Hello Alex:
On 14/05/24 11:53 pm, Alex Coplan wrote:
> Hi Ajit,
>
> Please can you pay careful attention to the review comments?
>
> In particular, you have ignored my comment about changing the access of
> member functions in ldp_bb_info several times now (on at least three
> patch reviews).
>
> Likewise on multiple occasions you've only partially implemented a piece
> of review feedback (e.g. applying the "override" keyword to virtual
> overrides).
>
> That all makes it rather tiresome to review your patches.
>
> Also, I realise I should have mentioned this on a previous revision of
> this patch, but I thought we previously agreed (with Richard S) to split
> out the renaming in existing code (e.g. ldp/stp -> "paired access" and
> so on) to a separate patch? That would make this eaiser to review.
>
Sorry for the inconvenience caused. Hopefully I have incorporated
all the comments in v6 version of the patch.
> On 14/05/2024 15:08, Ajit Agarwal wrote:
>> Hello Alex/Richard:
>>
>> All comments are addressed.
>>
>> Common infrastructure of load store pair fusion is divided into target
>> independent and target dependent changed code.
>>
>> Target independent code is the Generic code with pure virtual function
>> to interface betwwen target independent and dependent code.
>>
>> Target dependent code is the implementation of pure virtual function for
>> aarch64 target and the call to target independent code.
>>
>> Bootstrapped on aarch64-linux-gnu.
>>
>> Thanks & Regards
>> Ajit
>>
>>
>>
>> arch64: Preparatory patch to place target independent and
>> dependent changed code in one file
>>
>> Common infrastructure of load store pair fusion is divided into target
>> independent and target dependent changed code.
>>
>> Target independent code is the Generic code with pure virtual function
>> to interface betwwen target independent and dependent code.
>>
>> Target dependent code is the implementation of pure virtual function for
>> aarch64 target and the call to target independent code.
>>
>> 2024-05-14 Ajit Kumar Agarwal <aagar...@linux.ibm.com>
>>
>> gcc/ChangeLog:
>>
>> * config/aarch64/aarch64-ldp-fusion.cc: Place target
>> independent and dependent changed code.
>> ---
>> gcc/config/aarch64/aarch64-ldp-fusion.cc | 526 +++++++++++++++--------
>> 1 file changed, 345 insertions(+), 181 deletions(-)
>>
>> diff --git a/gcc/config/aarch64/aarch64-ldp-fusion.cc
>> b/gcc/config/aarch64/aarch64-ldp-fusion.cc
>> index 1d9caeab05d..e6af4b0570a 100644
>> --- a/gcc/config/aarch64/aarch64-ldp-fusion.cc
>> +++ b/gcc/config/aarch64/aarch64-ldp-fusion.cc
>> @@ -138,6 +138,210 @@ struct alt_base
>> poly_int64 offset;
>> };
>>
>> +// Virtual base class for load/store walkers used in alias analysis.
>> +struct alias_walker
>> +{
>> + virtual bool conflict_p (int &budget) const = 0;
>> + virtual insn_info *insn () const = 0;
>> + virtual bool valid () const = 0;
>> + virtual void advance () = 0;
>> +};
>> +
>> +// This is used in handle_writeback_opportunities describing
>> +// ALL if aarch64_ldp_writeback > 1 otherwise check
>> +// EXISTING if aarch64_ldp_writeback.
>
> Since this enum belongs to the generic interface, it's best if it is
> described in general terms, i.e. the comment shouldn't refer to the
> aarch64 param.
>
> How about:
>
> // When querying handle_writeback_opportunities, this enum is used to
> // qualify which opportunities we are asking about.
>
> then above the EXISTING enumerator, you could say:
>
> // Only those writeback opportunities that arise from existing
> // auto-increment accesses.
>
> and for ALL, you could say:
>
> // All writeback opportunities including those that involve folding
> // base register updates into a non-writeback pair.
>
Addressed in v6 of the patch.
>> +enum class writeback {
>> + ALL,
>> + EXISTING
>> +};
>
> Also, sorry for the very minor nit, but I think it is more logical if we
> flip the order of the enumerators here, i.e. EXISTING should come first.
>
>> +
>> +struct pair_fusion {
>> + pair_fusion ()
>> + {
>> + calculate_dominance_info (CDI_DOMINATORS);
>> + df_analyze ();
>> + crtl->ssa = new rtl_ssa::function_info (cfun);
>> + };
>> +
>> + // Given:
>> + // - an rtx REG_OP, the non-memory operand in a load/store insn,
>> + // - a machine_mode MEM_MODE, the mode of the MEM in that insn, and
>> + // - a boolean LOAD_P (true iff the insn is a load), then:
>> + // return true if the access should be considered an FP/SIMD access.
>> + // Such accesses are segregated from GPR accesses, since we only want
>> + // to form pairs for accesses that use the same register file.
>> + virtual bool fpsimd_op_p (rtx, machine_mode, bool)
>> + {
>> + return false;
>> + }
>> +
>> + // Return true if we should consider forming ldp/stp insns from memory
>
> Replace "ldp/stp insns" with "pairs" here, since this is the generic
> interface.
>
Addressed in v6 of the patch.
>> + // accesses with operand mode MODE at this stage in compilation.
>> + virtual bool pair_operand_mode_ok_p (machine_mode mode) = 0;
>> +
>> + // Return true iff REG_OP is a suitable register operand for a paired
>> + // memory access, where LOAD_P is true if we're asking about loads and
>> + // false for stores. MODE gives the mode of the operand.
>> + virtual bool pair_reg_operand_ok_p (bool load_p, rtx reg_op,
>> + machine_mode mode) = 0;
>> +
>> + // Return alias check limit.
