new sign/zero extension elimination pass
Tom de Vries
Tom_deVries@mentor.com
Thu Jul 12 09:21:00 GMT 2012
Kenneth,
I see I replied to your original message that had the wrong CC, I'm now CC-ing
gcc-patches@gcc.gnu.org.
Thanks,
- Tom
On 12/07/12 11:05, Tom de Vries wrote:
> On 12/07/12 03:39, Kenneth Zadeck wrote:
>> Tom,
>>
>> I have a problem with the approach that you have taken here. I believe
>> that this could be a very useful addition to gcc so I am in general very
>> supportive, but i think you are missing an important case.
>>
>> My problem is that it the pass does not actually look at the target and
>> make any decisions based on that target.
>>
>> for instance, we have a llp64 target. As with many targets, the target
>> has a rich set of compare and branch instructions. In particular, it
>> can do both 32 and 64 bit comparisons. We see that many of the
>> upstream optimizations that take int (SI mode) index variables generate
>> extension operations before doing 64 bit compare and branch
>> instructions, even though there are 32 bit comparison and branches on
>> the machine. There are a lot of machines that can do more than one
>> size of comparison.
>>
> This optimization pass, as it is currently written will not remove those
>> extensions because it believes that the length of the destination is the
>> "final answer" unless it is wrapped in an explicit truncation.
>> Instead it needs to ask the port if there is a shorted compare and
>> branch instruction that does not cost more. in that case, those
>> instructions should be rewritten to use the shorted compare and branch.
>>
>> There are many operations other than compare and branch where the pass
>> should be asking "can i shorten the target for free and therefore get
>> rid of the extension?"
>
> Kenneth,
>
> I'm not sure I understand the optimization you're talking about, in particular
> I'm confused about whether the branch range of the 32-bit and 64-bit comparison
> is the same.
>
> Assuming it's the same, my understanding is that you're talking about an example
> like this:
> ...
> (insn (set (reg:DI 5)
> (zero_extend:DI (reg:SI 4))))
>
> (jump_insn (set (pc)
> (if_then_else (eq (reg:DI 5)
> (const_int 0))
> (label_ref:DI 62)
> (pc))))
>
> ->
>
> (jump_insn (set (pc)
> (if_then_else (eq (reg:SI 4)
> (const_int 0))
> (label_ref:DI 62)
> (pc))))
>
> ...
> I would expect combine to optimize this.
>
> In case I got the example all backwards or it is a too simple one, please
> provide an rtl example that illustrates the optimization.
>
> Thanks,
> - Tom
>
>
>> right shifts, rotates, and stores are not in
>> this class, but left shifts are as are all comparisons, compare and
>> branches, conditional moves. There may even be machines that have this
>> for divide, but i do not know of any off the top of my head.
>>
>> What i am suggesting moves this pass into the target specific set of
>> optimizations rather than target independent set, but at where this pass
>> is to be put this is completely appropriate. Any dest instruction
>> where all of the operands have been extended should be checked to see if
>> it was really necessary to use the longer form before doing the
>> propagation pass.
>>
>> kenny
>>
>>
>> On 07/11/2012 06:30 AM, Tom de Vries wrote:
>>> On 13/11/10 10:50, Eric Botcazou wrote:
>>>>> I profiled the pass on spec2000:
>>>>>
>>>>> -mabi=32 -mabi=64
>>>>> ee-pass (usr time): 0.70 1.16
>>>>> total (usr time): 919.30 879.26
>>>>> ee-pass (%): 0.08 0.13
>>>>>
>>>>> The pass takes 0.13% or less of the total usr runtime.
>>>> For how many hits? What are the numbers with --param ee-max-propagate=0?
>>>>
>>>>> Is it necessary to improve the runtime of this pass?
>>>> I've already given my opinion about the implementation. The other passes in
>>>> the compiler try hard not to rescan everything when a single bit changes; as
>>>> currently written, yours doesn't.
>>>>
>>> Eric,
>>>
>>> I've done the following:
>>> - refactored the pass such that it now scans at most twice over all
>>> instructions.
>>> - updated the patch to be applicable to current trunk
>>> - updated the motivating example to a more applicable one (as discussed in
>>> this thread), and added that one as test-case.
>>> - added a part in the header comment illustrating the working of the pass
>>> on the motivating example.
>>>
>>> bootstrapped and reg-tested on x86_64 and i686.
>>>
>>> build and reg-tested on mips, mips64, and arm.
>>>
>>> OK for trunk?
>>>
>>> Thanks,
>>> - Tom
>>>
>>> 2012-07-10 Tom de Vries <tom@codesourcery.com>
>>>
>>> * ee.c: New file.
>>> * tree-pass.h (pass_ee): Declare.
>>> * opts.c ( default_options_table): Set flag_ee at -O2.
>>> * timevar.def (TV_EE): New timevar.
>>> * common.opt (fextension-elimination): New option.
>>> * Makefile.in (ee.o): New rule.
>>> * passes.c (pass_ee): Add it.
>>>
>>> * gcc.dg/extend-1.c: New test.
>>> * gcc.dg/extend-2.c: Same.
>>> * gcc.dg/extend-2-64.c: Same.
>>> * gcc.dg/extend-3.c: Same.
>>> * gcc.dg/extend-4.c: Same.
>>> * gcc.dg/extend-5.c: Same.
>>> * gcc.target/mips/octeon-bbit-2.c: Make test more robust.
