RFR: 8295159: DSO created with -ffast-math breaks Java floating-point arithmetic [v8]

[Andrew Haley]

On Wed, 11 Oct 2023 14:03:24 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> Andrew Haley has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 28 commits:
>> 
>>  - Merge branch 'JDK-8295159' of https://github.com/theRealAph/jdk into JDK-8295159
>>  - Fix LLVM
>>  - Give x32 bug its own ID.
>>  - cleanup
>>  - Fix conditional compilation
>>  - Remove x32 handling
>>  - Stash x86-32 changes
>>  - MacOS
>>  - AArch64
>>  - x86-32 changes
>>  - ... and 18 more: https://git.openjdk.org/jdk/compare/cef9fff0...c56adbd9
>
> src/hotspot/os/bsd/os_bsd.cpp line 976:
> 
>> 974: // same architecture as Hotspot is running on
>> 975: 
>> 976: void *os::Bsd::dlopen_helper(const char *filename, int mode) {
> 
> I thought BSD is switching to clang.

What difference does it make if it does?

> src/hotspot/os/bsd/os_bsd.cpp line 1001:
> 
>> 999:     static const volatile double thresh
>> 1000:       = jdouble_cast(0x0000000000000003); // 0x0.0000000000003p-1022;
>> 1001:     if (unity + thresh == unity || -unity - thresh == -unity) {
> 
> Could this expression happen to be precomputed by the compiler at build time? Maybe make the parts volatile?

`thresh` is volatile. What more is needed?

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/10661#discussion_r1355424964
PR Review Comment: https://git.openjdk.org/jdk/pull/10661#discussion_r1355423807