>> + // This is needed to avoid unbounded quadratic behaviour when
>> + // performing alias analysis.
>> + virtual int pair_mem_alias_check_limit () = 0;
>> +
>> + // Returns true if we should try to handle writeback opportunities
>
> Missing punctuation at the end of the sentence here.
>
Addressed in v6 of the patch.
>> + // WHICH parameter decides ALL or EXISTING writeback pairs.
>
> How about: "WHICH determines the kinds of writeback opportunities the
> caller is asking about."
>
Addressed in v6 of the patch.
>> + virtual bool handle_writeback_opportunities (enum writeback which) = 0 ;
>> +
>> + // Given BASE_MEM, the mem from the lower candidate access for a pair,
>> + // and LOAD_P (true if the access is a load), check if we should proceed
>> + // to form the pair given the target's code generation policy on
>> + // paired accesses.
>> + virtual bool pair_mem_ok_with_policy (rtx base_mem, bool load_p) = 0;
>> +
>> + // Generate the pattern for a paired access. PATS gives the patterns
>
Addressed in v6 of the patch.
> Nit: two spaces after '.'. Run your patch through
> contrib/check_GNU_style.py before submitting, please.
>
Addressed in v6 of the patch.
>> + // for the individual memory accesses (which by this point must share a
>> + // common base register). If WRITEBACK is non-NULL, then this rtx
>> + // describes the update to the base register that should be performed by
>> + // the resulting insn. LOAD_P is true iff the accesses are loads.
>> + virtual rtx gen_pair (rtx *pats, rtx writeback, bool load_p) = 0;
>> +
>> + // Return true if memory is paired access, given INSN and LOAD_P
>> + // is true for load insn and false for store insn.
>> + virtual bool pair_mem_insn_p (rtx_insn *, bool &) = 0;
>
> Since this is now a pure virtual, you can use parameter names in the
> prototype, then refer to them directly in the comment, so something
> like:
>
Addressed in v6 of the patch.
> // Return true if INSN is a paired memory access. If so, set LOAD_P to
> // true iff INSN is a load pair.
>
Addressed in v6 of the patch.
>> +
>> + // Return true if we should track loads.
>> + virtual bool track_loads_p ()
>> + {
>> + return true;
>> + }
>> +
>> + // Return true if we should track stores.
>> + virtual bool track_stores_p ()
>> + {
>> + return true;
>> + }
>> +
>> + // Return true if OFF is in range.
>
Addressed in v6 of the patch.
> Excess space after OFF. Sorry for missing this last time, but "in
> range" by itself isn't meaningful, how about "in range for a paired
> memory access" instead.
>
Addressed in v6 of the patch.
>> + virtual bool pair_mem_in_range_p (HOST_WIDE_INT off) = 0;
>
> Sorry for the nit, but I suggested last time renaming s/off/offset/.
> Let's do that, please.
>
Addressed in v6 of the patch.
>> +
>> + // Given a load/store pair insn in PATTERN, unpack the insn, storing
>> + // the register operands in REGS, and returning the mem. LOAD_P is true
>
> Nit: two spaces after '.'.
>
Addressed in v6 of the patch.
>> + // for load and false for store.
>
> Sorry for the nit, but I think the last sentence should say "LOAD_P is
> true for loads and false for stores." (i.e. plural loads/stores).
>
Addressed in v6 of the patch.
>> + virtual rtx destructure_pair (rtx regs[2], rtx pattern, bool load_p) = 0;
>> +
>> + // Given a pair mem in PAIR_MEM, register operands in REGS, and an rtx
>
> The name PAIR_MEM doesn't match the parameter name. One of them needs
> to change.
>
Addressed in v6 of the patch.
>> + // representing the effect of writeback on the base register in WB_EFFECT,
>> + // return an insn representing a writeback variant of this pair.
>> + // LOAD_P is true iff the pair is a load.
>> + // This is used when promoting existing non-writeback pairs to writeback
>> + // variants.
>> + virtual rtx gen_promote_writeback_pair (rtx wb_effect, rtx mem,
>> + rtx regs[2], bool load_p) = 0;
>> +
>> + void ldp_fusion_bb (bb_info *bb);
>> + inline insn_info *find_trailing_add (insn_info *insns[2],
>> + const insn_range_info &pair_range,
>> + int initial_writeback,
>> + rtx *writeback_effect,
>> + def_info **add_def,
>> + def_info *base_def,
>> + poly_int64 initial_offset,
>> + unsigned access_size);
>> + inline int get_viable_bases (insn_info *insns[2],
>> + vec<base_cand> &base_cands,
>> + rtx cand_mems[2],
>> + unsigned access_size,
>> + bool reversed);
>> + inline void do_alias_analysis (insn_info *alias_hazards[4],
>> + alias_walker *walkers[4],
>> + bool load_p);
>> + inline void try_promote_writeback (insn_info *insn, bool load_p);
>> + inline void run ();
>> + ~pair_fusion()
>
Addressed in v6 of the patch.
> Nit: space before '('. Again, contrib/check_GNU_style.py can help here.
>
>> + {
>> + if (crtl->ssa->perform_pending_updates ())
>> + cleanup_cfg (0);
>> +
>> + free_dominance_info (CDI_DOMINATORS);
>> +
>> + delete crtl->ssa;
>> + crtl->ssa = nullptr;
>> + }
>> +};
>> +
>> +// This is the main function to start the pass.