>>> Index: gcc/tree-pass.h
>>> ===================================================================
>>> --- gcc/tree-pass.h (revision 189409)
>>> +++ gcc/tree-pass.h (working copy)
>>> @@ -483,6 +483,7 @@ extern struct gimple_opt_pass pass_fixup
>>>
>>> extern struct rtl_opt_pass pass_expand;
>>> extern struct rtl_opt_pass pass_instantiate_virtual_regs;
>>> +extern struct rtl_opt_pass pass_ee;
>>> extern struct rtl_opt_pass pass_rtl_fwprop;
>>> extern struct rtl_opt_pass pass_rtl_fwprop_addr;
>>> extern struct rtl_opt_pass pass_jump;
>>> Index: gcc/testsuite/gcc.target/mips/octeon-bbit-2.c
>>> ===================================================================
>>> --- gcc/testsuite/gcc.target/mips/octeon-bbit-2.c (revision 189409)
>>> +++ gcc/testsuite/gcc.target/mips/octeon-bbit-2.c (working copy)
>>> @@ -5,19 +5,19 @@
>>> /* { dg-final { scan-assembler "\tbnel\t" } } */
>>> /* { dg-final { scan-assembler-not "\tbne\t" } } */
>>>
>>> -NOMIPS16 int
>>> -f (int n, int i)
>>> +NOMIPS16 long int
>>> +f (long int n, long int i)
>>> {
>>> - int s = 0;
>>> + long int s = 0;
>>> for (; i & 1; i++)
>>> s += i;
>>> return s;
>>> }
>>>
>>> -NOMIPS16 int
>>> -g (int n, int i)
>>> +NOMIPS16 long int
>>> +g (long int n, long int i)
>>> {
>>> - int s = 0;
>>> + long int s = 0;
>>> for (i = 0; i < n; i++)
>>> s += i;
>>> return s;
>>> Index: gcc/testsuite/gcc.dg/extend-4.c
>>> ===================================================================
>>> --- /dev/null (new file)
>>> +++ gcc/testsuite/gcc.dg/extend-4.c (revision 0)
>>> @@ -0,0 +1,16 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-O2 -fdump-rtl-ee" } */
>>> +
>>> +unsigned char f(unsigned int a, int c)
>>> +{
>>> + unsigned int b = a;
>>> + if (c)
>>> + b = a & 0x10ff;
>>> + return b;
>>> +}
>>> +
>>> +/* { dg-final { scan-rtl-dump-times "_extend:" 1 "ee" { target mips*-*-* } } } */
>>> +/* { dg-final { scan-rtl-dump-times "and:" 0 "ee" { target mips*-*-* } } } */
>>> +/* { dg-final { scan-rtl-dump "redundant extension \[0-9\]+ removed" "ee" { target mips*-*-* } } } */
>>> +/* { dg-final { cleanup-rtl-dump "ee" } } */
>>> +
>>> Index: gcc/testsuite/gcc.dg/extend-1.c
>>> ===================================================================
>>> --- /dev/null (new file)
>>> +++ gcc/testsuite/gcc.dg/extend-1.c (revision 0)
>>> @@ -0,0 +1,13 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-O2 -fdump-rtl-ee" } */
>>> +
>>> +void f(unsigned char * p, short s, int c, int *z)
>>> +{
>>> + if (c)
>>> + *z = 0;
>>> + *p ^= (unsigned char)s;
>>> +}
>>> +
>>> +/* { dg-final { scan-rtl-dump-times "sign_extend:" 0 "ee" { target mips*-*-* } } } */
>>> +/* { dg-final { scan-rtl-dump-times "redundant extension \[0-9\]+ replaced" 1 "ee" { target mips*-*-* } } } */
>>> +/* { dg-final { cleanup-rtl-dump "ee" } } */
>>> Index: gcc/testsuite/gcc.dg/extend-5.c
>>> ===================================================================
>>> --- /dev/null (new file)
>>> +++ gcc/testsuite/gcc.dg/extend-5.c (revision 0)
>>> @@ -0,0 +1,13 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-O2 -fdump-rtl-ee" } */
>>> +
>>> +void f (short d[2][2])
>>> +{
>>> + int d0 = d[0][0] + d[0][1];
>>> + int d1 = d[1][0] + d[1][1];
>>> + d[0][0] = d0 + d1;
>>> + d[0][1] = d0 - d1;
>>> +}
>>> +
>>> +/* { dg-final { scan-rtl-dump-times "redundant extension \[0-9\]+ replaced" 2 "ee" { target mips*-*-* } } } */
>>> +/* { dg-final { cleanup-rtl-dump "ee" } } */
>>> Index: gcc/testsuite/gcc.dg/extend-2.c
>>> ===================================================================
>>> --- /dev/null (new file)
>>> +++ gcc/testsuite/gcc.dg/extend-2.c (revision 0)
>>> @@ -0,0 +1,20 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-O2 -fdump-rtl-ee" } */
>>> +/* { dg-require-effective-target ilp32 } */
>>> +
>>> +void f(unsigned char * p, short *s, int c)
>>> +{
>>> + short or = 0;
>>> + while (c)
>>> + {
>>> + or = or | s[c];
>>> + c --;
>>> + }
>>> + *p = (unsigned char)or;
>>> +}
>>> +
>>> +/* { dg-final { scan-rtl-dump-times "zero_extend" 0 "ee" { target mips*-*-* } } } */
>>> +/* { dg-final { scan-rtl-dump-times "sign_extend" 0 "ee" { target mips*-*-* } } } */
>>> +/* { dg-final { scan-rtl-dump-times "redundant extension \[0-9\]+ replaced" 2 "ee" { target mips*-*-* } } } */
>>> +/* { dg-final { cleanup-rtl-dump "ee" } } */
>>> +
>>> Index: gcc/testsuite/gcc.dg/extend-2-64.c
>>> ===================================================================
>>> --- /dev/null (new file)
>>> +++ gcc/testsuite/gcc.dg/extend-2-64.c (revision 0)
>>> @@ -0,0 +1,20 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-O2 -fdump-rtl-ee -mabi=64" } */
>>> +/* { dg-require-effective-target mips64 } */
>>> +
>>> +void f(unsigned char * p, short *s, int c)
>>> +{
>>> + short or = 0;
>>> + while (c)
>>> + {
>>> + or = or | s[c];
>>> + c --;
>>> + }
>>> + *p = (unsigned char)or;
>>> +}
>>> +
>>> +/* { dg-final { scan-rtl-dump-times "zero_extend:" 0 "ee" { target mips*-*-* } } } */
>>> +/* { dg-final { scan-rtl-dump-times "sign_extend:" 1 "ee" { target mips*-*-* } } } */
>>> +/* { dg-final { scan-rtl-dump-times "redundant extension \[0-9\]+ replaced" 2 "ee" { target mips*-*-* } } } */
>>> +/* { dg-final { cleanup-rtl-dump "ee" } } */
>>> +
>>> Index: gcc/testsuite/gcc.dg/extend-3.c
>>> ===================================================================
>>> --- /dev/null (new file)
>>> +++ gcc/testsuite/gcc.dg/extend-3.c (revision 0)
>>> @@ -0,0 +1,13 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-O2 -fdump-rtl-ee -mabi=64" } */
>>> +/* { dg-require-effective-target mips64 } */
>>> +
>>> +unsigned int f(unsigned char byte)
>>> +{
>>> + return byte << 25;
>>> +}
>>> +
>>> +/* { dg-final { scan-rtl-dump-times "zero_extend:" 0 "ee" { target mips*-*-* } } } */
>>> +/* { dg-final { scan-rtl-dump "redundant extension \[0-9\]+ replaced" "ee" } } */
>>> +/* { dg-final { cleanup-rtl-dump "ee" } } */
>>> +
>>> Index: gcc/opts.c
>>> ===================================================================
>>> --- gcc/opts.c (revision 189409)
>>> +++ gcc/opts.c (working copy)
>>> @@ -490,6 +490,7 @@ static const struct default_options defa
>>> { OPT_LEVELS_2_PLUS, OPT_ftree_tail_merge, NULL, 1 },
>>> { OPT_LEVELS_2_PLUS_SPEED_ONLY, OPT_foptimize_strlen, NULL, 1 },
>>> { OPT_LEVELS_2_PLUS, OPT_fhoist_adjacent_loads, NULL, 1 },
>>> + { OPT_LEVELS_2_PLUS, OPT_fextension_elimination, NULL, 1 },
>>>
>>> /* -O3 optimizations. */
>>> { OPT_LEVELS_3_PLUS, OPT_ftree_loop_distribute_patterns, NULL, 1 },
>>> Index: gcc/timevar.def
>>> ===================================================================
>>> --- gcc/timevar.def (revision 189409)
>>> +++ gcc/timevar.def (working copy)
>>> @@ -201,6 +201,7 @@ DEFTIMEVAR (TV_POST_EXPAND , "post
>>> DEFTIMEVAR (TV_VARCONST , "varconst")
>>> DEFTIMEVAR (TV_LOWER_SUBREG , "lower subreg")
>>> DEFTIMEVAR (TV_JUMP , "jump")
>>> +DEFTIMEVAR (TV_EE , "extension elimination")
>>> DEFTIMEVAR (TV_FWPROP , "forward prop")
>>> DEFTIMEVAR (TV_CSE , "CSE")
>>> DEFTIMEVAR (TV_DCE , "dead code elimination")
>>> Index: gcc/ee.c
>>> ===================================================================
>>> --- /dev/null (new file)
>>> +++ gcc/ee.c (revision 0)
>>> @@ -0,0 +1,1190 @@
>>> +/* Redundant extension elimination.
>>> + Copyright (C) 2010, 2011, 2012 Free Software Foundation, Inc.
>>> + Contributed by Tom de Vries (tom@codesourcery.com)
>>> +
>>> +This file is part of GCC.
