- [Notes on multi-threading](#notes-on-multi-threading)
- [Notes on shared libraries](#notes-on-shared-libraries)
- [Notes on random number generation](#notes-on-random-number-generation)
+ - [Notes on assembler modules compilation](#notes-on-assembler-modules-compilation)
Prerequisites
=============
$ mms clean ! (or mmk) OpenVMS
$ nmake clean # Windows
-Assembler error messages can sometimes be sidestepped by using the
-`no-asm` configuration option.
+Assembler error messages can sometimes be sidestepped by using the `no-asm`
+configuration option. See also [notes](#notes-on-assembler-modules-compilation).
Compiling parts of OpenSSL with gcc and others with the system compiler will
result in unresolved symbols on some systems.
the CSPRNG manually. Please check out the manual pages for `RAND_add()`,
`RAND_bytes()`, `RAND_egd()`, and the FAQ for more information.
+Notes on assembler modules compilation
+--------------------------------------
+
+Compilation of some code paths in assembler modules might depend on whether the
+current assembler version supports certain ISA extensions or not. Code paths
+that use the AES-NI, PCLMULQDQ, SSSE3, and SHA extensions are always assembled.
+Apart from that, the minimum requirements for the assembler versions are shown
+in the table below:
+
+| ISA extension | GNU as | nasm | llvm |
+|---------------|--------|--------|---------|
+| AVX | 2.19 | 2.09 | 3.0 |
+| AVX2 | 2.22 | 2.10 | 3.1 |
+| ADCX/ADOX | 2.23 | 2.10 | 3.3 |
+| AVX512 | 2.25 | 2.11.8 | 3.6 (*) |
+| AVX512IFMA | 2.26 | 2.11.8 | 6.0 (*) |
+| VAES | 2.30 | 2.13.3 | 6.0 (*) |
+
+---
+
+(*) Even though AVX512 support was implemented in llvm 3.6, prior to version 7.0
+an explicit -march flag was apparently required to compile assembly modules. But
+then the compiler generates processor-specific code, which in turn contradicts
+the idea of performing dispatch at run-time, which is facilitated by the special
+variable `OPENSSL_ia32cap`. For versions older than 7.0, it is possible to work
+around the problem by forcing the build procedure to use the following script:
+
+ #!/bin/sh
+ exec clang -no-integrated-as "$@"
+
+instead of the real clang. In which case it doesn't matter what clang version
+is used, as it is the version of the GNU assembler that will be checked.
+
+---
+
<!-- Links -->
[openssl-users]:
C<:~0x20> would disable AVX2 code paths, and C<:0> - all post-AVX
extensions.
-It should be noted that whether or not some of the most "fancy"
-extension code paths are actually assembled depends on current assembler
-version. Base minimum of AES-NI/PCLMULQDQ, SSSE3 and SHA extension code
-paths are always assembled. Apart from that, minimum assembler version
-requirements are summarized in below table:
-
- Extension | GNU as | nasm | llvm
- ------------+--------+--------+--------
- AVX | 2.19 | 2.09 | 3.0
- AVX2 | 2.22 | 2.10 | 3.1
- ADCX/ADOX | 2.23 | 2.10 | 3.3
- AVX512 | 2.25 | 2.11.8 | see NOTES
- AVX512IFMA | 2.26 | 2.11.8 | see NOTES
- VAES | 2.30 | 2.13.3 |
-
-=head1 NOTES
-
-Even though AVX512 support was implemented in llvm 3.6, compilation of
-assembly modules apparently requires explicit -march flag. But then
-compiler generates processor-specific code, which in turn contradicts
-the mere idea of run-time switch execution facilitated by the variable
-in question. Till the limitation is lifted, it's possible to work around
-the problem by making build procedure use following script:
-
- #!/bin/sh
- exec clang -no-integrated-as "$@"
-
-instead of real clang. In which case it doesn't matter which clang
-version is used, as it is GNU assembler version that will be checked.
-
=head1 RETURN VALUES
Not available.