>> +void
>> +pair_fusion::run ()
>> +{
>> + if (!track_loads_p () && !track_stores_p ())
>> + return;
>> +
>> + for (auto bb : crtl->ssa->bbs ())
>> + ldp_fusion_bb (bb);
>> +}
>> +
>> +struct aarch64_pair_fusion : public pair_fusion
>> +{
>> + // Before RA, we use the modes, noting that stores of constant zero
>> + // operands use GPRs (even in non-integer modes). After RA, we use
>> + // the hard register numbers.
>
Addressed in v6 of the patch.
> Sorry for the very minor nit, but I think this comment would fit better
> inside the function body (above the return statement).
>
Addressed in v6 of the patch.
>> + bool fpsimd_op_p (rtx reg_op, machine_mode mem_mode,
>> + bool load_p) override final
>> + {
>> + return reload_completed
>> + ? (REG_P (reg_op) && FP_REGNUM_P (REGNO (reg_op)))
>> + : (GET_MODE_CLASS (mem_mode) != MODE_INT
>> + && (load_p || !aarch64_const_zero_rtx_p (reg_op)));
>> + }
>> +
>> + bool pair_mem_insn_p (rtx_insn *rti, bool &load_p) override final;
>> + bool pair_mem_ok_with_policy (rtx base_mem, bool load_p) override final
>> + {
>> + return aarch64_mem_ok_with_ldpstp_policy_model (base_mem,
>> + load_p,
>> + GET_MODE (base_mem));
>> + }
>
Addressed in v6 of the patch.
> Can we add blank lines between all of the inline member function
> implementations in this class, please? I did ask about that last time.
>
>> + bool pair_operand_mode_ok_p (machine_mode mode);
>
> Looks like you're still missing "override final" on all of these
> remaining overrides.
>
>> + rtx gen_pair (rtx *pats, rtx writeback, bool load_p);
>> + bool pair_reg_operand_ok_p (bool load_p, rtx reg_op,
>> + machine_mode mode)
>> + {
>> + return (load_p
>> + ? aarch64_ldp_reg_operand (reg_op, mode)
>> + : aarch64_stp_reg_operand (reg_op, mode));
>> + }
>> + int pair_mem_alias_check_limit ()
>> + {
>> + return aarch64_ldp_alias_check_limit;
>> + }
>> + bool handle_writeback_opportunities (enum writeback which)
>> + {
>> + if (which == writeback::ALL)
>> + return aarch64_ldp_writeback > 1;
>> + else
>> + return aarch64_ldp_writeback;
>> + }
>> + bool track_loads_p ()
>> + {
>> + return aarch64_tune_params.ldp_policy_model
>> + != AARCH64_LDP_STP_POLICY_NEVER;
>> + }
>> + bool track_stores_p ()
>> + {
>> + return aarch64_tune_params.stp_policy_model
>> + != AARCH64_LDP_STP_POLICY_NEVER;
>> + }
>> + bool pair_mem_in_range_p (HOST_WIDE_INT off)
>> + {
>> + return (off >= LDP_MIN_IMM && off <= LDP_MAX_IMM);
>> + }
>> + rtx gen_promote_writeback_pair (rtx wb_effect, rtx mem, rtx regs[2],
>> + bool load_p);
>> + rtx destructure_pair (rtx regs[2], rtx rti, bool load_p);
>> +};
>> +
>> // State used by the pass for a given basic block.
>> struct ldp_bb_info
>> {
>> @@ -159,9 +363,9 @@ struct ldp_bb_info
>> hash_map<def_hash, alt_base> canon_base_map;
>>
>> static const size_t obstack_alignment = sizeof (void *);
>> - bb_info *m_bb;
>>
>> - ldp_bb_info (bb_info *bb) : m_bb (bb), m_emitted_tombstone (false)
>> + ldp_bb_info (bb_info *bb, pair_fusion *d)
>> + : m_bb (bb), m_pass (d), m_emitted_tombstone (false)
>> {
>> obstack_specify_allocation (&m_obstack, OBSTACK_CHUNK_SIZE,
>> obstack_alignment, obstack_chunk_alloc,
>> @@ -181,37 +385,75 @@ struct ldp_bb_info
>> inline void track_access (insn_info *, bool load, rtx mem);
>> inline void transform ();
>> inline void cleanup_tombstones ();
>> + inline void merge_pairs (insn_list_t &, insn_list_t &,
>> + bool load_p, unsigned access_size);
>> + inline void transform_for_base (int load_size, access_group &group);
>> +
>> + inline bool try_fuse_pair (bool load_p, unsigned access_size,
>> + insn_info *i1, insn_info *i2);
>> +
>> + inline bool fuse_pair (bool load_p, unsigned access_size,
>> + int writeback,
>> + insn_info *i1, insn_info *i2,
>> + base_cand &base,
>> + const insn_range_info &move_range);
>> +
>> + inline void track_tombstone (int uid);
>
> You keep missing my review comments here. Why are you changing these
> member functions from private to public?
>
Addressed in v6 of the patch.
>>
>> private:
>> obstack m_obstack;
>> -
>
> Can we keep the blank lines here? They were there to logically group
> together the members related to tracking tombstones.
>
>> + bb_info *m_bb;
>> + pair_fusion *m_pass;
>> // State for keeping track of tombstone insns emitted for this BB.
>> bitmap_obstack m_bitmap_obstack;
>> bitmap_head m_tombstone_bitmap;
>> bool m_emitted_tombstone;
>> -
>> + template<typename Map> inline void traverse_base_map (Map &map);
>> + inline bool track_via_mem_expr (insn_info *, rtx mem, lfs_fields lfs);
>> inline splay_tree_node<access_record *> *node_alloc (access_record *);
>> +};
>
> What is the purpose of these changes? Why are you moving these
> function declarations around?
