linux-kernel - [PATCH v1 1/2] perf report: Check for fused instruction pair

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Date:   Wed, 14 Jun 2017 10:53:40 +0800
From:   Jin Yao <yao.jin@...ux.intel.com>
To:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
        mingo@...hat.com, alexander.shishkin@...ux.intel.com
Cc:     Linux-kernel@...r.kernel.org, ak@...ux.intel.com,
        kan.liang@...el.com, yao.jin@...el.com,
        Jin Yao <yao.jin@...ux.intel.com>
Subject: [PATCH v1 1/2] perf report: Check for fused instruction pair

Macro fusion merges two instructions to a single micro-op. Intel
core platform performs this hardware optimization under limited
circumstances. For example, CMP + JCC can be "fused" and executed
/retired together. While with sampling this can result in the
sample sometimes being on the JCC and sometimes on the CMP.
So for the fused instruction pair, they could be considered
together.

In general, the fused instruction pairs are:

cmp/test/add/sub/and/inc/dec + jcc.

This patch adds a new function which checks if 2 x86 instructions
are in a "fused" pair. For non-x86 arch, the function just returns
false.

Signed-off-by: Jin Yao <yao.jin@...ux.intel.com>
---
 tools/perf/arch/x86/util/Build   |  1 +
 tools/perf/arch/x86/util/fused.c | 20 ++++++++++++++++++++
 tools/perf/util/Build            |  1 +
 tools/perf/util/fused.c          | 11 +++++++++++
 tools/perf/util/fused.h          |  8 ++++++++
 5 files changed, 41 insertions(+)
 create mode 100644 tools/perf/arch/x86/util/fused.c
 create mode 100644 tools/perf/util/fused.c
 create mode 100644 tools/perf/util/fused.h

diff --git a/tools/perf/arch/x86/util/Build b/tools/perf/arch/x86/util/Build
index f95e6f4..3809348 100644
--- a/tools/perf/arch/x86/util/Build
+++ b/tools/perf/arch/x86/util/Build
@@ -4,6 +4,7 @@ libperf-y += pmu.o
 libperf-y += kvm-stat.o
 libperf-y += perf_regs.o
 libperf-y += group.o
+libperf-y += fused.o
 
 libperf-$(CONFIG_DWARF) += dwarf-regs.o
 libperf-$(CONFIG_BPF_PROLOGUE) += dwarf-regs.o
diff --git a/tools/perf/arch/x86/util/fused.c b/tools/perf/arch/x86/util/fused.c
new file mode 100644
index 0000000..be28d22
--- /dev/null
+++ b/tools/perf/arch/x86/util/fused.c
@@ -0,0 +1,20 @@
+#include <string.h>
+#include "../../util/fused.h"
+
+bool fused_insn_pair(const char *insn1, const char *insn2)
+{
+	if (strstr(insn2, "jmp"))
+		return false;
+
+	if ((strstr(insn1, "cmp") && !strstr(insn1, "xchg")) ||
+	    strstr(insn1, "test") ||
+	    strstr(insn1, "add") ||
+	    strstr(insn1, "sub") ||
+	    strstr(insn1, "and") ||
+	    strstr(insn1, "inc") ||
+	    strstr(insn1, "dec")) {
+		return true;
+	}
+
+	return false;
+}
diff --git a/tools/perf/util/Build b/tools/perf/util/Build
index 79dea95..b83757d 100644
--- a/tools/perf/util/Build
+++ b/tools/perf/util/Build
@@ -93,6 +93,7 @@ libperf-y += drv_configs.o
 libperf-y += units.o
 libperf-y += time-utils.o
 libperf-y += expr-bison.o
+libperf-y += fused.o
 
 libperf-$(CONFIG_LIBBPF) += bpf-loader.o
 libperf-$(CONFIG_BPF_PROLOGUE) += bpf-prologue.o
diff --git a/tools/perf/util/fused.c b/tools/perf/util/fused.c
new file mode 100644
index 0000000..2cf56fa
--- /dev/null
+++ b/tools/perf/util/fused.c
@@ -0,0 +1,11 @@
+#include <linux/compiler.h>
+#include <linux/types.h>
+#include <string.h>
+
+#include "fused.h"
+
+bool __weak fused_insn_pair(const char *insn1 __maybe_unused,
+			    const char *insn2 __maybe_unused)
+{
+	return false;
+}
diff --git a/tools/perf/util/fused.h b/tools/perf/util/fused.h
new file mode 100644
index 0000000..fa26714
--- /dev/null
+++ b/tools/perf/util/fused.h
@@ -0,0 +1,8 @@
+#ifndef __PERF_FUSED_H
+#define __PERF_FUSED_H
+
+#include <linux/types.h>
+
+bool fused_insn_pair(const char *insn1, const char *insn2);
+
+#endif	/* __PERF_FUSED_H */
-- 
2.7.4