forked from OSchip/llvm-project
f02b8bf11b
The partitioning logic attempted to handle uses of an alloca with an offset starting before the alloca so long as the use had some overlap with the alloca itself. However, there was a bug where we tested '(uint64_t)Offset >= AllocSize' without first checking whether 'Offset' was positive. As a consequence, essentially every negative offset (that is, starting *before* the alloca does) would be thrown out, even if it was overlapping. The subsequent code to throw out negative offsets which were actually non-overlapping was essentially dead. The code to *handle* overlapping negative offsets was actually dead! I've just removed all of this, and taught SROA to discard any uses which start prior to the alloca from the beginning. It has the lovely property of simplifying the code. =] All the tests still pass, and in fact no new tests are needed as this is already covered by our testsuite. Fixing the code so that negative offsets work the way the comments indicate they were supposed to work causes regressions. That's how I found this. Anyways, this is all progress in the correct direction -- tightening up SROA to be maximally aggressive. Some day, I really hope to turn out-of-bounds accesses to an alloca into 'unreachable'. llvm-svn: 169120 |
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README.txt
Low Level Virtual Machine (LLVM) ================================ This directory and its subdirectories contain source code for the Low Level Virtual Machine, a toolkit for the construction of highly optimized compilers, optimizers, and runtime environments. LLVM is open source software. You may freely distribute it under the terms of the license agreement found in LICENSE.txt. Please see the HTML documentation provided in docs/index.html for further assistance with LLVM. If you're writing a package for LLVM, see docs/Packaging.html for our suggestions.