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From: "foom at fuhm dot net" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug target/98495] New: X86 _mm_extract_pi16 incorrectly sign extends result Date: Fri, 01 Jan 2021 04:14:42 +0000 [thread overview] Message-ID: <bug-98495-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98495 Bug ID: 98495 Summary: X86 _mm_extract_pi16 incorrectly sign extends result Product: gcc Version: 11.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: target Assignee: unassigned at gcc dot gnu.org Reporter: foom at fuhm dot net Target Milestone: --- #include <xmmintrin.h> int test(__m64 a) { return _mm_extract_pi16 (a, 0); } Compiles to (x86_64 gcc, -O2): pextrw $0, %xmm0, %eax cwtl ret Which results in the value being sign-extended from 16-bits to 32-bits. The intel docs for PEXTRW state that the upper bits are zeroed, and state that _mm_extract_pi16 is supposed to implement PEXTRW. So, the expected result is no sign extension: pextrw $0, %xmm0, %eax ret I'd note that this is not a regression due to the new MMX with SSE2 changes -- GCC has had this bug as far back as I can see. It is currently present on trunk both for the MMX and SSE2 implementations. Both clang and MSVC zero-extend rather than sign-extend. And, for that matter, GCC's _mm_extract_epi16 function _also_ zero-extends -- it was fixed in PR45336 for GCC 4.6.
next reply other threads:[~2021-01-01 4:14 UTC|newest] Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-01-01 4:14 foom at fuhm dot net [this message] 2021-01-01 13:06 ` [Bug target/98495] " hjl.tools at gmail dot com 2021-01-01 13:35 ` hjl.tools at gmail dot com 2021-01-05 13:08 ` cvs-commit at gcc dot gnu.org 2021-01-05 19:23 ` cvs-commit at gcc dot gnu.org 2021-04-27 11:39 ` jakub at gcc dot gnu.org 2021-07-28 7:05 ` rguenth at gcc dot gnu.org 2022-04-21 7:48 ` rguenth at gcc dot gnu.org 2023-05-29 10:03 ` jakub at gcc dot gnu.org
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