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[Bug target/36992] Very stange code for _mm_move_epi64
- From: "ubizjak at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 2 Aug 2008 13:08:59 -0000
- Subject: [Bug target/36992] Very stange code for _mm_move_epi64
- References: <bug-36992-682@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #9 from ubizjak at gmail dot com 2008-08-02 13:08 -------
Hm, IA-32 Intel® Architecture Software Developer?s Manual says about movq:
Operation
MOVQ instruction when operating on MMX technology registers and memory
locations:
DEST ← SRC;
MOVQ instruction when source and destination operands are XMM registers:
DEST[63:0] ← SRC[63:0];
MOVQ instruction when source operand is XMM register and destination
operand is memory location:
DEST ← SRC[63:0];
MOVQ instruction when source operand is memory location and destination
operand is XMM register:
DEST[63:0] ← SRC;
DEST[127:64] ← 0000000000000000H;
Please note, that the documentation doesn't say anything about clearing
destination bits [127:64] when both source and destination are in XMM register.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36992