linux-kernel - [PATCH v7 02/11] perf llvm: Reduce LLVM initialization

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Message-ID: <20251005212212.2892175-3-irogers@google.com>
Date: Sun,  5 Oct 2025 14:22:03 -0700
From: Ian Rogers <irogers@...gle.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>, Peter Zijlstra <peterz@...radead.org>, 
	Ingo Molnar <mingo@...hat.com>, Namhyung Kim <namhyung@...nel.org>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Nathan Chancellor <nathan@...nel.org>, Nick Desaulniers <nick.desaulniers+lkml@...il.com>, 
	Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>, 
	Charlie Jenkins <charlie@...osinc.com>, Eric Biggers <ebiggers@...nel.org>, 
	"Masami Hiramatsu (Google)" <mhiramat@...nel.org>, James Clark <james.clark@...aro.org>, 
	Collin Funk <collin.funk1@...il.com>, "Dr. David Alan Gilbert" <linux@...blig.org>, 
	Li Huafei <lihuafei1@...wei.com>, Athira Rajeev <atrajeev@...ux.ibm.com>, 
	Stephen Brennan <stephen.s.brennan@...cle.com>, Dmitry Vyukov <dvyukov@...gle.com>, 
	Alexandre Ghiti <alexghiti@...osinc.com>, Haibo Xu <haibo1.xu@...el.com>, 
	Andi Kleen <ak@...ux.intel.com>, linux-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org, bpf@...r.kernel.org, llvm@...ts.linux.dev, 
	Song Liu <song@...nel.org>
Subject: [PATCH v7 02/11] perf llvm: Reduce LLVM initialization

Move the 3 LLVM initialization routines to be called in a single
init_llvm function that has its own bool to avoid repeated
initialization. Reduce the scope of triplet and avoid copying strings
for x86.

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/util/llvm.c | 31 ++++++++++++++++++++-----------
 1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/tools/perf/util/llvm.c b/tools/perf/util/llvm.c
index ddc737194692..2356778955fe 100644
--- a/tools/perf/util/llvm.c
+++ b/tools/perf/util/llvm.c
@@ -74,6 +74,17 @@ void dso__free_a2l_llvm(struct dso *dso __maybe_unused)
 	/* Nothing to free. */
 }
 
+static void init_llvm(void)
+{
+	static bool init;
+
+	if (!init) {
+		LLVMInitializeAllTargetInfos();
+		LLVMInitializeAllTargetMCs();
+		LLVMInitializeAllDisassemblers();
+		init = true;
+	}
+}
 
 #if defined(HAVE_LIBLLVM_SUPPORT)
 struct find_file_offset_data {
@@ -184,7 +195,6 @@ int symbol__disassemble_llvm(const char *filename, struct symbol *sym,
 	u64 len;
 	u64 pc;
 	bool is_64bit;
-	char triplet[64];
 	char disasm_buf[2048];
 	size_t disasm_len;
 	struct disasm_line *dl;
@@ -197,26 +207,25 @@ int symbol__disassemble_llvm(const char *filename, struct symbol *sym,
 	if (args->options->objdump_path)
 		return -1;
 
-	LLVMInitializeAllTargetInfos();
-	LLVMInitializeAllTargetMCs();
-	LLVMInitializeAllDisassemblers();
-
 	buf = read_symbol(filename, map, sym, &len, &is_64bit);
 	if (buf == NULL)
 		return -1;
 
+	init_llvm();
 	if (arch__is(args->arch, "x86")) {
-		if (is_64bit)
-			scnprintf(triplet, sizeof(triplet), "x86_64-pc-linux");
-		else
-			scnprintf(triplet, sizeof(triplet), "i686-pc-linux");
+		const char *triplet = is_64bit ? "x86_64-pc-linux" : "i686-pc-linux";
+
+		disasm = LLVMCreateDisasm(triplet, &storage, /*tag_type=*/0,
+					  /*get_op_info=*/NULL, symbol_lookup_callback);
 	} else {
+		char triplet[64];
+
 		scnprintf(triplet, sizeof(triplet), "%s-linux-gnu",
 			  args->arch->name);
+		disasm = LLVMCreateDisasm(triplet, &storage, /*tag_type=*/0,
+					  /*get_op_info=*/NULL, symbol_lookup_callback);
 	}
 
-	disasm = LLVMCreateDisasm(triplet, &storage, 0, NULL,
-				  symbol_lookup_callback);
 	if (disasm == NULL)
 		goto err;
 
-- 
2.51.0.618.g983fd99d29-goog