From: Richard Henderson <rth@twiddle.net>
To: Paolo Bonzini <pbonzini@redhat.com>, qemu-devel@nongnu.org
Cc: ehabkost@redhat.com
Subject: Re: [Qemu-devel] [PATCH 05/14] target-i386: Enable control registers for MPX
Date: Wed, 10 Feb 2016 06:08:47 +1100 [thread overview]
Message-ID: <56BA393F.40607@twiddle.net> (raw)
In-Reply-To: <56B9E971.9070509@redhat.com>
On 02/10/2016 12:28 AM, Paolo Bonzini wrote:
> On 09/07/2015 10:17, Richard Henderson wrote:
>> + /* Disallow enabling only half of MPX. */
>> + if ((mask ^ (mask * (XSTATE_BNDCSR / XSTATE_BNDREGS))) & XSTATE_BNDCSR) {
>
> I'm refreshing patches 1-4 to add PKE support, and this caught my eye...
>
> What about just
>
> if (!!(mask & XSTATE_BNDCSR) != !!(mask & XSTATE_BNDREGS))
>
> ?
Hmph. Missed optimization for your version.
It is a bit more readable though, I admit...
r~
void bar();
void foo(unsigned mask)
{
if ((mask ^ (mask * 4)) & 8) {
bar();
}
}
void baz(unsigned mask)
{
if (!!(mask & 8) != !!(mask & 2)) {
bar();
}
}
foo:
leal 0(,%rdi,4), %eax
xorl %eax, %edi
andl $8, %edi
jne .L4
...
baz:
movl %edi, %eax
shrl %edi
shrl $3, %eax
andl $1, %edi
andl $1, %eax
cmpb %dil, %al
je .L5
...
clang_baz:
movl %edi, %eax
shrl $3, %eax
shrl %edi
xorl %eax, %edi
testb $1, %dil
jne .LBB1_2
next prev parent reply other threads:[~2016-02-09 19:09 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-09 8:17 [Qemu-devel] [PATCH 00/14] target-i386: Implement MPX extension Richard Henderson
2015-07-09 8:17 ` [Qemu-devel] [PATCH 01/14] target-i386: Split fxsave/fxrstor implementation Richard Henderson
2015-07-09 8:17 ` [Qemu-devel] [PATCH 02/14] target-i386: Rearrange processing of 0F 01 Richard Henderson
2015-07-09 8:17 ` [Qemu-devel] [PATCH 03/14] target-i386: Add XSAVE extension Richard Henderson
2015-07-09 13:16 ` Paolo Bonzini
2015-07-09 8:17 ` [Qemu-devel] [PATCH 04/14] target-i386: Implement XSAVEOPT Richard Henderson
2015-07-09 13:06 ` Paolo Bonzini
2015-07-10 7:00 ` Richard Henderson
2015-07-09 8:17 ` [Qemu-devel] [PATCH 05/14] target-i386: Enable control registers for MPX Richard Henderson
2015-07-09 13:12 ` Paolo Bonzini
2015-07-09 13:18 ` Paolo Bonzini
2015-07-10 7:44 ` Richard Henderson
2016-02-09 13:28 ` Paolo Bonzini
2016-02-09 15:50 ` Eric Blake
2016-02-09 15:50 ` Paolo Bonzini
2016-02-09 19:08 ` Richard Henderson [this message]
2015-07-09 8:17 ` [Qemu-devel] [PATCH 06/14] target-i386: Perform set/reset_inhibit_irq inline Richard Henderson
2015-07-09 8:17 ` [Qemu-devel] [PATCH 07/14] target-i386: Split up gen_lea_modrm Richard Henderson
2015-07-09 8:17 ` [Qemu-devel] [PATCH 08/14] target-i386: Implement BNDMK Richard Henderson
2015-07-09 8:17 ` [Qemu-devel] [PATCH 09/14] target-i386: Implement BNDMOV Richard Henderson
2015-07-09 8:17 ` [Qemu-devel] [PATCH 10/14] target-i386: Implement BNDCL, BNDCU, BNDCN Richard Henderson
2015-07-09 8:17 ` [Qemu-devel] [PATCH 11/14] target-i386: Update BNDSTATUS for exceptions raised by BOUND Richard Henderson
2015-07-09 8:17 ` [Qemu-devel] [PATCH 12/14] target-i386: Implement BNDLDX, BNDSTX Richard Henderson
2015-07-09 8:17 ` [Qemu-devel] [PATCH 13/14] target-i386: Clear bndregs during legacy near jumps Richard Henderson
2015-07-09 8:17 ` [Qemu-devel] [PATCH 14/14] target-i386: Enable XCR0 features for user-mode Richard Henderson
2015-07-09 13:15 ` Paolo Bonzini
2015-07-10 7:24 ` Richard Henderson
2015-07-10 9:36 ` Paolo Bonzini
2015-11-17 17:43 ` [Qemu-devel] [PATCH 00/14] target-i386: Implement MPX extension Paolo Bonzini
2015-11-18 9:43 ` Richard Henderson
2015-11-18 10:13 ` Paolo Bonzini
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