>
Addressed in v6 of the patch.
>>
>> - template<typename Map>
>> - inline void traverse_base_map (Map &map);
>> - inline void transform_for_base (int load_size, access_group &group);
>> -
>> - inline void merge_pairs (insn_list_t &, insn_list_t &,
>> - bool load_p, unsigned access_size);
>> -
>> - inline bool try_fuse_pair (bool load_p, unsigned access_size,
>> - insn_info *i1, insn_info *i2);
>> +bool
>> +aarch64_pair_fusion::pair_mem_insn_p (rtx_insn *rti,
>> + bool &load_p)
>
> No need for the line break here, the params should fit on a single line.
>
>> +{
>> + rtx pat = PATTERN (rti);
>> + if (GET_CODE (pat) == PARALLEL
>> + && XVECLEN (pat, 0) == 2)
>> + {
>> + const auto attr = get_attr_ldpstp (rti);
>> + if (attr == LDPSTP_NONE)
>> + return false;
>>
>> - inline bool fuse_pair (bool load_p, unsigned access_size,
>> - int writeback,
>> - insn_info *i1, insn_info *i2,
>> - base_cand &base,
>> - const insn_range_info &move_range);
>> + load_p = (attr == LDPSTP_LDP);
>> + gcc_checking_assert (load_p || attr == LDPSTP_STP);
>> + return true;
>> + }
>> + return false;
>> +}
>>
>> - inline void track_tombstone (int uid);
>> +rtx
>> +aarch64_pair_fusion::gen_pair (rtx *pats,
>> + rtx writeback,
>> + bool load_p)
>
Addressed in v6 of the patch.
> Likewise, the params should all fit on a single line.
>
>> +{
>> + rtx pair_pat;
>>
>> - inline bool track_via_mem_expr (insn_info *, rtx mem, lfs_fields lfs);
>> -};
>> + if (writeback)
>> + {
>> + auto patvec = gen_rtvec (3, writeback, pats[0], pats[1]);
>> + return gen_rtx_PARALLEL (VOIDmode, patvec);
>
> Excess space after return.
>
Addressed in v6 of the patch.
>> + }
>> + else if (load_p)
>> + return aarch64_gen_load_pair (XEXP (pats[0], 0),
>> + XEXP (pats[1], 0),
>> + XEXP (pats[0], 1));
>> + else
>> + return aarch64_gen_store_pair (XEXP (pats[0], 0),
>> + XEXP (pats[0], 1),
>> + XEXP (pats[1], 1));
>> + return pair_pat;
>> +}
>>
>> splay_tree_node<access_record *> *
>> ldp_bb_info::node_alloc (access_record *access)
>> @@ -312,8 +554,8 @@ any_post_modify_p (rtx x)
>>
>> // Return true if we should consider forming ldp/stp insns from memory
>> // accesses with operand mode MODE at this stage in compilation.
>> -static bool
>> -ldp_operand_mode_ok_p (machine_mode mode)
>> +bool
>> +aarch64_pair_fusion::pair_operand_mode_ok_p (machine_mode mode)
>> {
>> if (!aarch64_ldpstp_operand_mode_p (mode))
>> return false;
>> @@ -404,9 +646,10 @@ ldp_bb_info::track_via_mem_expr (insn_info *insn, rtx
>> mem, lfs_fields lfs)
>> const machine_mode mem_mode = GET_MODE (mem);
>> const HOST_WIDE_INT mem_size = GET_MODE_SIZE (mem_mode).to_constant ();
>>
>> - // Punt on misaligned offsets. LDP/STP instructions require offsets to
>> be a
>> - // multiple of the access size, and we believe that misaligned offsets on
>> - // MEM_EXPR bases are likely to lead to misaligned offsets w.r.t. RTL
>> bases.
>> + // Punt on misaligned offsets. Paired memory access instructions require
>> + // offsets to be a multiple of the access size, and we believe that
>> + // misaligned offsets on MEM_EXPR bases are likely to lead to misaligned
>> + // offsets w.r.t. RTL bases.
>> if (!multiple_p (offset, mem_size))
>> return false;
>>
>> @@ -430,10 +673,10 @@ ldp_bb_info::track_via_mem_expr (insn_info *insn, rtx
>> mem, lfs_fields lfs)
>> }
>>
>> // Main function to begin pair discovery. Given a memory access INSN,
>> -// determine whether it could be a candidate for fusing into an ldp/stp,
>> -// and if so, track it in the appropriate data structure for this basic
>> -// block. LOAD_P is true if the access is a load, and MEM is the mem
>> -// rtx that occurs in INSN.
>> +// determine whether it could be a candidate for fusing into a paired
>> +// access, and if so, track it in the appropriate data structure for
>> +// this basic block. LOAD_P is true if the access is a load, and MEM
>> +// is the mem rtx that occurs in INSN.
>> void
>> ldp_bb_info::track_access (insn_info *insn, bool load_p, rtx mem)
>> {
>> @@ -441,35 +684,24 @@ ldp_bb_info::track_access (insn_info *insn, bool
>> load_p, rtx mem)
>> if (MEM_VOLATILE_P (mem))
>> return;
>>
>> - // Ignore writeback accesses if the param says to do so.
>> - if (!aarch64_ldp_writeback
>> + // Ignore writeback accesses if the hook says to do so.
