From 4d63c8daec1759e60f85a49b7a91f88edf0c0a4d Mon Sep 17 00:00:00 2001 From: Benjamin Kramer Date: Thu, 3 Oct 2013 13:24:02 +0000 Subject: [PATCH] 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 --- lib/Analysis/CaptureTracking.cpp | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/lib/Analysis/CaptureTracking.cpp b/lib/Analysis/CaptureTracking.cpp index 9eb76a8b27b..79fab1be441 100644 --- a/lib/Analysis/CaptureTracking.cpp +++ b/lib/Analysis/CaptureTracking.cpp @@ -146,8 +146,14 @@ void llvm::PointerMayBeCaptured(const Value *V, CaptureTracker *Tracker) { 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))