From 76c638a14c1e2927e5e20040b347bc3d7ae8fb82 Mon Sep 17 00:00:00 2001 From: Dan Gohman Date: Fri, 20 Nov 2009 00:50:47 +0000 Subject: Refine the capture tracking rules for comparisons to be more careful about crazy methods of capturing pointers using comparisons. Comparisons of identified objects with null in the default address space are not captures. And, comparisons of two pointers within the same identified object are not captures. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@89421 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Analysis/CaptureTracking.cpp | 25 +++++++++++++++++++------ 1 file changed, 19 insertions(+), 6 deletions(-) (limited to 'lib/Analysis/CaptureTracking.cpp') diff --git a/lib/Analysis/CaptureTracking.cpp b/lib/Analysis/CaptureTracking.cpp index 9f27e3dd18..e86ad96e4a 100644 --- a/lib/Analysis/CaptureTracking.cpp +++ b/lib/Analysis/CaptureTracking.cpp @@ -19,6 +19,7 @@ #include "llvm/Analysis/CaptureTracking.h" #include "llvm/Instructions.h" #include "llvm/Value.h" +#include "llvm/Analysis/AliasAnalysis.h" #include "llvm/ADT/SmallSet.h" #include "llvm/ADT/SmallVector.h" #include "llvm/Support/CallSite.h" @@ -104,13 +105,25 @@ bool llvm::PointerMayBeCaptured(const Value *V, Worklist.push_back(U); } break; - case Instruction::ICmp: - // Comparing the pointer against null does not count as a capture. - if (ConstantPointerNull *CPN = - dyn_cast(I->getOperand(1))) - if (CPN->getType()->getAddressSpace() == 0) - break; + case Instruction::ICmp: { + // Don't count comparisons of the original value against null as captures. + // This allows us to ignore comparisons of malloc results with null, + // for example. + if (isIdentifiedObject(V)) + if (ConstantPointerNull *CPN = + dyn_cast(I->getOperand(1))) + if (CPN->getType()->getAddressSpace() == 0) + break; + // Don't count comparisons of two pointers within the same identified + // object as captures. + Value *O0 = I->getOperand(0)->getUnderlyingObject(); + if (isIdentifiedObject(O0) && + O0 == I->getOperand(1)->getUnderlyingObject()) + break; + // Otherwise, be conservative. There are crazy ways to capture pointers + // using comparisons. return true; + } default: // Something else - be conservative and say it is captured. return true; -- cgit v1.2.3