>>> +
>>> +GCC is free software; you can redistribute it and/or modify it under
>>> +the terms of the GNU General Public License as published by the Free
>>> +Software Foundation; either version 3, or (at your option) any later
>>> +version.
>>> +
>>> +GCC is distributed in the hope that it will be useful, but WITHOUT ANY
>>> +WARRANTY; without even the implied warranty of MERCHANTABILITY or
>>> +FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
>>> +for more details.
>>> +
>>> +You should have received a copy of the GNU General Public License
>>> +along with GCC; see the file COPYING3. If not see
>>> +<http://www.gnu.org/licenses/>. */
>>> +
>>> +/*
>>> +
>>> + MOTIVATING EXAMPLE
>>> +
>>> + The motivating example for this pass is the example from PR 40893:
>>> +
>>> + void f (short d[2][2])
>>> + {
>>> + int d0 = d[0][0] + d[0][1];
>>> + int d1 = d[1][0] + d[1][1];
>>> + d[0][0] = d0 + d1;
>>> + d[0][1] = d0 - d1;
>>> + }
>>> +
>>> + For MIPS, compilation results in the following insns.
>>> +
>>> + (set (reg:SI 204)
>>> + (zero_extend:SI (subreg:HI (reg:SI 213) 2)))
>>> +
>>> + (set (reg:SI 205)
>>> + (zero_extend:SI (subreg:HI (reg:SI 216 [ d1 ]) 2)))
>>> +
>>> + (set (reg:SI 217)
>>> + (plus:SI (reg:SI 205)
>>> + (reg:SI 204)))
>>> +
>>> + (set (reg:SI 218)
>>> + (minus:SI (reg:SI 204)
>>> + (reg:SI 205)))
>>> +
>>> + (set (mem:HI (reg/v/f:SI 210))
>>> + (subreg:HI (reg:SI 217) 2))
>>> +
>>> + (set (mem:HI (plus:SI (reg/v/f:SI 210)
>>> + (const_int 2 [0x2])))
>>> + (subreg:HI (reg:SI 218) 2))
>>> +
>>> +
>>> + The pseudos 217 and 218 only use the lower half of pseudos 217 and 218, and
>>> + are the only uses. And the plus and minus operators belong to the class of
>>> + operators where a bit in the result is only influenced by same-or-less
>>> + significant bitss in the operands, so the plus and minus insns only use the
>>> + lower halves of pseudos 204 and 205. Those are also the only uses of pseudos
>>> + 204 and 205, so the zero_extends are redundant.
>>> +
>>> +
>>> + INTENDED EFFECT
>>> +
>>> + This pass works by removing sign/zero-extensions, or replacing them with
>>> + regcopies. The idea there is that the regcopy might be eliminated by a later
>>> + pass. In case the regcopy cannot be eliminated, it might at least be cheaper
>>> + than the extension.
>>> +
>>> +
>>> + IMPLEMENTATION
>>> +
>>> + The pass scans at most two times over all instructions.
>>> +
>>> + The first scan collects all extensions. If there are no extensions, we're
>>> + done.
>>> +
>>> + The second scan registers all uses of a reg in the biggest_use array.
>>> + Additionally, it registers how the use size of a pseudo is propagated to the
>>> + operands of the insns defining the pseudo.
>>> +
>>> + The biggest_use array now contains the size in bits of the biggest use
>>> + of each reg, which allows us to find redundant extensions.
>>> +
>>> + If there are still non-redundant extensions left, we use the propagation
>>> + information in an iterative fashion to improve the biggest_use array, after
>>> + which we may find more redundant extensions.
>>> +
>>> + Finally, redundant extensions are deleted or replaced.
>>> +
>>> + In case that the src and dest reg of the replacement are not of the same size,
>>> + we do not replace with a normal regcopy, but with a truncate or with the copy
>>> + of a paradoxical subreg instead.
>>> +
>>> +
>>> + ILLUSTRATION OF PASS
>>> +
>>> + The dump of the pass shows us how the pass works on the motivating example.
>>> +
>>> + We find the 2 extensions:
>>> + found extension with preserved size 16 defining reg 204
>>> + found extension with preserved size 16 defining reg 205
>>> +
>>> + We calculate the biggests uses of a register:
>>> + biggest_use
>>> + reg 204: size 32
>>> + reg 205: size 32
>>> + reg 217: size 16
>>> + reg 218: size 16
>>> +
>>> + We propagate the biggest uses where possible:
>>> + propagations
>>> + 205: 32 -> 16
>>> + 204: 32 -> 16
>>> + 214: 32 -> 16
>>> + 215: 32 -> 16
>>> +
>>> + We conclude that the extensions are redundant:
>>> + found redundant extension with preserved size 16 defining reg 205
>>> + found redundant extension with preserved size 16 defining reg 204
>>> +
>>> + And we replace them with regcopies:
>>> + (set (reg:SI 204)
>>> + (reg:SI 213))
>>> +
>>> + (set (reg:SI 205)
>>> + (reg:SI 216))
>>> +
>>> +
>>> + LIMITATIONS
>>> +
>>> + The scope of the analysis is limited to an extension and its uses. The other
>>> + type of analysis (related to the defs of the operand of an extension) is not
>>> + done.
>>> +
>>> + Furthermore, we do the analysis of biggest use per reg. So when determining
>>> + whether an extension is redundant, we take all uses of a dest reg into
>>> + account, also the ones that are not uses of the extension.
