CaptureTracking: Plug a loophole in the "too many uses" heuristic.
The heuristic was added to avoid spending too much compile time A specially
crafted test case (PR17461, PR16474) with many uses on a select or bitcast
instruction can still trigger the slow case. Add a check for that case.
This only affects compile time, don't have a good way to test it.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191896 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/CaptureTracking.cpp b/lib/Analysis/CaptureTracking.cpp
index 9eb76a8..79fab1b 100644
--- a/lib/Analysis/CaptureTracking.cpp
+++ b/lib/Analysis/CaptureTracking.cpp
@@ -146,8 +146,14 @@
case Instruction::PHI:
case Instruction::Select:
// The original value is not captured via this if the new value isn't.
+ Count = 0;
for (Instruction::use_iterator UI = I->use_begin(), UE = I->use_end();
UI != UE; ++UI) {
+ // If there are lots of uses, conservatively say that the value
+ // is captured to avoid taking too much compile time.
+ if (Count++ >= Threshold)
+ return Tracker->tooManyUses();
+
Use *U = &UI.getUse();
if (Visited.insert(U))
if (Tracker->shouldExplore(U))