[llvm-dev] Possible soundness issue with available_externally (split from "RFC: Add guard intrinsics")

[Duncan P. N. Exon Smith via llvm-dev]

Nice repro.  It looks well-defined to me too.

Is there a PR open yet?

> On 2016-Feb-29, at 08:21, Sanjoy Das via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> 
> On Sat, Feb 27, 2016 at 1:41 PM, Sanjoy Das
> <sanjoy at playingwithpointers.com> wrote:
>> Just as a reality check, I wrote up a demonstration where one link
>> order causes a SIGFPE and another doesn't (and the program is well
>> defined, as far as I can tell).  All TUs are compiled with -O3.  This is also
>> an instance where we don't actually speculate an inline function, but only
>> DSE across it (after deducing readnone).
>> 
>> Here's the link https://github.com/sanjoy/comdat-ipo
> 
> This test case "works" with gcc 5.3.0 too, afaict.
> 
> This is what I used:
> 
> Using built-in specs.
> COLLECT_GCC=/usr/local/Cellar/gcc/5.3.0/bin/x86_64-apple-darwin15.0.0-g++-5
> COLLECT_LTO_WRAPPER=/usr/local/Cellar/gcc/5.3.0/libexec/gcc/x86_64-apple-darwin15.0.0/5.3.0/lto-wrapper
> Target: x86_64-apple-darwin15.0.0
> Configured with: ../configure --build=x86_64-apple-darwin15.0.0
> --prefix=/usr/local/Cellar/gcc/5.3.0
> --libdir=/usr/local/Cellar/gcc/5.3.0/lib/gcc/5
> --enable-languages=c,c++,objc,obj-c++,fortran --program-suffix=-5
> --with-gmp=/usr/local/opt/gmp --with-mpfr=/usr/local/opt/mpfr
> --with-mpc=/usr/local/opt/libmpc --with-isl=/usr/local/opt/isl
> --with-system-zlib --enable-libstdcxx-time=yes
> --enable-stage1-checking --enable-checking=release --enable-lto
> --with-build-config=bootstrap-debug --disable-werror
> --with-pkgversion='Homebrew gcc 5.3.0'
> --with-bugurl=https://github.com/Homebrew/homebrew/issues
> --enable-plugin --disable-nls --enable-multilib
> Thread model: posix
> gcc version 5.3.0 (Homebrew gcc 5.3.0)
> 
> -- Sanjoy
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