Re: [PATCH] Add a new option "-fmerge-bitfields" (patch / doc inside)

2016-02-17 Thread Richard Biener 
On Wed, 17 Feb 2016, Richard Biener wrote:

> On Wed, 17 Feb 2016, Bernd Schmidt wrote:
> 
> > 
> > 
> > On 02/17/2016 02:18 PM, Daniel Gutson wrote:
> > > On Wed, Nov 26, 2014 at 5:46 AM, Andrew Pinski  wrote:
> > 
> > > > FYI. This causes gfc_add_interface_mapping in fortrant/trans-expr.c to
> > > > be miscompiled for aarch64-linux-gnu.  I am still debugging it and
> > > > trying to get a smaller testcase.
> > > 
> > > Hello,
> > > 
> > > is there any update on this?
> > 
> > Is this a PR somewhere?
> 
> I think there are several.  But rather than a special pass I hope
> we can get to lowering all bitfield accesses somewhere and make
> our regular passes deal with the combining.  I've had multiple
> approaches at this but never went through finalizing them
> (tried doing that too early all the times I guess).

Whee.  2011 - https://gcc.gnu.org/ml/gcc-patches/2011-06/msg01233.html.
I remember updating this for DECL_BIT_FIELD_REPRESENTATIVE we have now,
simplifying this.  I also remember doing the lowering (using
DECL_BIT_FIELD_REPRESENTATIVE) at gimplification time.  And then
bitfield lowering was part of the original mem-ref branch (that didn't
get merged).

Richard.

Re: [PATCH] Add a new option "-fmerge-bitfields" (patch / doc inside)

2016-02-17 Thread Richard Biener 
On Wed, 17 Feb 2016, Bernd Schmidt wrote:

> 
> 
> On 02/17/2016 02:18 PM, Daniel Gutson wrote:
> > On Wed, Nov 26, 2014 at 5:46 AM, Andrew Pinski  wrote:
> 
> > > FYI. This causes gfc_add_interface_mapping in fortrant/trans-expr.c to
> > > be miscompiled for aarch64-linux-gnu.  I am still debugging it and
> > > trying to get a smaller testcase.
> > 
> > Hello,
> > 
> > is there any update on this?
> 
> Is this a PR somewhere?

I think there are several.  But rather than a special pass I hope
we can get to lowering all bitfield accesses somewhere and make
our regular passes deal with the combining.  I've had multiple
approaches at this but never went through finalizing them
(tried doing that too early all the times I guess).

Richard.

Re: [PATCH] Add a new option "-fmerge-bitfields" (patch / doc inside)

2016-02-17 Thread Jakub Jelinek 
On Wed, Feb 17, 2016 at 02:45:16PM +0100, Bernd Schmidt wrote:
> 
> 
> On 02/17/2016 02:18 PM, Daniel Gutson wrote:
> >On Wed, Nov 26, 2014 at 5:46 AM, Andrew Pinski  wrote:
> 
> >>FYI. This causes gfc_add_interface_mapping in fortrant/trans-expr.c to
> >>be miscompiled for aarch64-linux-gnu.  I am still debugging it and
> >>trying to get a smaller testcase.
> >
> >Hello,
> >
> >is there any update on this?
> 
> Is this a PR somewhere?

Perhaps related to PR22141?

Jakub

Re: [PATCH] Add a new option "-fmerge-bitfields" (patch / doc inside)

2016-02-17 Thread Bernd Schmidt 



On 02/17/2016 02:18 PM, Daniel Gutson wrote:

On Wed, Nov 26, 2014 at 5:46 AM, Andrew Pinski  wrote:



FYI. This causes gfc_add_interface_mapping in fortrant/trans-expr.c to
be miscompiled for aarch64-linux-gnu.  I am still debugging it and
trying to get a smaller testcase.


Hello,

is there any update on this?


Is this a PR somewhere?


Bernd

Re: [PATCH] Add a new option "-fmerge-bitfields" (patch / doc inside)

