perf annotate browser: Initial loop detection

Simple algorithm, just look for the next backward jump that points to
before the cursor.

Then draw an arrow connecting the jump to its target.

Do this as you move the cursor, entering/exiting possible loops.

Ex (graph chars replaced to avoid mail encoding woes):

avc_has_perm_flags
    0.00 |         nopl   0x0(%rax)
    5.36 |+-> 68:  mov    (%rax),%rax
    5.15 ||        test   %rax,%rax
    0.00 ||      v je     130
    2.96 ||   74:  cmp    -0x20(%rax),%ebx
   47.38 ||        lea    -0x20(%rax),%rcx
    0.28 ||      ^ jne    68
    3.16 ||        cmp    -0x18(%rax),%dx
    0.00 |+------^ jne    68
    4.92 |         cmp    0x4(%rcx),%r13d
    0.00 |       v jne    68
    1.15 |         test   %rcx,%rcx
    0.00 |       v je     130

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-5gairf6or7dazlx3ocxwvftm@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 39 insertions, 0 deletions

diff --git a/tools/perf/ui/browser.c b/tools/perf/ui/browser.c
index 973ff74e3640..32ac1165100d 100644
--- a/tools/perf/ui/browser.c
+++ b/tools/perf/ui/browser.c
@@ -600,6 +600,45 @@ void ui_browser__write_graph(struct ui_browser *browser __used, int graph)
 	SLsmg_set_char_set(0);
 }
 
+void __ui_browser__line_arrow_up(struct ui_browser *browser, unsigned int column,
+				 u64 start, u64 end, int start_width)
+{
+	unsigned int row, end_row;
+
+	SLsmg_set_char_set(1);
+
+	if (start < browser->top_idx + browser->height) {
+		row = start - browser->top_idx;
+		ui_browser__gotorc(browser, row, column);
+		SLsmg_write_char(SLSMG_LLCORN_CHAR);
+		ui_browser__gotorc(browser, row, column + 1);
+		SLsmg_draw_hline(start_width);
+
+		if (row-- == 0)
+			goto out;
+	} else
+		row = browser->height - 1;
+
+	if (end > browser->top_idx)
+		end_row = end - browser->top_idx;
+	else
+		end_row = 0;
+
+	ui_browser__gotorc(browser, end_row, column);
+	SLsmg_draw_vline(row - end_row + 1);
+
+	ui_browser__gotorc(browser, end_row, column);
+	if (end >= browser->top_idx) {
+		SLsmg_write_char(SLSMG_ULCORN_CHAR);
+		ui_browser__gotorc(browser, end_row, column + 1);
+		SLsmg_write_char(SLSMG_HLINE_CHAR);
+		ui_browser__gotorc(browser, end_row, column + 2);
+		SLsmg_write_char(SLSMG_RARROW_CHAR);
+	}
+out:
+	SLsmg_set_char_set(0);
+}
+
 void ui_browser__init(void)
 {
 	int i = 0;