From: Jeff Law <law@redhat.com>
To: gcc-patches@gcc.gnu.org, richard.sandiford@arm.com
Subject: Re: [14/23] simplify-rtx: Put simplify routines into a class
Date: Mon, 30 Nov 2020 12:54:15 -0700 [thread overview]
Message-ID: <f2162d6a-4433-8fa3-396a-7c7ad5857158@redhat.com> (raw)
In-Reply-To: <mptmtzl7jpu.fsf@arm.com>
On 11/13/20 1:18 AM, Richard Sandiford via Gcc-patches wrote:
> One of the recurring warts of RTL is that multiplication by a power
> of 2 is represented as a MULT inside a MEM but as an ASHIFT outside
> a MEM. It would obviously be better if we didn't have this kind of
> context sensitivity, but it would be difficult to remove.
>
> Currently the simplify-rtx.c routines are hard-coded for the
> ASHIFT form. This means that some callers have to convert the
> ASHIFTs “back” into MULTs after calling the simplify-rtx.c
> routines; see fwprop.c:canonicalize_address for an example.
>
> I think we can relieve some of the pain by wrapping the simplify-rtx.c
> routines in a simple class that tracks whether the expression occurs
> in a MEM or not, so that no post-processing is needed.
>
> An obvious concern is whether passing the “this” pointer around
> will slow things down or bloat the code. I can't measure any
> increase in compile time after applying the patch. Sizewise,
> simplify-rtx.o text increases by 2.3% in default-checking builds
> and 4.1% in release-checking builds.
>
> I realise the MULT/ASHIFT thing isn't the most palatable
> reason for doing this, but I think it might be useful for
> other things in future, such as using local nonzero_bits
> hooks/virtual functions instead of the global hooks.
>
> The obvious alternative would be to add a static variable
> and hope that it is always updated correctly.
I think a static would be step in the wrong direction and I'm generally
in favor using classes, particularly when there's contextual information
we want to query. Shoving things into a class allows us to reason about
when/how that contextual information is used.
>
> Later patches make use of this.
>
> gcc/
> * rtl.h (simplify_context): New class.
> (simplify_unary_operation, simplify_binary_operation): Use it.
> (simplify_ternary_operation, simplify_relational_operation): Likewise.
> (simplify_subreg, simplify_gen_unary, simplify_gen_binary): Likewise.
> (simplify_gen_ternary, simplify_gen_relational): Likewise.
> (simplify_gen_subreg, lowpart_subreg): Likewise.
> * simplify-rtx.c (simplify_gen_binary): Turn into a member function
> of simplify_context.
> (simplify_gen_unary, simplify_gen_ternary, simplify_gen_relational)
> (simplify_truncation, simplify_unary_operation): Likewise.
> (simplify_unary_operation_1, simplify_byte_swapping_operation)
> (simplify_associative_operation, simplify_logical_relational_operation)
> (simplify_binary_operation, simplify_binary_operation_series)
> (simplify_distributive_operation, simplify_plus_minus): Likewise.
> (simplify_relational_operation, simplify_relational_operation_1)
> (simplify_cond_clz_ctz, simplify_merge_mask): Likewise.
> (simplify_ternary_operation, simplify_subreg, simplify_gen_subreg)
> (lowpart_subreg): Likewise.
> (simplify_binary_operation_1): Likewise. Test mem_depth when
> deciding whether the ASHIFT or MULT form is canonical.
> (simplify_merge_mask): Use simplify_context.
I like it. OK for the trunk.