>>> + The consideration is that using use-def chains will give a more precise
>>> + analysis, but is much more expensive in terms of runtime. */
>>> +
>>> +#include "config.h"
>>> +#include "system.h"
>>> +#include "coretypes.h"
>>> +#include "tm.h"
>>> +#include "rtl.h"
>>> +#include "tree.h"
>>> +#include "tm_p.h"
>>> +#include "flags.h"
>>> +#include "regs.h"
>>> +#include "hard-reg-set.h"
>>> +#include "basic-block.h"
>>> +#include "insn-config.h"
>>> +#include "function.h"
>>> +#include "expr.h"
>>> +#include "insn-attr.h"
>>> +#include "recog.h"
>>> +#include "toplev.h"
>>> +#include "target.h"
>>> +#include "timevar.h"
>>> +#include "optabs.h"
>>> +#include "insn-codes.h"
>>> +#include "rtlhooks-def.h"
>>> +#include "output.h"
>>> +#include "params.h"
>>> +#include "timevar.h"
>>> +#include "tree-pass.h"
>>> +#include "cgraph.h"
>>> +#include "vec.h"
>>> +
>>> +#define SKIP_REG (-1)
>>> +#define NONE (-1)
>>> +
>>> +/* Number of registers at start of pass. */
>>> +
>>> +static int n_regs;
>>> +
>>> +/* Array to register the biggest use of a reg, in bits. */
>>> +
>>> +static int *biggest_use;
>>> +
>>> +/* Array to register the promoted subregs. */
>>> +
>>> +static VEC (rtx,heap) **promoted_subreg;
>>> +
>>> +/* Array to register for a reg what the last propagated size is. */
>>> +
>>> +static int *propagated_size;
>>> +
>>> +typedef struct use
>>> +{
>>> + int regno;
>>> + int size;
>>> + int offset;
>>> + rtx *use;
>>> +} use_type;
>>> +
>>> +DEF_VEC_O(use_type);
>>> +DEF_VEC_ALLOC_O(use_type,heap);
>>> +
>>> +/* Vector to register the uses. */
>>> +
>>> +static VEC (use_type,heap) **uses;
>>> +
>>> +typedef struct prop
>>> +{
>>> + rtx set;
>>> + int uses_regno;
>>> + int uses_index;
>>> +} prop_type;
>>> +
>>> +DEF_VEC_O(prop_type);
>>> +DEF_VEC_ALLOC_O(prop_type,heap);
>>> +
>>> +/* Vector to register the propagations. */
>>> +
>>> +static VEC (prop_type,heap) **props;
>>> +
>>> +/* Work list for propragation. */
>>> +
>>> +static VEC (int,heap) *wl;
>>> +
>>> +/* Array to register what regs are in the work list. */
>>> +
>>> +static bool *in_wl;
>>> +
>>> +/* Vector that contains the extensions in the function. */
>>> +
>>> +static VEC (rtx,heap) *extensions;
>>> +
>>> +/* Vector that contains the extensions in the function that are going to be
>>> + removed or replaced. */
>>> +
>>> +static VEC (rtx,heap) *redundant_extensions;
>>> +
>>> +/* Forward declaration. */
>>> +
>>> +static void note_use (rtx *x, void *data);
>>> +static bool skip_reg_p (int regno);
>>> +static void register_prop (rtx set, use_type *use);
>>> +
>>> +/* Check whether SUBREG is a promoted subreg. */
>>> +
>>> +static bool
>>> +promoted_subreg_p (rtx subreg)
>>> +{
>>> + return (GET_CODE (subreg) == SUBREG
>>> + && SUBREG_PROMOTED_VAR_P (subreg));
>>> +}
>>> +
>>> +/* Check whether SUBREG is a promoted subreg for which we cannot reset the
>>> + promotion. */
>>> +
>>> +static bool
>>> +fixed_promoted_subreg_p (rtx subreg)
>>> +{
>>> + int mre;
>>> +
>>> + if (!promoted_subreg_p (subreg))
>>> + return false;
>>> +
>>> + mre = targetm.mode_rep_extended (GET_MODE (subreg),
>>> + GET_MODE (SUBREG_REG (subreg)));
>>> + return mre != UNKNOWN;
>>> +}
>>> +
>>> +/* Attempt to return the size, reg number and offset of USE in SIZE, REGNO and
>>> + OFFSET. Return true if successful. */
>>> +
>>> +static bool
>>> +reg_use_p (rtx use, int *size, unsigned int *regno, int *offset)
>>> +{
>>> + rtx reg;
>>> +
>>> + if (REG_P (use))
>>> + {
>>> + *regno = REGNO (use);
>>> + *offset = 0;
>>> + *size = GET_MODE_BITSIZE (GET_MODE (use));
>>> + return true;
>>> + }
>>> + else if (GET_CODE (use) == SUBREG)
>>> + {
>>> + reg = SUBREG_REG (use);
>>> +
>>> + if (!REG_P (reg))
>>> + return false;
>>> +
>>> + *regno = REGNO (reg);
>>> +
>>> + if (paradoxical_subreg_p (use) || fixed_promoted_subreg_p (use))
>>> + {
>>> + *offset = 0;
>>> + *size = GET_MODE_BITSIZE (GET_MODE (reg));
>>> + }
>>> + else
>>> + {
>>> + *offset = subreg_lsb (use);
>>> + *size = *offset + GET_MODE_BITSIZE (GET_MODE (use));
>>> + }
>>> +
>>> + return true;
>>> + }
>>> +
>>> + return false;
>>> +}
>>> +
>>> +/* Create a new empty entry in the uses[REGNO] vector. */
>>> +
>>> +static use_type *
>>> +new_use (unsigned int regno)
>>> +{
>>> + if (uses[regno] == NULL)
>>> + uses[regno] = VEC_alloc (use_type, heap, 4);
>>> +
>>> + VEC_safe_push (use_type, heap, uses[regno], NULL);
>>> +
>>> + return VEC_last (use_type, uses[regno]);
>>> +}
>>> +
>>> +/* Register a USE of reg REGNO with SIZE and OFFSET. */
>>> +
>>> +static use_type *
>>> +register_use (int size, unsigned int regno, int offset, rtx *use)
>>> +{
>>> + int *current;
>>> + use_type *p;
>>> +
>>> + gcc_assert (size >= 0);
>>> + gcc_assert (regno < (unsigned int)n_regs);
>>> +
>>> + if (skip_reg_p (regno))
>>> + return NULL;
>>> +
>>> + p = new_use (regno);
>>> + p->regno = regno;
>>> + p->size = size;
>>> + p->offset = offset;
>>> + p->use = use;
>>> +
>>> + /* Update the bigest use. */
>>> + current = &biggest_use[regno];
>>> + *current = MAX (*current, size);
>>> +
>>> + return p;
>>> +}
>>> +
>>> +/* Handle embedded uses in USE, which is a part of PATTERN. */
>>> +
>>> +static void
>>> +note_embedded_uses (rtx use, rtx pattern)
>>> +{
>>> + const char *format_ptr;
>>> + int i, j;
>>> +
>>> + format_ptr = GET_RTX_FORMAT (GET_CODE (use));
>>> + for (i = 0; i < GET_RTX_LENGTH (GET_CODE (use)); i++)
>>> + if (format_ptr[i] == 'e')
>>> + note_use (&XEXP (use, i), pattern);
>>> + else if (format_ptr[i] == 'E')
>>> + for (j = 0; j < XVECLEN (use, i); j++)
>>> + note_use (&XVECEXP (use, i, j), pattern);
>>> +}
>>> +
>>> +/* Get the set in PATTERN that has USE as its src operand. */
>>> +
>>> +static rtx
>>> +get_set (rtx use, rtx pattern)
>>> +{
>>> + rtx sub;
>>> + int i;
>>> +
>>> + if (GET_CODE (pattern) == SET && SET_SRC (pattern) == use)
>>> + return pattern;
>>> +