>> + if (!m_pass->handle_writeback_opportunities (writeback::EXISTING)
>> && GET_RTX_CLASS (GET_CODE (XEXP (mem, 0))) == RTX_AUTOINC)
>> return;
>>
>> const machine_mode mem_mode = GET_MODE (mem);
>> - if (!ldp_operand_mode_ok_p (mem_mode))
>> + if (!m_pass->pair_operand_mode_ok_p (mem_mode))
>> return;
>>
>> rtx reg_op = XEXP (PATTERN (insn->rtl ()), !load_p);
>>
>> - // Ignore the access if the register operand isn't suitable for ldp/stp.
>> - if (load_p
>> - ? !aarch64_ldp_reg_operand (reg_op, mem_mode)
>> - : !aarch64_stp_reg_operand (reg_op, mem_mode))
>> + if (!m_pass->pair_reg_operand_ok_p (load_p, reg_op, mem_mode))
>> return;
>>
>> // We want to segregate FP/SIMD accesses from GPR accesses.
>> - //
>> - // Before RA, we use the modes, noting that stores of constant zero
>> - // operands use GPRs (even in non-integer modes). After RA, we use
>> - // the hard register numbers.
>> - const bool fpsimd_op_p
>> - = reload_completed
>> - ? (REG_P (reg_op) && FP_REGNUM_P (REGNO (reg_op)))
>> - : (GET_MODE_CLASS (mem_mode) != MODE_INT
>> - && (load_p || !aarch64_const_zero_rtx_p (reg_op)));
>> + const bool fpsimd_op_p = m_pass->fpsimd_op_p (reg_op, mem_mode, load_p);
>>
>> - // Note ldp_operand_mode_ok_p already rejected VL modes.
>> + // Note pair_operand_mode_ok_p already rejected VL modes.
>> const HOST_WIDE_INT mem_size = GET_MODE_SIZE (mem_mode).to_constant ();
>> const lfs_fields lfs = { load_p, fpsimd_op_p, mem_size };
>>
>> @@ -498,8 +730,8 @@ ldp_bb_info::track_access (insn_info *insn, bool load_p,
>> rtx mem)
>> // elimination offset pre-RA, we should postpone forming pairs on such
>> // accesses until after RA.
>> //
>> - // As it stands, addresses with offsets in range for LDR but not
>> - // in range for LDP/STP are currently reloaded inefficiently,
>> + // As it stands, addresses in range for an individual load/store but not
>> + // for a paired access are currently reloaded inefficiently,
>> // ending up with a separate base register for each pair.
>> //
>> // In theory LRA should make use of
>> @@ -510,11 +742,11 @@ ldp_bb_info::track_access (insn_info *insn, bool
>> load_p, rtx mem)
>> // constraint; this early return means we never get to the code
>> // that calls targetm.legitimize_address_displacement.
>> //
>> - // So for now, it's better to punt when we can't be sure that the
>> - // offset is in range for LDP/STP. Out-of-range cases can then be
>> - // handled after RA by the out-of-range LDP/STP peepholes. Eventually, it
>> - // would be nice to handle known out-of-range opportunities in the
>> - // pass itself (for stack accesses, this would be in the post-RA pass).
>> + // It's better to punt when we can't be sure that the
>> + // offset is in range for paired access. On aarch64, Out-of-range cases
>> + // can then be handled after RA by the out-of-range PAIR MEM peepholes.
>
> No need to change "LDP/STP" to "PAIR MEM " here, now that you've
> qualified that sentence as being aarch64-specific.
>
Addressed in v6 of the patch.
>> + // Eventually, it would be nice to handle known out-of-range opportunities
>> + // in the pass itself (for stack accesses, this would be in the post-RA
>> pass).
>> if (!reload_completed
>> && (REGNO (base) == FRAME_POINTER_REGNUM
>> || REGNO (base) == ARG_POINTER_REGNUM))
>> @@ -565,8 +797,8 @@ ldp_bb_info::track_access (insn_info *insn, bool load_p,
>> rtx mem)
>> gcc_unreachable (); // Base defs should be unique.
>> }
>>
>> - // Punt on misaligned offsets. LDP/STP require offsets to be a multiple
>> of
>> - // the access size.
>> + // Punt on misaligned offsets. Paired memory accesses require offsets
>> + // to be a multiple of the access size.
>> if (!multiple_p (mem_off, mem_size))
>> return;
>>
>> @@ -1199,8 +1431,8 @@ extract_writebacks (bool load_p, rtx pats[2], int
>> changed)
>> // base register. If there is one, we choose the first such update after
>> // PAIR_DST that is still in the same BB as our pair. We return the new
>> def in
>> // *ADD_DEF and the resulting writeback effect in *WRITEBACK_EFFECT.
>> -static insn_info *
>> -find_trailing_add (insn_info *insns[2],
>> +insn_info *
>> +pair_fusion::find_trailing_add (insn_info *insns[2],
>> const insn_range_info &pair_range,
>> int initial_writeback,
>> rtx *writeback_effect,
>> @@ -1278,7 +1510,7 @@ find_trailing_add (insn_info *insns[2],
>>
>> off_hwi /= access_size;
>>
>> - if (off_hwi < LDP_MIN_IMM || off_hwi > LDP_MAX_IMM)
>> + if (!pair_mem_in_range_p (off_hwi))
>> return nullptr;
>>
>> auto dump_prefix = [&]()
>> @@ -1792,7 +2024,7 @@ ldp_bb_info::fuse_pair (bool load_p,
>> {
>> if (dump_file)
>> fprintf (dump_file,
>> - " ldp: i%d has wb but subsequent i%d has non-wb "
>> + " load pair: i%d has wb but subsequent i%d has non-wb "
>> "update of base (r%d), dropping wb\n",
>> insns[0]->uid (), insns[1]->uid (), base_regno);
>> gcc_assert (writeback_effect);
>> @@ -1815,7 +2047,7 @@ ldp_bb_info::fuse_pair (bool load_p,
>> }
>>
>> // If either of the original insns had writeback, but the resulting pair
>> insn
>> - // does not (can happen e.g. in the ldp edge case above, or if the
>> writeback
>> + // does not (can happen e.g. in the load pair edge case above, or if the
>> writeback
>
> Nit: long line here (comment needs re-wrapping).
