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Date: Sat, 11 Sep 2021 16:03:57 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Jin Yao <yao.jin@...ux.intel.com>,
Ravi Bangoria <ravi.bangoria@....com>
Cc: mark.rutland@....com, alexander.shishkin@...ux.intel.com,
jolsa@...hat.com, namhyung@...nel.org, kim.phillips@....com,
linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] perf annotate: Fix fused instr logic for assembly
functions
Em Sat, Sep 11, 2021 at 10:08:53AM +0530, Ravi Bangoria escreveu:
> Some x86 microarchitectures fuse a subset of cmp/test/ALU instructions
> with branch instructions, and thus perf annotate highlight such valid
> pairs as fused.
Jin, are you ok with this? Can I have your reviewed-by?
- Arnaldo
> When annotated with source, perf uses struct disasm_line to contain
> either source or instruction line from objdump output. Usually, a C
> statement generates multiple instructions which include such
> cmp/test/ALU + branch instruction pairs. But in case of assembly
> function, each individual assembly source line generate one
> instruction. Perf annotate instruction fusion logic assumes previous
> disasm_line as previous instruction line, which is wrong because,
> for assembly function, previous disasm_line contains source line.
> And thus perf fails to highlight valid fused instruction pairs for
> assembly functions.
>
> Fix it by searching backward until we find an instruction line and
> consider that disasm_line as fused with current branch instruction.
>
> Before:
> │ cmpq %rcx, RIP+8(%rsp)
> 0.00 │ cmp %rcx,0x88(%rsp)
> │ je .Lerror_bad_iret <--- Source line
> 0.14 │ ┌──je b4 <--- Instruction line
> │ │movl %ecx, %eax
>
> After:
> │ cmpq %rcx, RIP+8(%rsp)
> 0.00 │ ┌──cmp %rcx,0x88(%rsp)
> │ │je .Lerror_bad_iret
> 0.14 │ ├──je b4
> │ │movl %ecx, %eax
>
> Signed-off-by: Ravi Bangoria <ravi.bangoria@....com>
> ---
> tools/perf/ui/browser.c | 33 ++++++++++++++++++++++---------
> tools/perf/ui/browser.h | 2 +-
> tools/perf/ui/browsers/annotate.c | 24 +++++++++++++++-------
> 3 files changed, 42 insertions(+), 17 deletions(-)
>
> diff --git a/tools/perf/ui/browser.c b/tools/perf/ui/browser.c
> index 781afe42e90e..fa5bd5c20e96 100644
> --- a/tools/perf/ui/browser.c
> +++ b/tools/perf/ui/browser.c
> @@ -757,25 +757,40 @@ void __ui_browser__line_arrow(struct ui_browser *browser, unsigned int column,
> }
>
> void ui_browser__mark_fused(struct ui_browser *browser, unsigned int column,
> - unsigned int row, bool arrow_down)
> + unsigned int row, int diff, bool arrow_down)
> {
> - unsigned int end_row;
> + int end_row;
>
> - if (row >= browser->top_idx)
> - end_row = row - browser->top_idx;
> - else
> + if (diff <= 0)
> return;
>
> SLsmg_set_char_set(1);
>
> if (arrow_down) {
> + if (row + diff <= browser->top_idx)
> + return;
> +
> + end_row = row + diff - browser->top_idx;
> ui_browser__gotorc(browser, end_row, column - 1);
> - SLsmg_write_char(SLSMG_ULCORN_CHAR);
> - ui_browser__gotorc(browser, end_row, column);
> - SLsmg_draw_hline(2);
> - ui_browser__gotorc(browser, end_row + 1, column - 1);
> SLsmg_write_char(SLSMG_LTEE_CHAR);
> +
> + while (--end_row >= 0 && end_row > (int)(row - browser->top_idx)) {
> + ui_browser__gotorc(browser, end_row, column - 1);
> + SLsmg_draw_vline(1);
> + }
> +