>>> + if (GET_CODE (pattern) == PARALLEL)
>>> + for (i = 0; i < XVECLEN (pattern, 0); ++i)
>>> + {
>>> + sub = XVECEXP (pattern, 0, i);
>>> + if (GET_CODE (sub) == SET && SET_SRC (sub) == use)
>>> + return sub;
>>> + }
>>> +
>>> + return NULL_RTX;
>>> +}
>>> +
>>> +/* Handle a restricted op USE with NR_OPERANDS. USE is a part of SET, which is
>>> + a part of PATTERN. In this context restricted means that a bit in
>>> + an operand influences only the same bit or more significant bits in the
>>> + result. The bitwise ops are a subclass, but PLUS is one as well. */
>>> +
>>> +static void
>>> +note_restricted_op_use (rtx set, rtx use, unsigned int nr_operands, rtx pattern)
>>> +{
>>> + unsigned int i, smallest;
>>> + int operand_size[2];
>>> + int operand_offset[2];
>>> + int used_size;
>>> + unsigned int operand_regno[2];
>>> + bool operand_reg[2];
>>> + bool operand_ignore[2];
>>> + use_type *p;
>>> +
>>> + /* Init operand_reg, operand_size, operand_regno and operand_ignore. */
>>> + for (i = 0; i < nr_operands; ++i)
>>> + {
>>> + operand_reg[i] = reg_use_p (XEXP (use, i), &operand_size[i],
>>> + &operand_regno[i], &operand_offset[i]);
>>> + operand_ignore[i] = false;
>>> + }
>>> +
>>> + /* Handle case of reg and-masked with const. */
>>> + if (GET_CODE (use) == AND && CONST_INT_P (XEXP (use, 1)) && operand_reg[0])
>>> + {
>>> + used_size =
>>> + HOST_BITS_PER_WIDE_INT - clz_hwi (UINTVAL (XEXP (use, 1)));
>>> + operand_size[0] = MIN (operand_size[0], used_size);
>>> + }
>>> +
>>> + /* Handle case of reg or-masked with const. */
>>> + if (GET_CODE (use) == IOR && CONST_INT_P (XEXP (use, 1)) && operand_reg[0])
>>> + {
>>> + used_size =
>>> + HOST_BITS_PER_WIDE_INT - clz_hwi (~UINTVAL (XEXP (use, 1)));
>>> + operand_size[0] = MIN (operand_size[0], used_size);
>>> + }
>>> +
>>> + /* Ignore the use of a in 'a = a + b'. */
>>> + /* TODO: handle GET_CODE ((SET_DEST (set))) == SUBREG. */
>>> + if (set != NULL_RTX && REG_P (SET_DEST (set)))
>>> + for (i = 0; i < nr_operands; ++i)
>>> + operand_ignore[i] = (operand_reg[i]
>>> + && (REGNO (SET_DEST (set)) == operand_regno[i]));
>>> +
>>> + /* Handle the case a reg is combined with don't care bits. */
>>> + if (nr_operands == 2 && operand_reg[0] && operand_reg[1]
>>> + && operand_size[0] != operand_size[1])
>>> + {
>>> + smallest = operand_size[0] > operand_size[1];
>>> +
>>> + if (paradoxical_subreg_p (XEXP (use, smallest)))
>>> + operand_size[1 - smallest] = operand_size[smallest];
>>> + }
>>> +
>>> + /* Register the operand use, if necessary. */
>>> + for (i = 0; i < nr_operands; ++i)
>>> + if (!operand_reg[i])
>>> + note_use (&XEXP (use, i), pattern);
>>> + else if (!operand_ignore[i])
>>> + {
>>> + p = register_use (operand_size[i], operand_regno[i], operand_offset[i],
>>> + &XEXP (use, i));
>>> + register_prop (set, p);
>>> + }
>>> +}
>>> +
>>> +/* Register promoted SUBREG in promoted_subreg. */
>>> +
>>> +static void
>>> +register_promoted_subreg (rtx subreg)
>>> +{
>>> + int index = REGNO (SUBREG_REG (subreg));
>>> +
>>> + if (promoted_subreg[index] == NULL)
>>> + promoted_subreg[index] = VEC_alloc (rtx, heap, 10);
>>> +
>>> + VEC_safe_push (rtx, heap, promoted_subreg[index], subreg);
>>> +}
>>> +
>>> +/* Note promoted subregs in X. */
>>> +
>>> +static int
>>> +note_promoted_subreg (rtx *x, void *y ATTRIBUTE_UNUSED)
>>> +{
>>> + rtx subreg = *x;
>>> +
>>> + if (promoted_subreg_p (subreg) && !fixed_promoted_subreg_p (subreg)
>>> + && REG_P (SUBREG_REG (subreg)))
>>> + register_promoted_subreg (subreg);
>>> +
>>> + return 0;
>>> +}
>>> +
>>> +/* Handle use X in pattern DATA noted by note_uses. */
>>> +
>>> +static void
>>> +note_use (rtx *x, void *data)
>>> +{
>>> + rtx use = *x;
>>> + rtx pattern = (rtx)data;
>>> + int use_size, use_offset;
>>> + unsigned int use_regno;
>>> + rtx set;
>>> + use_type *p;
>>> +
>>> + for_each_rtx (x, note_promoted_subreg, NULL);
>>> +
>>> + set = get_set (use, pattern);
>>> +
>>> + switch (GET_CODE (use))
>>> + {
>>> + case REG:
>>> + case SUBREG:
>>> + if (!reg_use_p (use, &use_size, &use_regno, &use_offset))
>>> + {
>>> + note_embedded_uses (use, pattern);
>>> + return;
>>> + }
>>> + p = register_use (use_size, use_regno, use_offset, x);
>>> + register_prop (set, p);
>>> + return;
>>> + case SIGN_EXTEND:
>>> + case ZERO_EXTEND:
>>> + if (!reg_use_p (XEXP (use, 0), &use_size, &use_regno, &use_offset))
>>> + {
>>> + note_embedded_uses (use, pattern);
>>> + return;
>>> + }
>>> + p = register_use (use_size, use_regno, use_offset, x);
>>> + register_prop (set, p);
>>> + return;
>>> + case IOR:
>>> + case AND:
>>> + case XOR:
>>> + case PLUS:
>>> + case MINUS:
>>> + note_restricted_op_use (set, use, 2, pattern);
>>> + return;
>>> + case NOT:
>>> + case NEG:
>>> + note_restricted_op_use (set, use, 1, pattern);
>>> + return;
>>> + case ASHIFT:
>>> + if (!reg_use_p (XEXP (use, 0), &use_size, &use_regno, &use_offset)
>>> + || !CONST_INT_P (XEXP (use, 1))
>>> + || INTVAL (XEXP (use, 1)) <= 0
>>> + || paradoxical_subreg_p (XEXP (use, 0)))
>>> + {
>>> + note_embedded_uses (use, pattern);
>>> + return;
>>> + }
>>> + (void)register_use (use_size - INTVAL (XEXP (use, 1)), use_regno,
>>> + use_offset, x);
>>> + return;
>>> + default:
>>> + note_embedded_uses (use, pattern);
>>> + return;
>>> + }
>>> +}
>>> +
>>> +/* Check whether reg REGNO is implicitly used. */
>>> +
>>> +static bool
>>> +implicit_use_p (int regno ATTRIBUTE_UNUSED)
>>> +{
>>> +#ifdef EPILOGUE_USES
>>> + if (EPILOGUE_USES (regno))
>>> + return true;
>>> +#endif
>>> +
>>> +#ifdef EH_USES
>>> + if (EH_USES (regno))
>>> + return true;
>>> +#endif
>>> +
>>> + return false;
>>> +}
>>> +
>>> +/* Check whether reg REGNO should be skipped in analysis. */
>>> +
>>> +static bool
>>> +skip_reg_p (int regno)
>>> +{
>>> + /* TODO: handle hard registers. The problem with hard registers is that
>>> + a DI use of r0 can mean a 64bit use of r0 and a 32 bit use of r1.