>
Addressed in v6 of the patch.
>> // effects cancel out), then drop the def(s) of the base register as
>> // appropriate.
>> //
>> @@ -1834,7 +2066,7 @@ ldp_bb_info::fuse_pair (bool load_p,
>> // update of the base register and try and fold it in to make this into a
>> // writeback pair.
>> insn_info *trailing_add = nullptr;
>> - if (aarch64_ldp_writeback > 1
>> + if (m_pass->handle_writeback_opportunities (writeback::ALL)
>> && !writeback_effect
>> && (!load_p || (!refers_to_regno_p (base_regno, base_regno + 1,
>> XEXP (pats[0], 0), nullptr)
>> @@ -1842,7 +2074,7 @@ ldp_bb_info::fuse_pair (bool load_p,
>> XEXP (pats[1], 0), nullptr))))
>> {
>> def_info *add_def;
>> - trailing_add = find_trailing_add (insns, move_range, writeback,
>> + trailing_add = m_pass->find_trailing_add (insns, move_range,
>> writeback,
>> &writeback_effect,
>> &add_def, base.def, offsets[0],
>> access_size);
>
> Looks like the parameters need re-indenting here.
>
>> @@ -1855,35 +2087,19 @@ ldp_bb_info::fuse_pair (bool load_p,
>> }
>>
>> // Now that we know what base mem we're going to use, check if it's OK
>> - // with the ldp/stp policy.
>> + // with the pair mem policy.
>> rtx first_mem = XEXP (pats[0], load_p);
>> - if (!aarch64_mem_ok_with_ldpstp_policy_model (first_mem,
>> - load_p,
>> - GET_MODE (first_mem)))
>> + if (!m_pass->pair_mem_ok_with_policy (first_mem, load_p))
>> {
>> if (dump_file)
>> - fprintf (dump_file, "punting on pair (%d,%d), ldp/stp policy says no\n",
>> + fprintf (dump_file, "punting on pair (%d,%d), pair mem policy says
>> no\n",
>> i1->uid (), i2->uid ());
>> return false;
>> }
>>
>> rtx reg_notes = combine_reg_notes (first, second, load_p);
>>
>> - rtx pair_pat;
>> - if (writeback_effect)
>> - {
>> - auto patvec = gen_rtvec (3, writeback_effect, pats[0], pats[1]);
>> - pair_pat = gen_rtx_PARALLEL (VOIDmode, patvec);
>> - }
>> - else if (load_p)
>> - pair_pat = aarch64_gen_load_pair (XEXP (pats[0], 0),
>> - XEXP (pats[1], 0),
>> - XEXP (pats[0], 1));
>> - else
>> - pair_pat = aarch64_gen_store_pair (XEXP (pats[0], 0),
>> - XEXP (pats[0], 1),
>> - XEXP (pats[1], 1));
>> -
>> + rtx pair_pat = m_pass->gen_pair (pats, writeback_effect, load_p);
>> insn_change *pair_change = nullptr;
>> auto set_pair_pat = [pair_pat,reg_notes](insn_change *change) {
>> rtx_insn *rti = change->insn ()->rtl ();
>> @@ -2125,15 +2341,6 @@ load_modified_by_store_p (insn_info *load,
>> return false;
>> }
>>
>> -// Virtual base class for load/store walkers used in alias analysis.
>> -struct alias_walker
>> -{
>> - virtual bool conflict_p (int &budget) const = 0;
>> - virtual insn_info *insn () const = 0;
>> - virtual bool valid () const = 0;
>> - virtual void advance () = 0;
>> -};
>> -
>> // Implement some common functionality used by both store_walker
>> // and load_walker.
>> template<bool reverse>
>> @@ -2251,13 +2458,13 @@ public:
>> //
>> // We try to maintain the invariant that if a walker becomes invalid, we
>> // set its pointer to null.
>> -static void
>> -do_alias_analysis (insn_info *alias_hazards[4],
>> +void
>> +pair_fusion::do_alias_analysis (insn_info *alias_hazards[4],
>> alias_walker *walkers[4],
>> bool load_p)
>> {
>> const int n_walkers = 2 + (2 * !load_p);
>> - int budget = aarch64_ldp_alias_check_limit;
>> + int budget = pair_mem_alias_check_limit ();
>>
>> auto next_walker = [walkers,n_walkers](int current) -> int {
>> for (int j = 1; j <= n_walkers; j++)
>> @@ -2342,8 +2549,8 @@ do_alias_analysis (insn_info *alias_hazards[4],
>> //
>> // Returns an integer where bit (1 << i) is set if INSNS[i] uses writeback
>> // addressing.
>> -static int
>> -get_viable_bases (insn_info *insns[2],
>> +int
>> +pair_fusion::get_viable_bases (insn_info *insns[2],
>> vec<base_cand> &base_cands,
>> rtx cand_mems[2],
>> unsigned access_size,
>
Addressed in v6 of the patch.
> Indentation looks off here.