2016-02-17 Thread Daniel Gutson 
&& bf_access_candidate_p (gimple_assign_rhs1
>> + (cc->head_copy->load_stmt),
>> + _off))
>> + off = mrg_off;
>> +   if (cc && cc->merged)
>> + {
>> +   tree head_rhs = gimple_assign_rhs1 
>> (cc->head_copy->load_stmt);
>> +   switch (TREE_CODE (head_rhs))
>> + {
>> + case COMPONENT_REF:
>> +   if (bf_access_candidate_p (head_rhs, _off))
>> + off = mrg_off;
>> +   break;
>> + case BIT_FIELD_REF:
>> +   off = tree_to_uhwi (TREE_OPERAND (head_rhs, 2));
>> +   break;
>> + default:
>> +   break;
>> + }
>> + }
>> +
>> +   if (cc && (cc->modified))
>> + {
>> +   tree tmp_ssa;
>> +   tree itype = make_node (INTEGER_TYPE);
>> +   TYPE_PRECISION (itype) = TREE_INT_CST_LOW (size);
>> +   fixup_unsigned_type (itype);
>> +   lower_bitfield_read (, off, size, itype);
>> +   tmp_ssa =
>> + make_ssa_name (create_tmp_var (itype, NULL), 
>> cc->load_stmt);
>> +   gimple_assign_set_lhs (cc->load_stmt, tmp_ssa);
>> +   update_stmt (cc->load_stmt);
>> +   gimple_assign_set_rhs1 (cc->store_stmt, tmp_ssa);
>> +   update_stmt (cc->store_stmt);
>> + }
>> +   else if (cc && cc->merged)
>> + {
>> +   gsi_remove (, true);
>> +   deleted = true;
>> + }
>> + }
>> +   /* Lower a bit-field write.  */
>> +   ref = gimple_assign_lhs (stmt);
>> +   if (bf_access_candidate_p (ref, ))
>> + {
>> +   bfcopy *cc = NULL;
>> +   bitfield_stmt_bfcopy_pair st_cpy (stmt, NULL);
>> +   bitfield_stmt_bfcopy_pair *p_st_cpy;
>> +   unsigned HOST_WIDE_INT mrg_off;
>> +       p_st_cpy = bf_stmnt_cpy->find (_cpy);
>> +   if (p_st_cpy)
>> + cc = p_st_cpy->copy;
>> +
>> +   if (cc && (cc->merged || cc->modified))
>> + size =
>> +   build_int_cst (unsigned_type_node,
>> +  get_merged_bit_field_size (cc->head_copy ?
>> + cc->head_copy :
>> + cc));
>> +   else
>> + size = DECL_SIZE (TREE_OPERAND (ref, 1));
>> +   if (cc && cc->merged
>> +   &&
>> +   bf_access_candidate_p (gimple_assign_lhs
>> +  (cc->head_copy->store_stmt), 
>> _off))
>> + off = mrg_off;
>> +
>> +   if (cc && (cc->modified) && !(cc && cc->merged))
>> + lower_bitfield_write (, off, size);
>> +   else if (cc && cc->merged)
>> + {
>> +   if (gimple_vdef (stmt))
>

Re: [PATCH] Add a new option -fmerge-bitfields (patch / doc inside)

2014-11-26 Thread Andrew Pinski 
);
 +   }
 + }
 +
 +   gsi_remove (gsi, true);
 +   deleted = true;
 + }
 + }
 +   if (gimple_vdef (stmt)  !deleted)
 + reaching_vuse = gimple_vdef (stmt);
 +   if (!deleted)
 + gsi_next (gsi);
 +  }
 +  }
 +  delete bf_stmnt_cpy;
 +}
 +
  /* Perform early intraprocedural SRA.  */
  static unsigned int
  early_intra_sra (void)
  {
sra_mode = SRA_MODE_EARLY_INTRA;
 -  return perform_intra_sra ();
 +  unsigned int res = perform_intra_sra ();
 +  if (flag_tree_bitfield_merge)
 +lower_bitfields ();
 +  return res;
  }

  /* Perform late intraprocedural SRA.  */
 diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c
 index 44656ea..cdb3850 100644
 --- a/gcc/tree-ssa-sccvn.c
 +++ b/gcc/tree-ssa-sccvn.c
 @@ -4410,29 +4410,6 @@ get_next_value_id (void)
return next_value_id++;
  }

 -
 -/* Compare two expressions E1 and E2 and return true if they are equal.  */
 -
 -bool
 -expressions_equal_p (tree e1, tree e2)
 -{
 -  /* The obvious case.  */
 -  if (e1 == e2)
 -return true;
 -
 -  /* If only one of them is null, they cannot be equal.  */
 -  if (!e1 || !e2)
 -return false;
 -
 -  /* Now perform the actual comparison.  */
 -  if (TREE_CODE (e1) == TREE_CODE (e2)
 -   operand_equal_p (e1, e2, OEP_PURE_SAME))
 -return true;
 -
 -  return false;
 -}
 -
 -
  /* Return true if the nary operation NARY may trap.  This is a copy
 of stmt_could_throw_1_p adjusted to the SCCVN IL.  */

 diff --git a/gcc/tree-ssa-sccvn.h b/gcc/tree-ssa-sccvn.h
 index ad99604..d5963b6 100644
 --- a/gcc/tree-ssa-sccvn.h
 +++ b/gcc/tree-ssa-sccvn.h
 @@ -21,10 +21,6 @@
  #ifndef TREE_SSA_SCCVN_H
  #define TREE_SSA_SCCVN_H

 -/* In tree-ssa-sccvn.c  */
 -bool expressions_equal_p (tree, tree);
 -
 -
  /* TOP of the VN lattice.  */
  extern tree VN_TOP;

 diff --git a/gcc/tree.c b/gcc/tree.c
 index 365e89c..8df9812 100644
 --- a/gcc/tree.c
 +++ b/gcc/tree.c
 @@ -12286,4 +12286,44 @@ get_base_address (tree t)
return t;
  }

