From: Segher Boessenkool <segher@kernel.crashing.org>
To: "Richard Earnshaw (lists)" <Richard.Earnshaw@arm.com>,
Richard Henderson <richard.henderson@linaro.org>,
gcc-patches@gcc.gnu.org, marcus.shawcroft@arm.com,
Wilco.Dijkstra@arm.com, richard.sandiford@arm.com
Subject: Re: [PATCH v2 00/11] aarch64: Implement TImode comparisons
Date: Tue, 7 Apr 2020 15:27:45 -0500 [thread overview]
Message-ID: <20200407202745.GY26902@gate.crashing.org> (raw)
In-Reply-To: <mptlfn8uai9.fsf@arm.com>
On Mon, Apr 06, 2020 at 12:19:42PM +0100, Richard Sandiford wrote:
> The reason I'm not keen on using special modes for this case is that
> they'd describe one way in which the result can be used rather than
> describing what the instruction actually does. The instruction really
> does set all four flags to useful values. The "problem" is that they're
> not the values associated with a compare between two values, so representing
> them that way will always lose information.
CC modes describe how the flags are set, not how the flags are used.
You cannot easily describe the V bit setting with a compare (it needs
a mode bigger than the register), is that what you mean?
Segher
next prev parent reply other threads:[~2020-04-07 20:27 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-02 18:53 Richard Henderson
2020-04-02 18:53 ` [PATCH v2 01/11] aarch64: Accept 0 as first argument to compares Richard Henderson
2020-04-02 18:53 ` [PATCH v2 02/11] aarch64: Accept zeros in add<GPI>3_carryin Richard Henderson
2020-04-02 18:53 ` [PATCH v2 03/11] aarch64: Provide expander for sub<GPI>3_compare1 Richard Henderson
2020-04-02 18:53 ` [PATCH v2 04/11] aarch64: Introduce aarch64_expand_addsubti Richard Henderson
2020-04-02 18:53 ` [PATCH v2 05/11] aarch64: Use UNSPEC_SBCS for subtract-with-borrow + output flags Richard Henderson
2020-04-09 21:52 ` Segher Boessenkool
2020-04-10 3:50 ` Richard Henderson
2020-04-02 18:53 ` [PATCH v2 06/11] aarch64: Use UNSPEC_ADCS for add-with-carry " Richard Henderson
2020-04-02 18:53 ` [PATCH v2 07/11] aarch64: Remove CC_ADCmode Richard Henderson
2020-04-02 18:53 ` [PATCH v2 08/11] aarch64: Accept -1 as second argument to add<mode>3_carryin Richard Henderson
2020-04-02 18:53 ` [PATCH v2 09/11] aarch64: Adjust result of aarch64_gen_compare_reg Richard Henderson
2020-04-02 18:53 ` [PATCH v2 10/11] aarch64: Implement TImode comparisons Richard Henderson
2020-04-02 18:53 ` [PATCH v2 11/11] aarch64: Implement absti2 Richard Henderson
2020-04-02 18:55 ` [PATCH v2 00/11] aarch64: Implement TImode comparisons Richard Henderson
2020-04-03 11:34 ` Richard Earnshaw (lists)
2020-04-03 12:27 ` Richard Sandiford
2020-04-03 13:17 ` Richard Earnshaw (lists)
2020-04-03 15:03 ` Richard Sandiford
2020-04-06 9:27 ` Richard Earnshaw (lists)
2020-04-06 11:19 ` Richard Sandiford
2020-04-06 12:22 ` Richard Biener
2020-04-08 9:10 ` Richard Sandiford
2020-04-07 9:52 ` Richard Earnshaw (lists)
2020-04-07 16:32 ` Richard Sandiford
2020-04-07 17:05 ` Richard Henderson
2020-04-07 19:43 ` Segher Boessenkool
2020-04-07 20:27 ` Segher Boessenkool [this message]
2020-04-07 21:43 ` Richard Henderson
2020-04-07 23:58 ` Segher Boessenkool
2020-04-08 0:50 ` Richard Henderson
2020-04-08 20:56 ` Segher Boessenkool
2020-04-08 9:06 ` Richard Sandiford
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