svn commit: r258608 - stable/9/contrib/llvm/lib/Analysis

[Dimitry Andric]

Author: dim
Date: Mon Nov 25 22:58:12 2013
New Revision: 258608
URL: http://svnweb.freebsd.org/changeset/base/258608

Log:
  MFC r258350:
  
  Pull in r191896 from upstream llvm trunk:
  
    CaptureTracking: Plug a loophole in the "too many uses" heuristic.
  
    The heuristic was added to avoid spending too much compile time in 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.
  
  This fixes the excessive compile time spent on a specific file of the
  graphics/rawtherapee port.
  
  Reported by:	mandree

Modified:
  stable/9/contrib/llvm/lib/Analysis/CaptureTracking.cpp
Directory Properties:
  stable/9/contrib/llvm/   (props changed)

Modified: stable/9/contrib/llvm/lib/Analysis/CaptureTracking.cpp
==============================================================================
--- stable/9/contrib/llvm/lib/Analysis/CaptureTracking.cpp	Mon Nov 25 22:56:46 2013	(r258607)
+++ stable/9/contrib/llvm/lib/Analysis/CaptureTracking.cpp	Mon Nov 25 22:58:12 2013	(r258608)
@@ -146,8 +146,14 @@ void llvm::PointerMayBeCaptured(const Va
     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))