Date: Fri, 1 Nov 2013 22:43:20 +0700 From: Alexey Dokuchaev <danfe@nsu.ru> To: hackers@freebsd.org Subject: Re: SSE2 intrinsics: gcc46 vs. clang contradiction Message-ID: <20131101154320.GA11359@regency.nsu.ru> In-Reply-To: <20131101124645.GA73456@regency.nsu.ru> References: <20131101124645.GA73456@regency.nsu.ru>
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On Fri, Nov 01, 2013 at 07:46:45PM +0700, Alexey Dokuchaev wrote: > What adds to confusion, in their manual [1] Intel spells them differently > themselves: first, in the table, it says: > > _mm_movpi64_epi64 Move MOVDQ2Q > ^^^^^ > > Then later, when they describe what it does, it says: > > __m128i _mm_movpi64_pi64(__m64 a) > ^^^^ > Moves the 64 bits of a to the lower 64 bits of the result, zeroing the > upper bits. Microsoft (http://msdn.microsoft.com/en-us/library/has3d153(v=vs.90).aspx) defines these two: _mm_movepi64_pi64 MOVDQ2Q Move _mm_movpi64_epi64 MOVQ2DQ Move That is: __m64 _mm_movepi64_pi64 (__m128i a); MOVDQ2Q r0 := a0 ; __m128i _mm_movpi64_epi64 (__m64 a); MOVDQ2Q r0 := a0 ; r1 := 0X0 ; Cf. Intel's: _mm_movepi64_pi64 Move MOVDQ2Q _mm_movpi64_epi64 Move MOVDQ2Q __m64 _mm_movepi64_pi64(__m128i a) Returns the lower 64 bits of a as an __m64 type: R0 := a0 __m128i _mm_movpi64_pi64(__m64 a) Moves the 64 bits of a to the lower 64 bits of the result, zeroing the upper bits: R0 := a0, R1 = 0X0 Assuming that both documents correctly assign instructions to function names (bonus clue: it also makes them symmetrical), then _mm_movpi64_pi64 is indeed a typo and Clang's header is wrong, while GCC's is correct: it should read _mm_movpi64_epi64(), not _mm_movpi64_pi64(). ./danfe
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