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AFNElJ82Z2vrKtwsSEgGdUbsaBaDmRNsdzJ4CfOx/jct9batxj7iUyHqZgJtUO+yRM6qw0m93brpReNflP/yB2l146Wh@vger.kernel.org X-Gm-Message-State: AOJu0Yx9Tr09dJtZg4pVI7/nVkR2Wl3sUJ/6jHaUs54ynY2rQlROKoD7 Yl9ITtIWqZLEA+l/QuRiiKbAvtJ7TGEmQJMd3XywQ6gVRtcTmBKL95WkzYqZDqsMUH8XPXpcHfk /UKzbuAs/9g== X-Received: from dybia10.prod.google.com ([2002:a05:7301:30a:b0:2da:3d44:ddce]) (user=irogers job=prod-delivery.src-stubby-dispatcher) by 2002:a05:7300:5793:b0:2f2:6dde:df54 with SMTP id 5a478bee46e88-3011977f73fmr47297eec.33.1778608046462; Tue, 12 May 2026 10:47:26 -0700 (PDT) Date: Tue, 12 May 2026 10:46:38 -0700 In-Reply-To: <20260512174638.120445-1-irogers@google.com> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260512053539.3410189-15-irogers@google.com> <20260512174638.120445-1-irogers@google.com> X-Mailer: git-send-email 2.54.0.563.g4f69b47b94-goog Message-ID: <20260512174638.120445-19-irogers@google.com> Subject: [PATCH v2 18/18] perf build: Convert llvm-config shell queries to simply expanded variables From: Ian Rogers 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 Content-Type: text/plain; charset="UTF-8" In Makefile.config, CFLAGS, CXXFLAGS, LIBLLVM, and EXTLIBS were assigned using recursive expansion or appended with raw $(shell $(LLVM_CONFIG) ...) calls. Because these variables were expanded during dependency evaluation across every single object file compilation rule, Kbuild continuously re-executed llvm-config forks nearly 200 times during incremental builds. Convert llvm-config shell queries to simply expanded variables (:=) to ensure Make evaluates LLVM compiler flags and library paths exactly once when Makefile.config is parsed, eliminating ~185 redundant sub-processes during build startup. Assisted-by: Gemini:gemini-3.1-pro-preview Signed-off-by: Ian Rogers --- tools/perf/Makefile.config | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config index fbe7fa83b0bb..7a61da082c0b 100644 --- a/tools/perf/Makefile.config +++ b/tools/perf/Makefile.config @@ -951,11 +951,14 @@ ifndef NO_LIBLLVM $(call feature_check,llvm-perf) ifeq ($(feature-llvm-perf), 1) CFLAGS += -DHAVE_LIBLLVM_SUPPORT - CFLAGS += $(shell $(LLVM_CONFIG) --cflags) - CXXFLAGS += -DHAVE_LIBLLVM_SUPPORT - CXXFLAGS += $(shell $(LLVM_CONFIG) --cxxflags) - LIBLLVM = $(shell $(LLVM_CONFIG) --libs all) $(shell $(LLVM_CONFIG) --system-libs) - EXTLIBS += -L$(shell $(LLVM_CONFIG) --libdir) $(LIBLLVM) + LLVM_CFLAGS := $(shell $(LLVM_CONFIG) --cflags 2>/dev/null) + LLVM_CXXFLAGS := $(shell $(LLVM_CONFIG) --cxxflags 2>/dev/null) + LLVM_LIBLLVM := $(shell $(LLVM_CONFIG) --libs all 2>/dev/null) $(shell $(LLVM_CONFIG) --system-libs 2>/dev/null) + LLVM_LIBDIR := $(shell $(LLVM_CONFIG) --libdir 2>/dev/null) + CFLAGS += $(LLVM_CFLAGS) + CXXFLAGS += -DHAVE_LIBLLVM_SUPPORT $(LLVM_CXXFLAGS) + LIBLLVM := $(LLVM_LIBLLVM) + EXTLIBS += -L$(LLVM_LIBDIR) $(LIBLLVM) EXTLIBS += -lstdc++ $(call detected,CONFIG_LIBLLVM) else -- 2.54.0.563.g4f69b47b94-goog