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[Bug target/80820] _mm_set_epi64x shouldn't store/reload for -mtune=haswell, Zen should avoid store/reload, and generic should think about it.
- From: "peter at cordes dot ca" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Fri, 19 May 2017 21:47:42 +0000
- Subject: [Bug target/80820] _mm_set_epi64x shouldn't store/reload for -mtune=haswell, Zen should avoid store/reload, and generic should think about it.
- Auto-submitted: auto-generated
- References: <bug-80820-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80820
--- Comment #2 from Peter Cordes <peter at cordes dot ca> ---
See also https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80833.
gcc -m32 does an even worse job of getting int64_t into an xmm reg, e.g. as
part of a 64-bit atomic store.
We get a store-forwarding failure from code like this, even with -march=haswell
movl %eax, (%esp)
movl %edx, 4(%esp)
movq (%esp), %xmm0