jeff
next prev parent reply other threads:[~2020-11-30 19:54 UTC|newest]
Thread overview: 88+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-13 8:10 [00/23] Make fwprop use an on-the-side RTL SSA representation Richard Sandiford
2020-11-13 8:11 ` [01/23] vec: Silence clang warning Richard Sandiford
2020-11-25 19:58 ` Jeff Law
2020-11-13 8:12 ` [02/23] rtlanal: Remove noop_move_p REG_EQUAL condition Richard Sandiford
2020-11-25 20:00 ` Jeff Law
2020-11-13 8:12 ` [03/23] reginfo: Add a global_reg_set Richard Sandiford
2020-11-25 20:01 ` Jeff Law
2020-11-13 8:13 ` [04/23] Move iterator_range to a new iterator-utils.h file Richard Sandiford
2020-11-25 20:02 ` Jeff Law
2020-11-13 8:13 ` [05/23] Add more iterator utilities Richard Sandiford
2020-11-25 20:12 ` Jeff Law
2020-11-13 8:14 ` [06/23] Add an RAII class for managing obstacks Richard Sandiford
2020-11-25 20:15 ` Jeff Law
2020-11-13 8:14 ` [07/23] Add a class that multiplexes two pointer types Richard Sandiford
2020-11-25 20:23 ` Jeff Law
2020-11-26 16:15 ` Richard Sandiford
2020-11-30 1:28 ` Jeff Law
2020-11-25 23:33 ` Martin Sebor
2020-11-26 17:06 ` Richard Sandiford
2020-11-27 18:12 ` Richard Sandiford
2020-11-28 0:17 ` Martin Sebor
2020-12-17 0:17 ` Richard Sandiford
2020-12-17 14:21 ` Tom Tromey
2020-12-17 15:38 ` Richard Sandiford
2020-12-17 15:44 ` Nathan Sidwell
2021-01-04 15:32 ` Jeff Law
2020-11-13 8:15 ` [08/23] Add an alternative splay tree implementation Richard Sandiford
2020-12-02 20:36 ` Jeff Law
2020-12-17 0:29 ` Richard Sandiford
2021-01-04 15:27 ` Jeff Law
2021-01-01 8:25 ` Andreas Schwab
2021-01-04 14:53 ` Richard Sandiford
2021-01-04 15:02 ` Andreas Schwab
2021-01-04 15:42 ` Richard Sandiford
2021-01-05 12:13 ` Richard Biener
2020-11-13 8:15 ` [09/23] Add a cut-down version of std::span (array_slice) Richard Sandiford
2020-11-30 19:56 ` Jeff Law
2022-08-03 15:13 ` Martin Jambor
2022-08-03 15:31 ` Richard Sandiford
2022-08-10 16:03 ` Martin Jambor
2022-08-11 6:58 ` Richard Biener
2022-08-16 7:59 ` Richard Sandiford
2020-11-13 8:16 ` [10/23] Tweak the way that is_a is implemented Richard Sandiford
2020-12-02 5:15 ` Jeff Law
2020-11-13 8:16 ` [11/23] Split update_cfg_for_uncondjump out of combine Richard Sandiford
2020-11-30 6:14 ` Jeff Law
2020-11-13 8:17 ` [12/23] Export print-rtl.c:print_insn_with_notes Richard Sandiford
2020-11-25 20:24 ` Jeff Law
2020-11-13 8:18 ` [13/23] recog: Split out a register_asm_p function Richard Sandiford
2020-11-25 20:24 ` Jeff Law
2020-11-13 8:18 ` [14/23] simplify-rtx: Put simplify routines into a class Richard Sandiford
2020-11-30 19:54 ` Jeff Law [this message]
2020-11-13 8:19 ` [15/23] recog: Add a validate_change_xveclen function Richard Sandiford
2020-11-30 20:03 ` Jeff Law
2020-11-13 8:19 ` [16/23] recog: Add a way of temporarily undoing changes Richard Sandiford
2020-11-25 20:27 ` Jeff Law
2020-12-17 0:22 ` Richard Sandiford
2020-11-13 8:20 ` [17/23] recog: Add a class for propagating into insns Richard Sandiford
2020-12-03 22:32 ` Jeff Law
2020-11-13 8:20 ` [18/23] recog: Add an RAII class for undoing insn changes Richard Sandiford
2020-11-25 20:27 ` Jeff Law
2020-11-13 8:20 ` [19/23] rtlanal: Add some new helper classes Richard Sandiford
2020-12-13 17:30 ` Jeff Law
2020-12-14 16:37 ` Richard Sandiford
2020-12-14 20:02 ` Jeff Law
2020-11-13 8:21 ` [20/23] rtlanal: Add simple_regno_set Richard Sandiford
2020-11-25 20:31 ` Jeff Law
2020-12-17 0:47 ` Richard Sandiford
2021-01-04 15:28 ` Jeff Law
2020-11-13 8:22 ` [21/23] doc: Add documentation for rtl-ssa Richard Sandiford
2020-11-30 6:26 ` Jeff Law
2020-11-13 8:23 ` [PATCH 22/23] Add rtl-ssa Richard Sandiford
2020-12-16 3:31 ` Jeff Law
2020-12-17 0:33 ` Richard Sandiford
2020-12-19 20:01 ` Jeff Law
2020-11-13 8:24 ` [PATCH 23/23] fwprop: Rewrite to use RTL SSA Richard Sandiford
2020-12-16 3:52 ` Jeff Law
2020-12-17 0:34 ` Richard Sandiford
2020-11-25 19:58 ` [00/23] Make fwprop use an on-the-side RTL SSA representation Jeff Law
2020-11-26 16:03 ` Richard Sandiford
2020-11-27 15:56 ` Michael Matz
2020-11-27 16:31 ` Richard Sandiford
2020-11-30 21:13 ` Jeff Law
2020-12-01 0:03 ` Michael Matz
2020-12-01 10:15 ` Richard Sandiford
2020-12-02 0:25 ` Jeff Law
2020-11-30 6:45 ` Jeff Law
2020-11-30 14:12 ` Richard Sandiford
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