sdisel lowers this to really bad code #1297
Description
| Bugzilla Link | 925 |
| Resolution | FIXED |
| Resolved on | Feb 22, 2010 12:50 |
| Version | 1.8 |
| OS | All |
Extended Description
In the stupid contrived testcase below, sdisel is breaking every critical edge from the switch to the
blahaha block, creating a ton of duplicated code and making switch lowering uglier than it should be.
void foo(int C) {
const char *s = "blah";
switch (C) {
case 1 ... 10:
s = "bonk";
goto blahaha;
}
s = "bork";
if (C & 123) s = "perfwap";
blahaha:
printf(s);
printf(s);
printf(s);
printf(s);
printf(s);
printf(s);
printf(s);
printf(s);
printf(s);
printf(s);
printf(s);
printf(s);
printf(s);
}
We end up with code like this:
LBB1_1: #entry.blahaha_crit_edge9
movl $_str1, %esi
jmp LBB1_14 #blahaha
LBB1_2: #entry.blahaha_crit_edge8
movl $_str1, %esi
jmp LBB1_14 #blahaha
LBB1_3: #entry.blahaha_crit_edge7
movl $_str1, %esi
jmp LBB1_14 #blahaha
LBB1_4: #entry.blahaha_crit_edge6
movl $_str1, %esi
jmp LBB1_14 #blahaha
LBB1_5: #entry.blahaha_crit_edge5
movl $_str1, %esi
jmp LBB1_14 #blahaha
...
When splitting critical edges into a block, SDIsel should factor all edges from a particular BB into a
single split block.
-Chris