From: Segher Boessenkool <segher@kernel.crashing.org>
To: Richard Henderson <richard.henderson@linaro.org>
Cc: gcc-patches@gcc.gnu.org, richard.earnshaw@arm.com,
marcus.shawcroft@arm.com, kyrylo.tkachov@arm.com,
Wilco.Dijkstra@arm.com, richard.sandiford@arm.com
Subject: Re: [PATCH v2 3/9] aarch64: Add <su>cmp_*_carryinC patterns
Date: Wed, 1 Apr 2020 07:37:35 -0500 [thread overview]
Message-ID: <20200401123735.GX22482@gate.crashing.org> (raw)
In-Reply-To: <e87f5d57-a574-387f-5a84-5bbc0b0ccdb7@linaro.org>
On Tue, Mar 31, 2020 at 03:44:51PM -0700, Richard Henderson wrote:
> If we add more CC modes, does that mean that we have to improve SELECT_CC_MODE
> to match those patterns? Or do we add new CC modes just so that combine's use
> of SELECT_CC_MODE *cannot* match them?
Adding new CC modes isn't helpful if nothing ever generates them. To
have combine decide to use a different CC mode for a combined insn, you
need SELECT_CC_MODE.
The result of a combination is always valid (as RTL) with the original
CC mode, but such an insn might not exist, and perhaps it does exist
with some weaker CC mode (or more general CC mode, in some cases).
Segher
next prev parent reply other threads:[~2020-04-01 12:37 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-21 2:42 [PATCH v2 0/9] aarch64: Implement TImode comparisons Richard Henderson
2020-03-21 2:42 ` [PATCH v2 1/9] aarch64: Accept 0 as first argument to compares Richard Henderson
2020-03-31 16:55 ` Richard Sandiford
2020-03-31 17:15 ` Richard Henderson
2020-03-21 2:42 ` [PATCH v2 2/9] aarch64: Accept zeros in add<GPI>3_carryin Richard Henderson
2020-03-21 2:42 ` [PATCH v2 3/9] aarch64: Add <su>cmp_*_carryinC patterns Richard Henderson
2020-03-22 19:30 ` Segher Boessenkool
2020-03-22 20:40 ` Richard Henderson
2020-03-31 18:34 ` Richard Sandiford
2020-03-31 22:44 ` Richard Henderson
2020-04-01 12:37 ` Segher Boessenkool [this message]
2020-04-01 16:28 ` Richard Sandiford
2020-04-01 17:14 ` Richard Henderson
2020-03-21 2:42 ` [PATCH v2 4/9] aarch64: Add <su>cmp<GPI>_carryinC_m2 Richard Henderson
2020-03-21 2:42 ` [PATCH v2 5/9] aarch64: Provide expander for sub<GPI>3_compare1 Richard Henderson
2020-03-21 2:42 ` [PATCH v2 6/9] aarch64: Introduce aarch64_expand_addsubti Richard Henderson
2020-03-21 2:42 ` [PATCH v2 7/9] aarch64: Adjust result of aarch64_gen_compare_reg Richard Henderson
2020-03-22 21:55 ` Segher Boessenkool
2020-03-22 22:21 ` Richard Henderson
2020-03-21 2:42 ` [PATCH v2 8/9] aarch64: Implement TImode comparisons Richard Henderson
2020-03-21 2:42 ` [PATCH v2 9/9] aarch64: Implement absti2 Richard Henderson
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