From 94e617627d06af901a12526a176cbfb67835e6d9 Mon Sep 17 00:00:00 2001 From: Dan Gohman Date: Thu, 19 Nov 2009 21:57:48 +0000 Subject: Extend CaptureTracking to indicate when a value is never stored, even if it is not ultimately captured. Teach BasicAliasAnalysis that a local object address which does not escape and is never stored does not alias with a value resulting from a load. llvm-svn: 89398 --- llvm/lib/Analysis/CaptureTracking.cpp | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) (limited to 'llvm/lib/Analysis/CaptureTracking.cpp') diff --git a/llvm/lib/Analysis/CaptureTracking.cpp b/llvm/lib/Analysis/CaptureTracking.cpp index 7cd055dcd..ae0766b 100644 --- a/llvm/lib/Analysis/CaptureTracking.cpp +++ b/llvm/lib/Analysis/CaptureTracking.cpp @@ -28,8 +28,11 @@ using namespace llvm; /// by the enclosing function (which is required to exist). This routine can /// be expensive, so consider caching the results. The boolean ReturnCaptures /// specifies whether returning the value (or part of it) from the function +/// counts as capturing it or not. The boolean StoreCaptures specified whether +/// storing the value (or part of it) into memory anywhere automatically /// counts as capturing it or not. -bool llvm::PointerMayBeCaptured(const Value *V, bool ReturnCaptures) { +bool llvm::PointerMayBeCaptured(const Value *V, + bool ReturnCaptures, bool StoreCaptures) { assert(isa(V->getType()) && "Capture is for pointers only!"); SmallVector Worklist; SmallSet Visited; @@ -82,7 +85,11 @@ bool llvm::PointerMayBeCaptured(const Value *V, bool ReturnCaptures) { break; case Instruction::Store: if (V == I->getOperand(0)) - // Stored the pointer - it may be captured. + // Stored the pointer - conservatively assume it may be captured. + // TODO: If StoreCaptures is not true, we could do Fancy analysis + // to determine whether this store is not actually an escape point. + // In that case, BasicAliasAnalysis should be updated as well to + // take advantage of this. return true; // Storing to the pointee does not cause the pointer to be captured. break; -- cgit v1.1