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Re: [PATCH] X86-64: Add -mskip-rax-setup
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: Mike Stump <mikestump at comcast dot net>
- Cc: Uros Bizjak <ubizjak at gmail dot com>, "H. Peter Anvin" <hpa at zytor dot com>, "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>, Rasmus Villemoes <linux at rasmusvillemoes dot dk>, "x86 at kernel dot org" <x86 at kernel dot org>, Andi Kleen <andi at firstfloor dot org>, Ingo Molnar <mingo at redhat dot com>, Thomas Gleixner <tglx at linutronix dot de>
- Date: Thu, 18 Dec 2014 11:35:54 -0800
- Subject: Re: [PATCH] X86-64: Add -mskip-rax-setup
- Authentication-results: sourceware.org; auth=none
- References: <20141218131150 dot GA32638 at intel dot com> <CAFULd4ZaY5USX+CKdzoq1zWL8kZ3VqVx7KGxwb_tQEzbX03u-A at mail dot gmail dot com> <CAFULd4avYqhgA-D7+_w3b0Uk9jaso7JpXQXL2zU56Avs23i1og at mail dot gmail dot com> <CAFULd4asXmUnG+eYW9jyW7EQDLydTUnKUinW7yhRUo+cGauEVA at mail dot gmail dot com> <CAMe9rOq5FVz5D0ug12bzjBMG=VnwgN5H+t734FLPJ4ANXqrMVQ at mail dot gmail dot com> <CAFULd4ZzhaMu_JSXjPaKbaYSLbAa1P3pGcu_UkqEW05Ub4vksw at mail dot gmail dot com> <54930A0A dot 40207 at zytor dot com> <CAFULd4Y+XR-Op9FwAoPbN0y-BHiDOqdnEuxd1hUPKC8yKy-G5g at mail dot gmail dot com> <CAMe9rOpuXiUXTU30pyr+v9Z0dVCzh=_gdCCTataziSuJ_JMwVw at mail dot gmail dot com> <D9D50F9B-8E80-49DF-A34B-E71D48DF3BB0 at comcast dot net>
On Thu, Dec 18, 2014 at 11:22 AM, Mike Stump <mikestump@comcast.net> wrote:
> On Dec 18, 2014, at 9:43 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> + arguments passed in vector registers. This can be used to
>> + optimize Linux kernel.</li>
>
> English, to optimize _the_ Linux kernel?
Updated.
--
H.J.
---
Index: gcc-5/changes.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-5/changes.html,v
retrieving revision 1.52
diff -u -p -r1.52 changes.html
--- gcc-5/changes.html 15 Dec 2014 19:55:08 -0000 1.52
+++ gcc-5/changes.html 18 Dec 2014 19:35:28 -0000
@@ -444,6 +444,10 @@ void operator delete[] (void *, std::siz
place of the __fentry__ or mcount call, so that a call per function
can be later patched in. This can be used for low overhead tracing or
hot code patching.</li>
+ <li>The new <code>-mskip-rax-setup</code> option to skip setting
+ up RAX register when SSE is disabled and there are no variable
+ arguments passed in vector registers. This can be used to
+ optimize the Linux kernel.</li>
</ul>
<h3 id="sh">SH</h3>