linux-kernel - [PATCH 3/4] perf script: Show branch speculation info

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Message-ID: <d56c9d54839b9f114525cc31cc4d9455f1ff6008.1660217326.git.sandipan.das@amd.com>
Date:   Thu, 11 Aug 2022 18:16:48 +0530
From:   Sandipan Das <sandipan.das@....com>
To:     <linux-kernel@...r.kernel.org>, <linux-perf-users@...r.kernel.org>,
        <x86@...nel.org>
CC:     <peterz@...radead.org>, <bp@...en8.de>, <acme@...nel.org>,
        <namhyung@...nel.org>, <jolsa@...nel.org>, <tglx@...utronix.de>,
        <mingo@...hat.com>, <mark.rutland@....com>,
        <alexander.shishkin@...ux.intel.com>,
        <dave.hansen@...ux.intel.com>, <like.xu.linux@...il.com>,
        <eranian@...gle.com>, <ananth.narayan@....com>,
        <ravi.bangoria@....com>, <santosh.shukla@....com>,
        <sandipan.das@....com>
Subject: [PATCH 3/4] perf script: Show branch speculation info

Show the branch speculation info if provided by the branch recording
hardware feature. This can be useful for optimizing code further.

The speculation info is appended to the end of the list of fields so any
existing tools that use "/" as a delimiter for access fields via an index
remain unaffected. Also show "-" instead of "N/A" when speculation info
is unavailable because "/" is used as the field separator.

E.g.

  $ perf record -j any,u,save_type ./test_branch
  $ perf script --fields brstacksym

Before:

  [...]
  check_match+0x60/strcmp+0x0/P/-/-/0/CALL
  do_lookup_x+0x3c5/check_match+0x0/P/-/-/0/CALL
  [...]

After:

  [...]
  check_match+0x60/strcmp+0x0/P/-/-/0/CALL/NON_SPEC_CORRECT_PATH
  do_lookup_x+0x3c5/check_match+0x0/P/-/-/0/CALL/NON_SPEC_CORRECT_PATH
  [...]

Signed-off-by: Sandipan Das <sandipan.das@....com>
---
 tools/perf/builtin-script.c |  5 +++--
 tools/perf/util/branch.c    | 15 +++++++++++++++
 tools/perf/util/branch.h    |  5 ++++-
 tools/perf/util/evsel.c     |  9 ++++++---
 4 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
index ac19fee62d8e..d294ac804244 100644
--- a/tools/perf/builtin-script.c
+++ b/tools/perf/builtin-script.c
@@ -872,12 +872,13 @@ mispred_str(struct branch_entry *br)
 
 static int print_bstack_flags(FILE *fp, struct branch_entry *br)
 {
-	return fprintf(fp, "/%c/%c/%c/%d/%s ",
+	return fprintf(fp, "/%c/%c/%c/%d/%s/%s ",
 		       mispred_str(br),
 		       br->flags.in_tx ? 'X' : '-',
 		       br->flags.abort ? 'A' : '-',
 		       br->flags.cycles,
-		       br->flags.type ? branch_type_name(br->flags.type) : "-");
+		       br->flags.type ? branch_type_name(br->flags.type) : "-",
+		       br->flags.spec ? branch_spec_desc(br->flags.spec) : "-");
 }
 
 static int perf_sample__fprintf_brstack(struct perf_sample *sample,
diff --git a/tools/perf/util/branch.c b/tools/perf/util/branch.c
index a9a909db8cc7..29d89425a011 100644
--- a/tools/perf/util/branch.c
+++ b/tools/perf/util/branch.c
@@ -146,3 +146,18 @@ int branch_type_str(struct branch_type_stat *st, char *bf, int size)
 
 	return printed;
 }
+
+const char *branch_spec_desc(int spec)
+{
+	const char *branch_spec_outcomes[PERF_BR_SPEC_MAX] = {
+		"N/A",
+		"SPEC_WRONG_PATH",
+		"NON_SPEC_CORRECT_PATH",
+		"SPEC_CORRECT_PATH",
+	};
+
+	if (spec >= 0 && spec < PERF_BR_SPEC_MAX)
+		return branch_spec_outcomes[spec];
+
+	return NULL;
+}
diff --git a/tools/perf/util/branch.h b/tools/perf/util/branch.h
index 17b2ccc61094..8563b88b8281 100644
--- a/tools/perf/util/branch.h
+++ b/tools/perf/util/branch.h
@@ -24,7 +24,8 @@ struct branch_flags {
 			u64 abort:1;
 			u64 cycles:16;
 			u64 type:4;
-			u64 reserved:40;
+			u64 spec:2;
+			u64 reserved:38;
 		};
 	};
 };
@@ -85,4 +86,6 @@ const char *branch_type_name(int type);
 void branch_type_stat_display(FILE *fp, struct branch_type_stat *st);
 int branch_type_str(struct branch_type_stat *st, char *bf, int bfsize);
 
+const char *branch_spec_desc(int spec);
+
 #endif /* _PERF_BRANCH_H */
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 4852089e1d79..e47cf16bef0a 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2313,7 +2313,8 @@ u64 evsel__bitfield_swap_branch_flags(u64 value)
 	 * 		abort:1		//transaction abort
 	 * 		cycles:16	//cycle count to last branch
 	 * 		type:4		//branch type
-	 * 		reserved:40
+	 * 		spec:2		//branch speculation info
+	 * 		reserved:38
 	 * 	}
 	 * }
 	 *
@@ -2332,7 +2333,8 @@ u64 evsel__bitfield_swap_branch_flags(u64 value)
 		new_val |= bitfield_swap(value, 3, 1);
 		new_val |= bitfield_swap(value, 4, 16);
 		new_val |= bitfield_swap(value, 20, 4);
-		new_val |= bitfield_swap(value, 24, 40);
+		new_val |= bitfield_swap(value, 24, 2);
+		new_val |= bitfield_swap(value, 26, 38);
 	} else {
 		new_val = bitfield_swap(value, 63, 1);
 		new_val |= bitfield_swap(value, 62, 1);
@@ -2340,7 +2342,8 @@ u64 evsel__bitfield_swap_branch_flags(u64 value)
 		new_val |= bitfield_swap(value, 60, 1);
 		new_val |= bitfield_swap(value, 44, 16);
 		new_val |= bitfield_swap(value, 40, 4);
-		new_val |= bitfield_swap(value, 0, 40);
+		new_val |= bitfield_swap(value, 38, 2);
+		new_val |= bitfield_swap(value, 0, 38);
 	}
 
 	return new_val;
-- 
2.34.1