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From: "Maciej W. Rozycki" <macro@imgtec.com>
To: Richard Henderson <rth@twiddle.net>
Cc: James Hogan <james.hogan@imgtec.com>,
	Leon Alrae <Leon.Alrae@imgtec.com>,
	qemu-devel@nongnu.org, Aurelien Jarno <aurelien@aurel32.net>
Subject: Re: [Qemu-devel] [PATCH 14/15] tcg-mips: Use mipsr6 instructions in branches
Date: Tue, 9 Feb 2016 18:46:03 +0000	[thread overview]
Message-ID: <alpine.DEB.2.00.1602091731220.15885@tp.orcam.me.uk> (raw)
In-Reply-To: <56BA1E22.5010708@twiddle.net>

On Tue, 9 Feb 2016, Richard Henderson wrote:

> > So to be correct + efficient, it should only put the nop in if the next
> > generated instruction is a CTI. I imagine that would be a bit messy /
> > fragile, but maybe doable? I haven't looked too deeply.
> 
> Ouch, I didn't notice this about these insns.
> 
> I suppose this might be rare enough that it's still worth thinking about.  Off
> the top of my head I can't think of any way to save extra state, but perhaps
> just looking back at the previous insn's major opcode is enough when emitting
> any forbidden insn.

 FWIW I think this is a reasonable approach, applying to the regular MIPS 
ISA where the size of the instruction word is fixed so you can look at the 
preceding instruction in a reproducible manner.  And in the microMIPSr6 
ISA there are no forbidden slots, so no issue there in the first place.

  Maciej

  reply	other threads:[~2016-02-09 18:46 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-02-09 10:39 [Qemu-devel] [PATCH 00/15] tcg mips64 and mipsr6 improvements Richard Henderson
2016-02-09 10:39 ` [Qemu-devel] [PATCH 01/15] tcg-mips: Add mips64 opcodes Richard Henderson
2016-02-09 10:39 ` [Qemu-devel] [PATCH 02/15] tcg-mips: Support 64-bit opcodes Richard Henderson
2016-02-09 15:24   ` James Hogan
2016-02-09 17:16     ` Richard Henderson
2016-02-09 10:39 ` [Qemu-devel] [PATCH 03/15] tcg-mips: Adjust move functions for mips64 Richard Henderson
2016-02-09 10:39 ` [Qemu-devel] [PATCH 04/15] tcg-mips: Adjust load/store " Richard Henderson
2016-02-09 10:39 ` [Qemu-devel] [PATCH 05/15] tcg-mips: Adjust prologue " Richard Henderson
2016-02-09 10:39 ` [Qemu-devel] [PATCH 06/15] tcg-mips: Add tcg unwind info Richard Henderson
2016-02-09 10:39 ` [Qemu-devel] [PATCH 07/15] tcg-mips: Adjust qemu_ld/st for mips64 Richard Henderson
2016-02-10 16:34   ` James Hogan
2016-02-10 17:35     ` Richard Henderson
2016-02-09 10:39 ` [Qemu-devel] [PATCH 08/15] tcg-mips: Adjust calling conventions " Richard Henderson
2016-02-09 10:39 ` [Qemu-devel] [PATCH 09/15] tcg-mips: Fix exit_tb " Richard Henderson
2016-02-09 10:39 ` [Qemu-devel] [PATCH 10/15] tcg-mips: Move bswap code to subroutines Richard Henderson
2016-02-09 10:39 ` [Qemu-devel] [PATCH 11/15] tcg-mips: Use mips64r6 instructions in tcg_out_movi Richard Henderson
2016-02-09 16:50   ` James Hogan
2016-02-09 17:20     ` Richard Henderson
2016-02-09 17:25     ` Richard Henderson
2016-02-10  0:32     ` James Hogan
2016-02-09 10:40 ` [Qemu-devel] [PATCH 12/15] tcg-mips: Use mips64r6 instructions in tcg_out_ldst Richard Henderson
2016-02-09 10:40 ` [Qemu-devel] [PATCH 13/15] tcg-mips: Use mips64r6 instructions in constant addition Richard Henderson
2016-02-09 10:40 ` [Qemu-devel] [PATCH 14/15] tcg-mips: Use mipsr6 instructions in branches Richard Henderson
2016-02-09 16:22   ` James Hogan
2016-02-09 17:13     ` Richard Henderson
2016-02-09 18:46       ` Maciej W. Rozycki [this message]
2016-02-10  0:20     ` James Hogan
2016-02-09 10:40 ` [Qemu-devel] [PATCH 15/15] tcg-mips: Use mipsr6 instructions in calls Richard Henderson
2016-02-10 12:49   ` James Hogan

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