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Diffstat (limited to 'BUILDING.md')
| -rw-r--r-- | BUILDING.md | 12 |
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diff --git a/BUILDING.md b/BUILDING.md index 5631ded..522bee1 100644 --- a/BUILDING.md +++ b/BUILDING.md @@ -134,6 +134,18 @@ to enabling the corresponding ARM feature. Note that if a feature is enabled in this way, but not actually supported at run-time, BoringSSL will likely crash. +## Assembling ARMv8 with Clang + +In order to support the ARMv8 crypto instructions, Clang requires that the +architecture be `armv8-a+crypto`. However, setting that as a general build flag +would allow the compiler to assume that crypto instructions are *always* +supported, even without testing for them. + +It's possible to set the architecture in an assembly file using the `.arch` +directive, but only very recent versions of Clang support this. If +`BORINGSSL_CLANG_SUPPORTS_DOT_ARCH` is defined then `.arch` directives will be +used with Clang, otherwise you may need to craft acceptable assembler flags. + # Running tests There are two sets of tests: the C/C++ tests and the blackbox tests. For former |