From: Markus Metzger Date: Tue, 12 Jan 2016 15:05:15 +0000 (+0100) Subject: btrace: update tail call heuristic X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=2dfdb47abd418aac05380482093a87e763ab0a05;p=binutils-gdb.git btrace: update tail call heuristic An unconditional jump to the start of a function typically indicates a tail call. If we can't determine the start of the function at the destination address, we used to treat it as a tail call, as well. This results in lots of tail calls for code for which we don't have symbol information. Restrict the heuristic to only consider jumps as tail calls that switch functions in the case where we can't determine the start of a function. This effectively disables tail call detection for code without symbol information. gdb/ * btrace.c (ftrace_update_function): Update tail call heuristic. --- diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 350e5a627dd..98e13ea9b60 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,7 @@ +2016-10-28 Markus Metzger + + * btrace.c (ftrace_update_function): Update tail call heuristic. + 2016-10-28 Markus Metzger * btrace.c (btrace_compute_ftrace_bts, ftrace_add_pt): Allow diff --git a/gdb/btrace.c b/gdb/btrace.c index 648d49532bb..445f0a4c165 100644 --- a/gdb/btrace.c +++ b/gdb/btrace.c @@ -529,10 +529,17 @@ ftrace_update_function (struct btrace_function *bfun, CORE_ADDR pc) start = get_pc_function_start (pc); + /* A jump to the start of a function is (typically) a tail call. */ + if (start == pc) + return ftrace_new_tailcall (bfun, mfun, fun); + /* If we can't determine the function for PC, we treat a jump at - the end of the block as tail call. */ - if (start == 0 || start == pc) + the end of the block as tail call if we're switching functions + and as an intra-function branch if we don't. */ + if (start == 0 && ftrace_function_switched (bfun, mfun, fun)) return ftrace_new_tailcall (bfun, mfun, fun); + + break; } } }