[PATCH] D12052: [X86][SSE] Add _mm_undefined_* intrinsics

Simon Pilgrim via cfe-commits cfe-commits at lists.llvm.org
Sun Aug 16 03:04:55 PDT 2015

RKSimon added a comment.

Yes using that uninitialized value has worried me as well. I originally set it to zero (and considered using __ LINE __ or __ COUNTER __) but both introduce defined behaviour that I could see causing all sorts of problems further down the line in debug vs release builds. How undefined do we want our undefined to be? ;-)

I can create __builtin_ia32_undef64mmx / __builtin_ia32_undef128 / __builtin_ia32_undef256 / __builtin_ia32_undef512 if nobody can think of a better alternative?



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