Add additional comments

1 files changed, 7 insertions, 5 deletions

diff --git a/config.h b/config.h
index 08f9f02d..6c3c8c3b 100644
--- a/config.h
+++ b/config.h
@@ -297,11 +297,13 @@ const lword LWORD_MAX = W64LIT(0xffffffffffffffff);
 // Also see https://bugs.llvm.org/show_bug.cgi?id=39895 .

 // #define CRYPTOPP_DISABLE_MIXED_ASM 1

 

-// Several compilers discard SIMD code that loads unaligned data. For example,

-// Power7 can load unaligned data using vec_vsx_ld but GCC and Clang require

-// 16-byte aligned arrays when using builtin function. Define this to disable

-// Crypto++ code that uses problematic builtins or intrinsics.

-// #define CRYPTOPP_BUGGY_SIMD_LOAD_AND_STORE 1

+// Several compilers discard SIMD code that loads unaligned data. The symptom

+// is often self test failures and UBsan findings of unaligned loads. For

+// example, Power7 can load unaligned data using vec_vsx_ld but some versions

+// of GCC and Clang require 16-byte aligned arrays when using the builtin

+// function. It is not limited to SSE and PowerPC code. Define this to disable

+// Crypto++ code that uses potentially problematic builtins or intrinsics.

+#define CRYPTOPP_BUGGY_SIMD_LOAD_AND_STORE 1

 

 // This list will probably grow over time as more compilers are identified.

 #if defined(CRYPTOPP_BUGGY_SIMD_LOAD_AND_STORE)