>>> + We don't handle that properly. */
>>> + return implicit_use_p (regno) || HARD_REGISTER_NUM_P (regno);
>>> +}
>>> +
>>> +/* Note the uses of argument registers in call INSN. */
>>> +
>>> +static void
>>> +note_call_uses (rtx insn)
>>> +{
>>> + rtx link, link_expr;
>>> +
>>> + if (!CALL_P (insn))
>>> + return;
>>> +
>>> + for (link = CALL_INSN_FUNCTION_USAGE (insn); link; link = XEXP (link, 1))
>>> + {
>>> + link_expr = XEXP (link, 0);
>>> +
>>> + if (GET_CODE (link_expr) == USE)
>>> + note_use (&XEXP (link_expr, 0), link);
>>> + }
>>> +}
>>> +
>>> +/* Dump the biggest uses found. */
>>> +
>>> +static void
>>> +dump_biggest_use (void)
>>> +{
>>> + int i;
>>> +
>>> + if (!dump_file)
>>> + return;
>>> +
>>> + fprintf (dump_file, "biggest_use:\n");
>>> +
>>> + for (i = 0; i < n_regs; i++)
>>> + if (biggest_use[i] > 0)
>>> + fprintf (dump_file, "reg %d: size %d\n", i, biggest_use[i]);
>>> +
>>> + fprintf (dump_file, "\n");
>>> +}
>>> +
>>> +/* Calculate the biggest use mode for all regs. */
>>> +
>>> +static void
>>> +calculate_biggest_use (void)
>>> +{
>>> + basic_block bb;
>>> + rtx insn;
>>> +
>>> + /* For all insns, call note_use for each use in insn. */
>>> + FOR_EACH_BB (bb)
>>> + FOR_BB_INSNS (bb, insn)
>>> + {
>>> + if (!NONDEBUG_INSN_P (insn))
>>> + continue;
>>> +
>>> + note_uses (&PATTERN (insn), note_use, PATTERN (insn));
>>> +
>>> + if (CALL_P (insn))
>>> + note_call_uses (insn);
>>> + }
>>> +
>>> + dump_biggest_use ();
>>> +}
>>> +
>>> +/* Register a propagation USE in SET in the props vector. */
>>> +
>>> +static void
>>> +register_prop (rtx set, use_type *use)
>>> +{
>>> + prop_type *p;
>>> + int regno;
>>> +
>>> + if (set == NULL_RTX || use == NULL)
>>> + return;
>>> +
>>> + if (!REG_P (SET_DEST (set)))
>>> + return;
>>> +
>>> + regno = REGNO (SET_DEST (set));
>>> +
>>> + if (skip_reg_p (regno))
>>> + return;
>>> +
>>> + if (props[regno] == NULL)
>>> + props[regno] = VEC_alloc (prop_type, heap, 4);
>>> +
>>> + VEC_safe_push (prop_type, heap, props[regno], NULL);
>>> + p = VEC_last (prop_type, props[regno]);
>>> + p->set = set;
>>> + p->uses_regno = use->regno;
>>> + p->uses_index = VEC_length (use_type, uses[use->regno]) - 1;
>>> +}
>>> +
>>> +/* Add REGNO to the worklist. */
>>> +
>>> +static void
>>> +add_to_wl (int regno)
>>> +{
>>> + if (in_wl[regno])
>>> + return;
>>> +
>>> + if (biggest_use[regno] > 0
>>> + && biggest_use[regno] == GET_MODE_BITSIZE (PSEUDO_REGNO_MODE (regno)))
>>> + return;
>>> +
>>> + if (VEC_empty (prop_type, props[regno]))
>>> + return;
>>> +
>>> + if (propagated_size[regno] != NONE
>>> + && propagated_size[regno] == biggest_use[regno])
>>> + return;
>>> +
>>> + VEC_safe_push (int, heap, wl, regno);
>>> + in_wl[regno] = true;
>>> +}
>>> +
>>> +/* Pop a reg from the worklist and return it. */
>>> +
>>> +static int
>>> +pop_wl (void)
>>> +{
>>> + int regno = VEC_pop (int, wl);
>>> + in_wl[regno] = false;
>>> + return regno;
>>> +}
>>> +
>>> +/* Propagate the use size DEST_SIZE of a reg to use P. */
>>> +
>>> +static int
>>> +propagate_size (int dest_size, use_type *p)
>>> +{
>>> + if (dest_size == 0)
>>> + return 0;
>>> +
>>> + return p->offset + MIN (p->size - p->offset, dest_size);
>>> +}
>>> +
>>> +/* Get the biggest use of REGNO from the uses vector. */
>>> +
>>> +static int
>>> +get_biggest_use (unsigned int regno)
>>> +{
>>> + int ix;
>>> + use_type *p;
>>> + int max = 0;
>>> +
>>> + gcc_assert (uses[regno] != NULL);
>>> +
>>> + FOR_EACH_VEC_ELT (use_type, uses[regno], ix, p)
>>> + max = MAX (max, p->size);
>>> +
>>> + return max;
>>> +}
>>> +
>>> +/* Propagate the use size DEST_SIZE of a reg to the uses in USE. */
>>> +
>>> +static void
>>> +propagate_to_use (int dest_size, use_type *use)
>>> +{
>>> + int new_use_size;
>>> + int prev_biggest_use;
>>> + int *current;
>>> +
>>> + new_use_size = propagate_size (dest_size, use);
>>> +
>>> + if (new_use_size >= use->size)
>>> + return;
>>> +
>>> + use->size = new_use_size;
>>> +
>>> + current = &biggest_use[use->regno];
>>> +
>>> + prev_biggest_use = *current;
>>> + *current = get_biggest_use (use->regno);
>>> +
>>> + if (*current >= prev_biggest_use)
>>> + return;
>>> +
>>> + add_to_wl (use->regno);
>>> +
>>> + if (dump_file)
>>> + fprintf (dump_file, "%d: %d -> %d\n", use->regno, prev_biggest_use,
>>> + *current);
>>> +
>>> +}
>>> +
>>> +/* Propagate the biggest use of a reg REGNO to all its uses, and note
>>> + propagations in NR_PROPAGATIONS. */
>>> +
>>> +static void
>>> +propagate_to_uses (int regno, int *nr_propagations)
>>> +{
>>> + int ix;
>>> + prop_type *p;
>>> +
>>> + gcc_assert (!(propagated_size[regno] == NONE
>>> + && propagated_size[regno] == biggest_use[regno]));
>>> +
>>> + FOR_EACH_VEC_ELT (prop_type, props[regno], ix, p)
>>> + {
>>> + use_type *use = VEC_index (use_type, uses[p->uses_regno], p->uses_index);
>>> + propagate_to_use (biggest_use[regno], use);
>>> + ++(*nr_propagations);
>>> + }
>>> +
>>> + propagated_size[regno] = biggest_use[regno];
>>> +}
>>> +
>>> +/* Improve biggest_use array iteratively. */
>>> +
>>> +static void
>>> +propagate (void)
>>> +{
>>> + int i;
>>> + int nr_propagations = 0;
>>> +
>>> + /* Initialize work list. */
>>> +
>>> + for (i = 0; i < n_regs; ++i)
>>> + add_to_wl (i);
>>> +
>>> + /* Work the work list. */
>>> +
>>> + if (dump_file)
>>> + fprintf (dump_file, "propagations: \n");
>>> + while (!VEC_empty (int, wl))
>>> + propagate_to_uses (pop_wl (), &nr_propagations);
>>> +
>>> + if (dump_file)
>>> + fprintf (dump_file, "\nnr_propagations: %d\n\n", nr_propagations);
>>> +}
>>> +
>>> +/* Check whether this is a sign/zero extension. */
>>> +
>>> +static bool
>>> +extension_p (rtx insn, rtx *dest, rtx *inner, int *preserved_size)
>>> +{
>>> + rtx src, op0;
>>> +
>>> + /* Detect set of reg. */
>>> + if (GET_CODE (PATTERN (insn)) != SET)
