When a callchain entry has no srcline available, we ended up
comparing the instruction pointer. I consider this to be not
too useful. Rather, I think we should group the entries by
function name, which this patch adds. For people who want to
split the data on the IP boundary, using `-g address` is the
correct choice.

Before:

~~~~~
   100.00%    38.86%  [.] main
            |
            |--61.14%--main inlining.cpp:14
            |          std::norm<double> complex:664
            |          std::_Norm_helper<true>::_S_do_it<double> complex:654
            |          std::abs<double> complex:597
            |          std::__complex_abs complex:589
            |          |
            |          |--56.03%--hypot
            |          |          |
            |          |          |--8.45%--__hypot_finite
            |          |          |
            |          |          |--7.62%--__hypot_finite
            |          |          |
            |          |          |--2.29%--__hypot_finite
            |          |          |
            |          |          |--2.24%--__hypot_finite
            |          |          |
            |          |          |--2.06%--__hypot_finite
            |          |          |
            |          |          |--1.81%--__hypot_finite
...
~~~~~

After:

~~~~~
   100.00%    38.86%  [.] main
            |
            |--61.14%--main inlining.cpp:14
            |          std::norm<double> complex:664
            |          std::_Norm_helper<true>::_S_do_it<double> complex:654
            |          std::abs<double> complex:597
            |          std::__complex_abs complex:589
            |          |
            |          |--60.29%--hypot
            |          |          |
            |          |           --56.03%--__hypot_finite
            |          |
            |           --0.85%--cabs
~~~~~

Cc: Arnaldo Carvalho de Melo <a...@redhat.com>
Cc: David Ahern <dsah...@gmail.com>
Cc: Namhyung Kim <namhy...@kernel.org>
Cc: Peter Zijlstra <a.p.zijls...@chello.nl>
Cc: Yao Jin <yao....@linux.intel.com>
Signed-off-by: Milian Wolff <milian.wo...@kdab.com>
---
 tools/perf/util/callchain.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/tools/perf/util/callchain.c b/tools/perf/util/callchain.c
index 9854adb06ac1..6afa8ccd75b5 100644
--- a/tools/perf/util/callchain.c
+++ b/tools/perf/util/callchain.c
@@ -638,11 +638,9 @@ enum match_result {
        MATCH_GT,
 };
 
-static enum match_result match_chain_srcline(struct callchain_cursor_node 
*node,
-                                            struct callchain_list *cnode)
+static enum match_result match_chain_strings(const char *left,
+                                            const char *right)
 {
-       const char *left = cnode->srcline;
-       const char *right = node->srcline;
        enum match_result ret = MATCH_EQ;
        int cmp;
 
@@ -652,10 +650,8 @@ static enum match_result match_chain_srcline(struct 
callchain_cursor_node *node,
                cmp = 1;
        else if (left && !right)
                cmp = -1;
-       else if (cnode->ip == node->ip)
-               cmp = 0;
        else
-               cmp = (cnode->ip < node->ip) ? -1 : 1;
+               return MATCH_ERROR;
 
        if (cmp != 0)
                ret = cmp < 0 ? MATCH_LT : MATCH_GT;
@@ -670,10 +666,18 @@ static enum match_result match_chain(struct 
callchain_cursor_node *node,
        u64 left, right;
 
        if (callchain_param.key == CCKEY_SRCLINE) {
-               enum match_result match = match_chain_srcline(node, cnode);
+               enum match_result match = match_chain_strings(cnode->srcline,
+                                                             node->srcline);
+
+               // if no srcline is available, fallback to symbol name
+               if (match == MATCH_ERROR && cnode->ms.sym && node->sym)
+                       match = match_chain_strings(cnode->ms.sym->name,
+                                                   node->sym->name);
 
                if (match != MATCH_ERROR)
                        return match;
+
+               // otherwise fall-back to IP-based comparison below
        }
 
        if (cnode->ms.sym && sym && callchain_param.key == CCKEY_FUNCTION) {
-- 
2.13.3

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