> + end_row = (int)(row - browser->top_idx);
> + if (end_row >= 0) {
> + ui_browser__gotorc(browser, end_row, column - 1);
> + SLsmg_write_char(SLSMG_ULCORN_CHAR);
> + ui_browser__gotorc(browser, end_row, column);
> + SLsmg_draw_hline(2);
> + }
> } else {
> + if (row < browser->top_idx)
> + return;
> +
> + end_row = row - browser->top_idx;
> ui_browser__gotorc(browser, end_row, column - 1);
> SLsmg_write_char(SLSMG_LTEE_CHAR);
> ui_browser__gotorc(browser, end_row, column);
> diff --git a/tools/perf/ui/browser.h b/tools/perf/ui/browser.h
> index 3678eb88f119..510ce4554050 100644
> --- a/tools/perf/ui/browser.h
> +++ b/tools/perf/ui/browser.h
> @@ -51,7 +51,7 @@ void ui_browser__write_graph(struct ui_browser *browser, int graph);
> void __ui_browser__line_arrow(struct ui_browser *browser, unsigned int column,
> u64 start, u64 end);
> void ui_browser__mark_fused(struct ui_browser *browser, unsigned int column,
> - unsigned int row, bool arrow_down);
> + unsigned int row, int diff, bool arrow_down);
> void __ui_browser__show_title(struct ui_browser *browser, const char *title);
> void ui_browser__show_title(struct ui_browser *browser, const char *title);
> int ui_browser__show(struct ui_browser *browser, const char *title,
> diff --git a/tools/perf/ui/browsers/annotate.c b/tools/perf/ui/browsers/annotate.c
> index ef4da4295bf7..e81c2493efdf 100644
> --- a/tools/perf/ui/browsers/annotate.c
> +++ b/tools/perf/ui/browsers/annotate.c
> @@ -125,13 +125,20 @@ static void annotate_browser__write(struct ui_browser *browser, void *entry, int
> ab->selection = al;
> }
>
> -static bool is_fused(struct annotate_browser *ab, struct disasm_line *cursor)
> +static int is_fused(struct annotate_browser *ab, struct disasm_line *cursor)
> {
> struct disasm_line *pos = list_prev_entry(cursor, al.node);
> const char *name;
> + int diff = 1;
> +
> + while (pos && pos->al.offset == -1) {
> + pos = list_prev_entry(pos, al.node);
> + if (!ab->opts->hide_src_code)
> + diff++;
> + }
>
> if (!pos)
> - return false;
> + return 0;
>
> if (ins__is_lock(&pos->ins))
> name = pos->ops.locked.ins.name;
> @@ -139,9 +146,11 @@ static bool is_fused(struct annotate_browser *ab, struct disasm_line *cursor)
> name = pos->ins.name;
>
> if (!name || !cursor->ins.name)
> - return false;
> + return 0;
>
> - return ins__is_fused(ab->arch, name, cursor->ins.name);
> + if (ins__is_fused(ab->arch, name, cursor->ins.name))
> + return diff;
> + return 0;
> }
>
> static void annotate_browser__draw_current_jump(struct ui_browser *browser)
> @@ -155,6 +164,7 @@ static void annotate_browser__draw_current_jump(struct ui_browser *browser)
> struct annotation *notes = symbol__annotation(sym);
> u8 pcnt_width = annotation__pcnt_width(notes);
> int width;
> + int diff = 0;
>
> /* PLT symbols contain external offsets */
> if (strstr(sym->name, "@plt"))
> @@ -205,11 +215,11 @@ static void annotate_browser__draw_current_jump(struct ui_browser *browser)
> pcnt_width + 2 + notes->widths.addr + width,
> from, to);
>
> - if (is_fused(ab, cursor)) {
> + diff = is_fused(ab, cursor);
> + if (diff > 0) {
> ui_browser__mark_fused(browser,
> pcnt_width + 3 + notes->widths.addr + width,
> - from - 1,
> - to > from);
> + from - diff, diff, to > from);
> }
> }
>
> --
> 2.27.0
--
- Arnaldo
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