>>> + return false;
>>> +
>>> + src = SET_SRC (PATTERN (insn));
>>> + *dest = SET_DEST (PATTERN (insn));
>>> +
>>> + if (!REG_P (*dest))
>>> + return false;
>>> +
>>> + /* Detect sign or zero extension. */
>>> + if (GET_CODE (src) == ZERO_EXTEND || GET_CODE (src) == SIGN_EXTEND
>>> + || (GET_CODE (src) == AND && CONST_INT_P (XEXP (src, 1))))
>>> + {
>>> + op0 = XEXP (src, 0);
>>> +
>>> + /* Determine amount of least significant bits preserved by operation. */
>>> + if (GET_CODE (src) == AND)
>>> + *preserved_size = ctz_hwi (~UINTVAL (XEXP (src, 1)));
>>> + else
>>> + *preserved_size = GET_MODE_BITSIZE (GET_MODE (op0));
>>> +
>>> + if (GET_CODE (op0) == SUBREG)
>>> + {
>>> + if (subreg_lsb (op0) != 0)
>>> + return false;
>>> +
>>> + *inner = SUBREG_REG (op0);
>>> +
>>> + if (GET_MODE_CLASS (GET_MODE (*dest))
>>> + != GET_MODE_CLASS (GET_MODE (*inner)))
>>> + return false;
>>> +
>>> + return true;
>>> + }
>>> + else if (REG_P (op0))
>>> + {
>>> + *inner = op0;
>>> +
>>> + if (GET_MODE_CLASS (GET_MODE (*dest))
>>> + != GET_MODE_CLASS (GET_MODE (*inner)))
>>> + return false;
>>> +
>>> + return true;
>>> + }
>>> + else if (GET_CODE (op0) == TRUNCATE)
>>> + {
>>> + *inner = XEXP (op0, 0);
>>> + return true;
>>> + }
>>> + }
>>> +
>>> + return false;
>>> +}
>>> +
>>> +/* Find extensions and store them in the extensions vector. */
>>> +
>>> +static bool
>>> +find_extensions (void)
>>> +{
>>> + basic_block bb;
>>> + rtx insn, dest, inner;
>>> + int preserved_size;
>>> +
>>> + /* For all insns, call note_use for each use in insn. */
>>> + FOR_EACH_BB (bb)
>>> + FOR_BB_INSNS (bb, insn)
>>> + {
>>> + if (!NONDEBUG_INSN_P (insn))
>>> + continue;
>>> +
>>> + if (!extension_p (insn, &dest, &inner, &preserved_size))
>>> + continue;
>>> +
>>> + VEC_safe_push (rtx, heap, extensions, insn);
>>> +
>>> + if (dump_file)
>>> + fprintf (dump_file,
>>> + "found extension %u with preserved size %d defining"
>>> + " reg %d\n",
>>> + INSN_UID (insn), preserved_size, REGNO (dest));
>>> + }
>>> +
>>> + if (dump_file)
>>> + {
>>> + if (!VEC_empty (rtx, extensions))
>>> + fprintf (dump_file, "\n");
>>> + else
>>> + fprintf (dump_file, "no extensions found.\n");
>>> + }
>>> +
>>> + return !VEC_empty (rtx, extensions);
>>> +}
>>> +
>>> +/* Check whether this is a redundant sign/zero extension. */
>>> +
>>> +static bool
>>> +redundant_extension_p (rtx insn, rtx *dest, rtx *inner, int *preserved_size)
>>> +{
>>> + int biggest_dest_use;
>>> +
>>> + if (!extension_p (insn, dest, inner, preserved_size))
>>> + gcc_unreachable ();
>>> +
>>> + biggest_dest_use = biggest_use[REGNO (*dest)];
>>> +
>>> + if (biggest_dest_use == SKIP_REG)
>>> + return false;
>>> +
>>> + if (*preserved_size < biggest_dest_use)
>>> + return false;
>>> +
>>> + return true;
>>> +}
>>> +
>>> +/* Find the redundant extensions in the extensions vector and move them to the
>>> + redundant_extensions vector. */
>>> +
>>> +static void
>>> +find_redundant_extensions (void)
>>> +{
>>> + rtx insn, dest, inner;
>>> + int ix;
>>> + bool found = false;
>>> + int preserved_size;
>>> +
>>> + FOR_EACH_VEC_ELT_REVERSE (rtx, extensions, ix, insn)
>>> + if (redundant_extension_p (insn, &dest, &inner, &preserved_size))
>>> + {
>>> + VEC_safe_push (rtx, heap, redundant_extensions, insn);
>>> + VEC_unordered_remove (rtx, extensions, ix);
>>> +
>>> + if (dump_file)
>>> + fprintf (dump_file,
>>> + "found redundant extension %u with preserved size %d"
>>> + " defining reg %d\n",
>>> + INSN_UID (insn), preserved_size, REGNO (dest));
>>> + found = true;
>>> + }
>>> +
>>> + if (dump_file && found)
>>> + fprintf (dump_file, "\n");
>>> +}
>>> +
>>> +/* Reset promotion of subregs or REG. */
>>> +
>>> +static void
>>> +reset_promoted_subreg (rtx reg)
>>> +{
>>> + int ix;
>>> + rtx subreg;
>>> +
>>> + if (promoted_subreg[REGNO (reg)] == NULL)
>>> + return;
>>> +
>>> + FOR_EACH_VEC_ELT (rtx, promoted_subreg[REGNO (reg)], ix, subreg)
>>> + {
>>> + SUBREG_PROMOTED_UNSIGNED_SET (subreg, 0);
>>> + SUBREG_PROMOTED_VAR_P (subreg) = 0;
>>> + }
>>> +
>>> + VEC_free (rtx, heap, promoted_subreg[REGNO (reg)]);
>>> +}
>>> +
>>> +/* Try to remove or replace the redundant extension INSN which extends INNER and
>>> + writes to DEST. */
>>> +
>>> +static void
>>> +try_remove_or_replace_extension (rtx insn, rtx dest, rtx inner)
>>> +{
>>> + rtx cp_src, cp_dest, seq = NULL_RTX, one;
>>> +
>>> + /* Check whether replacement is needed. */
>>> + if (dest != inner)
>>> + {
>>> + start_sequence ();
>>> +
>>> + /* Determine the proper replacement operation. */
>>> + if (GET_MODE (dest) == GET_MODE (inner))
>>> + {
>>> + cp_src = inner;
>>> + cp_dest = dest;
>>> + }
>>> + else if (GET_MODE_SIZE (GET_MODE (dest))
>>> + > GET_MODE_SIZE (GET_MODE (inner)))
>>> + {
>>> + emit_clobber (dest);
>>> + cp_src = inner;
>>> + cp_dest = gen_lowpart_SUBREG (GET_MODE (inner), dest);
>>> + }
>>> + else
>>> + {
>>> + cp_src = gen_lowpart_SUBREG (GET_MODE (dest), inner);
>>> + cp_dest = dest;
>>> + }
>>> +
>>> + emit_move_insn (cp_dest, cp_src);
>>> +
>>> + seq = get_insns ();
>>> + end_sequence ();
>>> +
>>> + /* If the replacement is not supported, bail out. */
>>> + for (one = seq; one != NULL_RTX; one = NEXT_INSN (one))
>>> + if (recog_memoized (one) < 0 && GET_CODE (PATTERN (one)) != CLOBBER)
>>> + return;
>>> +
>>> + /* Insert the replacement. */
>>> + emit_insn_before (seq, insn);
>>> + }
>>> +
>>> + /* Note replacement/removal in the dump. */
>>> + if (dump_file)
>>> + {
>>> + fprintf (dump_file, "redundant extension %u ", INSN_UID (insn));
>>> + if (dest != inner)
>>> + fprintf (dump_file, "replaced by %u\n", INSN_UID (seq));
>>> + else
>>> + fprintf (dump_file, "removed\n");
>>> + }
>>> +
>>> + /* Remove the extension. */
>>> + delete_insn (insn);
>>> +
>>> + reset_promoted_subreg (dest);
>>> +}
>>> +
