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received-spf: None (protection.outlook.com: arm.com does not designate permitted sender hosts) spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-originalarrivaltime: 08 Aug 2017 20:18:28.0944 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-Transport-CrossTenantHeadersStamped: HE1PR0802MB2377 X-SW-Source: 2017-08/txt/msg00624.txt.bz2 Correct. It is truncated for integer shift, but not simd shift instructions= . We generate a pattern in the split that only generates the integer shift = instructions. -----Original Message----- From: Richard Kenner [mailto:kenner@vlsi1.ultra.nyu.edu]=20 Sent: Tuesday, August 8, 2017 1:04 PM To: Michael Collison Cc: gcc-patches@gcc.gnu.org; nd ; pinskia@gmail.com Subject: RE: [PATCH] [Aarch64] Optimize subtract in shift counts > Because for integer shift instructions the shift count is truncated.=20 > We ensure that we only use integer shift instructions by emitting a=20 > shift with a mask. This only matches integer shift instructions in the=20 > md file. That's why I asked about SHIFT_COUNT_TRUNCATED. So it's truncated for some= shifts, but not all?