https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88763
--- Comment #11 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Thanks for the testcase.
(In reply to David Malcolm from comment #10)
> Created attachment 45406 [details]
> Followup patch to try to dump why a condition can't be unswitched within a
> loop
This is a followup patch (on top of the one in comment #6), which tries to dump
the desired information from comment #7.
On the testcase from comment #9, it gives:
$ ./xgcc -B. -c /tmp/t.c -O2 -funswitch-loops -fopt-info-loop-all
/tmp/t.c:17:9: missed: within this loop...
/tmp/t.c:5:7: missed: ...cannot unswitch condition: if (_16 > 5)
/tmp/t.c:3:11: missed: ...as condition is not invariant within loop; modified
here by: _16 = flag_37 + 2;
/tmp/t.c:17:9: missed: within this loop...
/tmp/t.c:17:9: missed: ...cannot unswitch condition: if (j_11 != 250)
/tmp/t.c:17:34: missed: ...as condition is not invariant within loop; modified
here by: j_11 = j_34 + 1;
i.e. it's emitting 3 messages per unswitchable condition, highlighting each of:
* the loop
* the condition
* the problematic statement
The -fsave-optimization-record version of this dump also captures the function
name (and the inlining chain, for inlined statements, such as that of the
condition within the "calc" inlined within "main"):
{
"count": {
"quality": "guessed_local",
"value": 1063000000.0
},
"function": "main",
"impl_location": {
"file": "../../src/gcc/tree-ssa-loop-unswitch.c",
"function": "dump_unswitchable_condition",
"line": 198
},
"inlining_chain": [
{
"fndecl": "calc"
},
{
"fndecl": "main",
"site": {
"column": 25,
"file": "/tmp/t.c",
"line": 19
}
}
],
"kind": "failure",
"location": {
"column": 7,
"file": "/tmp/t.c",
"line": 5
},
"message": [
"...cannot unswitch condition: ",
{
"location": {
"column": 7,
"file": "/tmp/t.c",
"line": 5
},
"stmt": "if (_16 > 5)\n"
}
],
"pass": "0x3a33250"
},
How does this look?
FWIW, this is feeling like gcc 10 material.
