remove redundant libbpf feature check for static builds Ian Rogers
2026-05-12 17:46 ` [PATCH v2 14/18] perf pmu-events: Split big_c_string storage into standalone compilation unit Ian Rogers
2026-05-12 17:46 ` [PATCH v2 15/18] perf pmu-events: Parallelize JSON and metric pre-computation in jevents.py Ian Rogers
2026-05-12 17:46 ` [PATCH v2 16/18] perf build: Prefix SCRIPTS with output directory to fix continuous rebuilds Ian Rogers
2026-05-12 17:46 ` [PATCH v2 17/18] perf pmu-events: Convert recursive shell assignments and macros to Make built-ins Ian Rogers
2026-05-12 17:46 ` [PATCH v2 18/18] perf build: Convert llvm-config shell queries to simply expanded variables Ian Rogers
2026-05-12 9:36 ` [PATCH v1 00/14] perf build: Reduce build time by one third James Clark
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