>
>> @@ -2389,7 +2596,7 @@ get_viable_bases (insn_info *insns[2],
>> if (!is_lower)
>> base_off--;
>>
>> - if (base_off < LDP_MIN_IMM || base_off > LDP_MAX_IMM)
>> + if (!pair_mem_in_range_p (base_off))
>> continue;
>>
>> use_info *use = find_access (insns[i]->uses (), REGNO (base));
>> @@ -2446,7 +2653,7 @@ get_viable_bases (insn_info *insns[2],
>> }
>>
>> // Given two adjacent memory accesses of the same size, I1 and I2, try
>> -// and see if we can merge them into a ldp or stp.
>> +// and see if we can merge them into a paired access.
>> //
>> // ACCESS_SIZE gives the (common) size of a single access, LOAD_P is true
>> // if the accesses are both loads, otherwise they are both stores.
>> @@ -2486,7 +2693,7 @@ ldp_bb_info::try_fuse_pair (bool load_p, unsigned
>> access_size,
>> {
>> if (dump_file)
>> fprintf (dump_file,
>> - "punting on ldp due to reg conflcits (%d,%d)\n",
>> + "punting on pair mem load due to reg conflcits (%d,%d)\n",
>
> Nit: double space after "load". I suppose just "load pair" would do here.
>
>> insns[0]->uid (), insns[1]->uid ());
>> return false;
>> }
>> @@ -2504,7 +2711,7 @@ ldp_bb_info::try_fuse_pair (bool load_p, unsigned
>> access_size,
>>
>> auto_vec<base_cand, 2> base_cands (2);
>>
>> - int writeback = get_viable_bases (insns, base_cands, cand_mems,
>> + int writeback = m_pass->get_viable_bases (insns, base_cands, cand_mems,
>> access_size, reversed);
>
> Indentation is wrong here.
>
Addressed in v6 of the patch.
>> if (base_cands.is_empty ())
>> {
>> @@ -2633,7 +2840,7 @@ ldp_bb_info::try_fuse_pair (bool load_p, unsigned
>> access_size,
>> walkers[1] = &backward_store_walker;
>>
>> if (load_p && (mem_defs[0] || mem_defs[1]))
>> - do_alias_analysis (alias_hazards, walkers, load_p);
>> + m_pass->do_alias_analysis (alias_hazards, walkers, load_p);
>> else
>> {
>> // We want to find any loads hanging off the first store.
>> @@ -2642,7 +2849,7 @@ ldp_bb_info::try_fuse_pair (bool load_p, unsigned
>> access_size,
>> load_walker<true> backward_load_walker (mem_defs[1], insns[1],
>> insns[0]);
>> walkers[2] = &forward_load_walker;
>> walkers[3] = &backward_load_walker;
>> - do_alias_analysis (alias_hazards, walkers, load_p);
>> + m_pass->do_alias_analysis (alias_hazards, walkers, load_p);
>> // Now consolidate hazards back down.
>> if (alias_hazards[2]
>> && (!alias_hazards[0] || (*alias_hazards[2] < *alias_hazards[0])))
>> @@ -2956,26 +3163,6 @@ ldp_bb_info::transform ()
>> traverse_base_map (def_map);
>> }
>>
>> -static void
>> -ldp_fusion_init ()
>> -{
>> - calculate_dominance_info (CDI_DOMINATORS);
>> - df_analyze ();
>> - crtl->ssa = new rtl_ssa::function_info (cfun);
>> -}
>> -
>> -static void
>> -ldp_fusion_destroy ()
>> -{
>> - if (crtl->ssa->perform_pending_updates ())
>> - cleanup_cfg (0);
>> -
>> - free_dominance_info (CDI_DOMINATORS);
>> -
>> - delete crtl->ssa;
>> - crtl->ssa = nullptr;
>> -}
>> -
>> // Given a load pair insn in PATTERN, unpack the insn, storing
>> // the registers in REGS and returning the mem.
>> static rtx
>> @@ -3015,16 +3202,19 @@ aarch64_destructure_store_pair (rtx regs[2], rtx
>> pattern)
>> return mem;
>> }
>>
>> -// Given a pair mem in PAIR_MEM, register operands in REGS, and an rtx
>> -// representing the effect of writeback on the base register in WB_EFFECT,
>> -// return an insn representing a writeback variant of this pair.
>> -// LOAD_P is true iff the pair is a load.
>> -//
>> -// This is used when promoting existing non-writeback pairs to writeback
>> -// variants.
>> -static rtx
>> -aarch64_gen_writeback_pair (rtx wb_effect, rtx pair_mem, rtx regs[2],
>> - bool load_p)
>> +rtx
>> +aarch64_pair_fusion::destructure_pair (rtx regs[2], rtx rti, bool load_p)
>> +{
>> + if (load_p)
>> + return aarch64_destructure_load_pair (regs, rti);
>> + else
>> + return aarch64_destructure_store_pair (regs, rti);
>> +}
>> +
>> +rtx
>> +aarch64_pair_fusion::gen_promote_writeback_pair (rtx wb_effect, rtx
>> pair_mem,
>> + rtx regs[2],
>> + bool load_p)
>> {
>> auto op_mode = aarch64_operand_mode_for_pair_mode (GET_MODE (pair_mem));
>>
>> @@ -3059,23 +3249,13 @@ aarch64_gen_writeback_pair (rtx wb_effect, rtx
>> pair_mem, rtx regs[2],
>> // Given an existing pair insn INSN, look for a trailing update of
>> // the base register which we can fold in to make this pair use
>> // a writeback addressing mode.
