On Mon, Apr 24, 2017 at 11:07 PM, Martin Sebor <mse...@gmail.com> wrote: > On 04/24/2017 01:32 AM, Richard Biener wrote: >> >> On Sat, Apr 22, 2017 at 2:51 AM, Martin Sebor <mse...@gmail.com> wrote: >>> >>> Bug 80486 - spurious -Walloc-size-larger-than and >>> -Wstringop-overflow in dominance.c during profiledbootstrap >>> points out a number of warnings that show up in dominance.c >>> during a profiledbootstrap. I'm pretty sure the warnings >>> are due to the size check the C++ new expression introduces >>> to avoid unsigned overflow before calling operator new, and >>> by some optimization like jump threading introducing a branch >>> with the call to the allocation function and memset with >>> the excessive constant size. >>> >>> Two ways to avoid it come to mind: 1) use the libiberty >>> XCNEWVEC and XNEWVEC macros instead of C++ new expressions, >>> and 2) constraining the size variable to a valid range. >>> >>> Either of these approaches should result in better code than >>> the new expression because they both eliminate the test for >>> the overflow. Attached is a patch that implements (1). I >>> chose it mainly because it seems in line with GCC's memory >>> management policy and with avoiding exceptions. >>> >>> An alternate patch should be straightforward. Either add >>> an assert like the one below or change the type of >>> m_n_basic_blocks from size_t to unsigned. This approach, >>> though less intrusive, will likely bring the warning back >>> in ILP32 builds; I'm not sure if it matters. >> >> >> Please change m_n_basic_blocks (and local copies) from size_t >> to unsigned int. This is an odd inconsistency that's worth fixing >> in any case. > > > Attached is this version of the patch. It also eliminates > the warnings and passes profiledbootstrap/regression test > on x86_64.
Ok. Thanks, Richard. > Martin >
