From 773c3b3600d7684351df02ea91d45f18db2c0db1 Mon Sep 17 00:00:00 2001 From: Duncan Sands Date: Fri, 2 Jan 2009 15:16:38 +0000 Subject: Load tracking means that the value analyzed may not have pointer type. In particular, it may be the condition argument for a select or a GEP index. While I was unable to construct a testcase for which some bits of the original pointer are captured due to one of these, it's very very close to being possible - so play safe and exclude these possibilities. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@61580 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/IPO/FunctionAttrs.cpp | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) (limited to 'lib/Transforms') diff --git a/lib/Transforms/IPO/FunctionAttrs.cpp b/lib/Transforms/IPO/FunctionAttrs.cpp index 13fb756..aea4cb4 100644 --- a/lib/Transforms/IPO/FunctionAttrs.cpp +++ b/lib/Transforms/IPO/FunctionAttrs.cpp @@ -198,6 +198,7 @@ bool FunctionAttrs::isCaptured(Function &F, Value *V) { UseWithDepth UD = Worklist.pop_back_val(); Use *U = UD.getPointer(); Instruction *I = cast(U->getUser()); + // The value V may have any type if it comes from tracking a load. V = U->get(); // The depth represents the number of loads that need to be performed to // get back the original pointer (or a bitcast etc of it). For example, @@ -253,7 +254,10 @@ bool FunctionAttrs::isCaptured(Function &F, Value *V) { // Only passed via 'nocapture' arguments, or is the called function - not // captured. } else if (isa(I) || isa(I) || isa(I) || - isa(I) || isa(I)) { + // Play safe and exclude GEP indices. + (isa(I) && V == I->getOperand(0)) || + // Play safe and exclude the select condition. + (isa(I) && V != I->getOperand(0))) { // Usually loads can be ignored because they dereference the original // pointer. However the loaded value needs to be tracked if loading @@ -267,7 +271,9 @@ bool FunctionAttrs::isCaptured(Function &F, Value *V) { continue; // Loading a pointer to (a pointer to...) the original pointer or a // variation of it. Track uses of the loaded value, noting that one - // dereference was performed. + // dereference was performed. Note that the loaded value need not be + // of pointer type. For example, an alloca may have been bitcast to + // a pointer to another type, which was then loaded. --Depth; } -- cgit v1.1