>> -static void
>> -try_promote_writeback (insn_info *insn)
>> +void
>> +pair_fusion::try_promote_writeback (insn_info *insn, bool load_p)
>> {
>> - auto rti = insn->rtl ();
>> - const auto attr = get_attr_ldpstp (rti);
>> - if (attr == LDPSTP_NONE)
>> - return;
>> -
>> - bool load_p = (attr == LDPSTP_LDP);
>> - gcc_checking_assert (load_p || attr == LDPSTP_STP);
>> -
>> rtx regs[2];
>> rtx mem = NULL_RTX;
>> - if (load_p)
>> - mem = aarch64_destructure_load_pair (regs, PATTERN (rti));
>> - else
>> - mem = aarch64_destructure_store_pair (regs, PATTERN (rti));
>> +
>> + mem = destructure_pair (regs, PATTERN (insn->rtl ()), load_p);
>
> Sorry for missing this before, but it's better just to have:
>
> rtx mem = destructure_pair (...);
>
> i.e. declare and initialize it on the same line.
>
Addressed in v6 of the patch.
>> gcc_checking_assert (MEM_P (mem));
>>
>> poly_int64 offset;
>> @@ -3112,9 +3292,10 @@ try_promote_writeback (insn_info *insn)
>> def_info *add_def;
>> const insn_range_info pair_range (insn);
>> insn_info *insns[2] = { nullptr, insn };
>> - insn_info *trailing_add = find_trailing_add (insns, pair_range, 0,
>> &wb_effect,
>> - &add_def, base_def, offset,
>> - access_size);
>> + insn_info *trailing_add
>> + = find_trailing_add (insns, pair_range, 0, &wb_effect,
>> + &add_def, base_def, offset,
>> + access_size);
>> if (!trailing_add)
>> return;
>>
>> @@ -3124,8 +3305,10 @@ try_promote_writeback (insn_info *insn)
>> insn_change del_change (trailing_add, insn_change::DELETE);
>> insn_change *changes[] = { &pair_change, &del_change };
>>
>> - rtx pair_pat = aarch64_gen_writeback_pair (wb_effect, mem, regs, load_p);
>> - validate_unshare_change (rti, &PATTERN (rti), pair_pat, true);
>> + rtx pair_pat = gen_promote_writeback_pair (wb_effect, mem, regs,
>> + load_p);
>
> The params should all fit on a single line here.
>
Addressed in v6 of the patch.
>> + validate_unshare_change (insn->rtl(), &PATTERN (insn->rtl()), pair_pat,
>
> Space before '(' in function calls (two occurrences here).
>
>> + true);
>>
>> // The pair must gain the def of the base register from the add.
>> pair_change.new_defs = insert_access (attempt,
>> @@ -3159,14 +3342,12 @@ try_promote_writeback (insn_info *insn)
>> // for load/store candidates. If running after RA, also try and promote
>> // non-writeback pairs to use writeback addressing. Then try to fuse
>> // candidates into pairs.
>> -void ldp_fusion_bb (bb_info *bb)
>> +void pair_fusion::ldp_fusion_bb (bb_info *bb)
>> {
>> - const bool track_loads
>> - = aarch64_tune_params.ldp_policy_model != AARCH64_LDP_STP_POLICY_NEVER;
>> - const bool track_stores
>> - = aarch64_tune_params.stp_policy_model != AARCH64_LDP_STP_POLICY_NEVER;
>> + const bool track_loads = track_loads_p ();
>> + const bool track_stores = track_stores_p ();
>>
>> - ldp_bb_info bb_state (bb);
>> + ldp_bb_info bb_state (bb, this);
>>
>> for (auto insn : bb->nondebug_insns ())
>> {
>> @@ -3176,11 +3357,11 @@ void ldp_fusion_bb (bb_info *bb)
>> continue;
>>
>> rtx pat = PATTERN (rti);
>> + bool load_p;
>> if (reload_completed
>> - && aarch64_ldp_writeback > 1
>> - && GET_CODE (pat) == PARALLEL
>> - && XVECLEN (pat, 0) == 2)
>> - try_promote_writeback (insn);
>> + && handle_writeback_opportunities (writeback::ALL)
>> + && pair_mem_insn_p (rti, load_p))
>> + try_promote_writeback (insn, load_p);
>>
>> if (GET_CODE (pat) != SET)
>> continue;
>> @@ -3195,16 +3376,6 @@ void ldp_fusion_bb (bb_info *bb)
>> bb_state.cleanup_tombstones ();
>> }
>>
>> -void ldp_fusion ()
>> -{
>> - ldp_fusion_init ();
>> -
>> - for (auto bb : crtl->ssa->bbs ())
>> - ldp_fusion_bb (bb);
>> -
>> - ldp_fusion_destroy ();
>> -}
>> -
>> namespace {
>>
>> const pass_data pass_data_ldp_fusion =
>> @@ -3234,14 +3405,6 @@ public:
>> if (!optimize || optimize_debug)
>> return false;
>>
>> - // If the tuning policy says never to form ldps or stps, don't run
>> - // the pass.
>> - if ((aarch64_tune_params.ldp_policy_model
>> - == AARCH64_LDP_STP_POLICY_NEVER)
>> - && (aarch64_tune_params.stp_policy_model
>> - == AARCH64_LDP_STP_POLICY_NEVER))
>> - return false;
>> -
>> if (reload_completed)
>> return flag_aarch64_late_ldp_fusion;
>> else
>> @@ -3250,7 +3413,8 @@ public:
>>
>> unsigned execute (function *) final override
>> {
>> - ldp_fusion ();
>> + aarch64_pair_fusion pass;
>> + pass.run ();
>> return 0;
>> }
>> };
>> --
>> 2.39.3
>>
>
> Thanks,
> Alex
Thanks & Regards
Ajit