>>> +/* Setup the variables at the start of the pass. */
>>> +
>>> +static void
>>> +init_pass (void)
>>> +{
>>> + int i;
>>> +
>>> + biggest_use = XNEWVEC (int, n_regs);
>>> + promoted_subreg = XCNEWVEC (VEC (rtx,heap) *, n_regs);
>>> + propagated_size = XNEWVEC (int, n_regs);
>>> +
>>> + /* Initialize biggest_use for all regs to 0. If a reg is used implicitly, we
>>> + handle that reg conservatively and set it to SKIP_REG instead. */
>>> + for (i = 0; i < n_regs; i++)
>>> + {
>>> + biggest_use[i] = skip_reg_p (i) ? SKIP_REG : 0;
>>> + propagated_size[i] = NONE;
>>> + }
>>> +
>>> + extensions = VEC_alloc (rtx, heap, 10);
>>> + redundant_extensions = VEC_alloc (rtx, heap, 10);
>>> +
>>> + wl = VEC_alloc (int, heap, 50);
>>> + in_wl = XNEWVEC (bool, n_regs);
>>> +
>>> + uses = XNEWVEC (typeof (*uses), n_regs);
>>> + props = XNEWVEC (typeof (*props), n_regs);
>>> +
>>> + for (i = 0; i < n_regs; ++i)
>>> + {
>>> + uses[i] = NULL;
>>> + props[i] = NULL;
>>> + in_wl[i] = false;
>>> + }
>>> +}
>>> +
>>> +/* Find redundant extensions and remove or replace them if possible. */
>>> +
>>> +static void
>>> +remove_redundant_extensions (void)
>>> +{
>>> + rtx insn, dest, inner;
>>> + int preserved_size;
>>> + int ix;
>>> +
>>> + if (!find_extensions ())
>>> + return;
>>> +
>>> + calculate_biggest_use ();
>>> +
>>> + find_redundant_extensions ();
>>> +
>>> + if (!VEC_empty (rtx, extensions))
>>> + {
>>> + propagate ();
>>> +
>>> + find_redundant_extensions ();
>>> + }
>>> +
>>> + gcc_checking_assert (n_regs == max_reg_num ());
>>> +
>>> + FOR_EACH_VEC_ELT (rtx, redundant_extensions, ix, insn)
>>> + {
>>> + extension_p (insn, &dest, &inner, &preserved_size);
>>> + try_remove_or_replace_extension (insn, dest, inner);
>>> + }
>>> +
>>> + if (dump_file)
>>> + fprintf (dump_file, "\n");
>>> +}
>>> +
>>> +/* Free the variables at the end of the pass. */
>>> +
>>> +static void
>>> +finish_pass (void)
>>> +{
>>> + int i;
>>> +
>>> + XDELETEVEC (propagated_size);
>>> +
>>> + VEC_free (rtx, heap, extensions);
>>> + VEC_free (rtx, heap, redundant_extensions);
>>> +
>>> + VEC_free (int, heap, wl);
>>> +
>>> + for (i = 0; i < n_regs; ++i)
>>> + {
>>> + if (uses[i] != NULL)
>>> + VEC_free (use_type, heap, uses[i]);
>>> +
>>> + if (props[i] != NULL)
>>> + VEC_free (prop_type, heap, props[i]);
>>> + }
>>> +
>>> + XDELETEVEC (uses);
>>> + XDELETEVEC (props);
>>> + XDELETEVEC (biggest_use);
>>> +
>>> + for (i = 0; i < n_regs; ++i)
>>> + if (promoted_subreg[i] != NULL)
>>> + VEC_free (rtx, heap, promoted_subreg[i]);
>>> + XDELETEVEC (promoted_subreg);
>>> +}
>>> +
>>> +/* Remove redundant extensions. */
>>> +
>>> +static unsigned int
>>> +rest_of_handle_ee (void)
>>> +{
>>> + n_regs = max_reg_num ();
>>> +
>>> + init_pass ();
>>> + remove_redundant_extensions ();
>>> + finish_pass ();
>>> + return 0;
>>> +}
>>> +
>>> +/* Run ee pass when flag_ee is set at optimization level > 0. */
>>> +
>>> +static bool
>>> +gate_handle_ee (void)
>>> +{
>>> + return (optimize > 0 && flag_ee);
>>> +}
>>> +
>>> +struct rtl_opt_pass pass_ee =
>>> +{
>>> + {
>>> + RTL_PASS,
>>> + "ee", /* name */
>>> + gate_handle_ee, /* gate */
>>> + rest_of_handle_ee, /* execute */
>>> + NULL, /* sub */
>>> + NULL, /* next */
>>> + 0, /* static_pass_number */
>>> + TV_EE, /* tv_id */
>>> + 0, /* properties_required */
>>> + 0, /* properties_provided */
>>> + 0, /* properties_destroyed */
>>> + 0, /* todo_flags_start */
>>> + TODO_ggc_collect |
>>> + TODO_verify_rtl_sharing, /* todo_flags_finish */
>>> + }
>>> +};
>>> Index: gcc/common.opt
>>> ===================================================================
>>> --- gcc/common.opt (revision 189409)
>>> +++ gcc/common.opt (working copy)
>>> @@ -1067,6 +1067,10 @@ feliminate-dwarf2-dups
>>> Common Report Var(flag_eliminate_dwarf2_dups)
>>> Perform DWARF2 duplicate elimination
>>>
>>> +fextension-elimination
>>> +Common Report Var(flag_ee) Init(0) Optimization
>>> +Perform extension elimination
>>> +
>>> fipa-sra
>>> Common Report Var(flag_ipa_sra) Init(0) Optimization
>>> Perform interprocedural reduction of aggregates
>>> Index: gcc/Makefile.in
>>> ===================================================================
>>> --- gcc/Makefile.in (revision 189409)
>>> +++ gcc/Makefile.in (working copy)
>>> @@ -1218,6 +1218,7 @@ OBJS = \
>>> dwarf2asm.o \
>>> dwarf2cfi.o \
>>> dwarf2out.o \
>>> + ee.o \
>>> ebitmap.o \
>>> emit-rtl.o \
>>> et-forest.o \
>>> @@ -2971,6 +2972,12 @@ cprop.o : cprop.c $(CONFIG_H) $(SYSTEM_H
>>> $(TM_P_H) $(PARAMS_H) cselib.h $(EXCEPT_H) $(TREE_H) $(TIMEVAR_H) \
>>> intl.h $(OBSTACK_H) $(TREE_PASS_H) $(DF_H) $(DBGCNT_H) $(TARGET_H) \
>>> $(DF_H) $(CFGLOOP_H)
>>> +ee.o : ee.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(RTL_H) \
>>> + hard-reg-set.h $(FLAGS_H) $(BASIC_BLOCK_H) $(FUNCTION_H) output.h \
>>> + $(DF_H) $(TIMEVAR_H) tree-pass.h $(RECOG_H) $(EXPR_H) \
>>> + $(REGS_H) $(TREE_H) $(TM_P_H) insn-config.h $(INSN_ATTR_H) $(TOPLEV_H) \
>>> + $(DIAGNOSTIC_CORE_H) $(TARGET_H) $(OPTABS_H) insn-codes.h rtlhooks-def.h \
>>> + $(PARAMS_H) $(CGRAPH_H)
>>> gcse.o : gcse.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(RTL_H) \
>>> $(REGS_H) hard-reg-set.h $(FLAGS_H) insn-config.h $(GGC_H) \
>>> $(RECOG_H) $(EXPR_H) $(BASIC_BLOCK_H) $(FUNCTION_H) toplev.h $(DIAGNOSTIC_CORE_H) \
>>> Index: gcc/passes.c
>>> ===================================================================
>>> --- gcc/passes.c (revision 189409)
>>> +++ gcc/passes.c (working copy)
>>> @@ -1552,6 +1552,7 @@ init_optimization_passes (void)
>>> NEXT_PASS (pass_initialize_regs);
>>> NEXT_PASS (pass_ud_rtl_dce);
>>> NEXT_PASS (pass_combine);
>>> + NEXT_PASS (pass_ee);
>>> NEXT_PASS (pass_if_after_combine);
>>> NEXT_PASS (pass_partition_blocks);
>>> NEXT_PASS (pass_regmove);
>>
>>
>
>
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