https://bugs.llvm.org/show_bug.cgi?id=38062
Bug ID: 38062
Summary: Using -exhaustive-register-search may lead to assert
(RAGreedy)
Product: new-bugs
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: new bugs
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
When using the option -exhaustive-register-search and a low (or default) value
of -lcr-max-interf you may get the assertion `(i == Size || Traits::stopLess(b,
start(i))) && "Overlapping insert".
This is due to RAGreedy::mayRecolorAllInterferences:
if (Q.collectInterferingVRegs(LastChanceRecoloringMaxInterference) >=
LastChanceRecoloringMaxInterference && !ExhaustiveSearch) {
DEBUG(dbgs() << "Early abort: too many interferences.\n");
CutOffInfo |= CO_Interf;
return false;
}
for (unsigned i = Q.interferingVRegs().size(); i; --i) {
...
If ExhaustiveSearch is set then we loop through the interfering registers to
recolour them. But if LastChanceRecoloringMaxInterference is set to a number
lower than the actual number of interferences then we only process (deallocate)
a subset. When we then allocate the original interval we have introduced an
illegal overlap.
I feel -exhaustive-register-search should imply -lcr-max-interf=inf or at least
print a useful error message. I'm guessing without assertions enabled this
might just lead to wrong codegen.
I'm afraid my target is custom, so I can't provide a test case.
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