 +/* Compare two expressions E1 and E2 and return true if they are equal.  */
 +
 +bool
 +expressions_equal_p (const_tree e1, const_tree e2)
 +{
 +  /* The obvious case.  */
 +  if (e1 == e2)
 +return true;
 +
 +  /* If only one of them is null, they cannot be equal.  */
 +  if (!e1 || !e2)
 +return false;
 +
 +  /* Now perform the actual comparison.  */
 +  if (TREE_CODE (e1) == TREE_CODE (e2)
 +   operand_equal_p (e1, e2, OEP_PURE_SAME))
 +return true;
 +
 +  return false;
 +}
 +
 +/* Given a pointer to a tree node, assumed to be some kind of a ..._TYPE
 +   node, return the size in bits for the type if it is a constant, or else
 +   return the alignment for the type if the type's size is not constant, or
 +   else return BITS_PER_WORD if the type actually turns out to be an
 +   ERROR_MARK node.  */
 +
 +unsigned HOST_WIDE_INT
 +simple_type_size_in_bits (const_tree type)
 +{
 +  if (TREE_CODE (type) == ERROR_MARK)
 +return BITS_PER_WORD;
 +  else if (TYPE_SIZE (type) == NULL_TREE)
 +return 0;
 +  else if (tree_fits_uhwi_p (TYPE_SIZE (type)))
 +return tree_to_uhwi (TYPE_SIZE (type));
 +  else
 +return TYPE_ALIGN (type);
 +}
 +
  #include gt-tree.h
 diff --git a/gcc/tree.h b/gcc/tree.h
 index 45f127f..b903089 100644
 --- a/gcc/tree.h
 +++ b/gcc/tree.h
 @@ -4068,6 +4068,7 @@ extern tree substitute_placeholder_in_expr (tree, tree);
((EXP) == 0 || TREE_CONSTANT (EXP) ? (EXP)   \
 : substitute_placeholder_in_expr (EXP, OBJ))

 +extern unsigned HOST_WIDE_INT simple_type_size_in_bits (const_tree type);

  /* stabilize_reference (EXP) returns a reference equivalent to EXP
 but it can be used multiple times
 @@ -4184,6 +4185,11 @@ inlined_function_outer_scope_p (const_tree block)
 (TREE = function_args_iter_cond ((ITER))) != NULL_TREE;  
   \
 function_args_iter_next ((ITER)))

 +
 +/* In dwarf2out.c.  */
 +HOST_WIDE_INT
 +field_byte_offset (const_tree decl);
 +
  /* In tree.c */
  extern unsigned crc32_string (unsigned, const char *);
  extern unsigned crc32_byte (unsigned, char);
 @@ -4340,6 +4346,7 @@ extern tree obj_type_ref_class (tree ref);
  extern bool types_same_for_odr (const_tree type1, const_tree type2);
  extern bool contains_bitfld_component_ref_p (const_tree);
  extern bool type_in_anonymous_namespace_p (const_tree);
 +extern bool expressions_equal_p (const_tree e1, const_tree e2);
  extern bool block_may_fallthru (const_tree);
  extern void using_eh_for_cleanups (void);
  extern bool using_eh_for_cleanups_p (void);


 Regards,
 Zoran



 From: Andrew Pinski [pins...@gmail.com]
 Sent: Thursday, October 16, 2014 4:09 AM
 To: Zoran Jovanovic
 Cc: gcc-patches@gcc.gnu.org; Richard Biener; Bernhard Reutner-Fischer
 Subject: Re: [PATCH] Add a new option -fmerge-bitfields (patch / doc 
 inside)

 On Tue, Apr 22, 2014 at 3:28 AM, Zoran Jovanovic
 zoran.jovano...@imgtec.com wrote:
  Hello,
  Updated doc/invoke.texi by stating that new option is enabled by default 
  at -O2 and higher

RE: [PATCH] Add a new option -fmerge-bitfields (patch / doc inside)

2014-10-29 Thread Zoran Jovanovic 
;
-
-  return false;
-}
-
-
 /* Return true if the nary operation NARY may trap.  This is a copy
of stmt_could_throw_1_p adjusted to the SCCVN IL.  */
 
diff --git a/gcc/tree-ssa-sccvn.h b/gcc/tree-ssa-sccvn.h
index ad99604..d5963b6 100644
--- a/gcc/tree-ssa-sccvn.h
+++ b/gcc/tree-ssa-sccvn.h
@@ -21,10 +21,6 @@
 #ifndef TREE_SSA_SCCVN_H
 #define TREE_SSA_SCCVN_H
 
-/* In tree-ssa-sccvn.c  */
-bool expressions_equal_p (tree, tree);
-
-
 /* TOP of the VN lattice.  */
 extern tree VN_TOP;
 
diff --git a/gcc/tree.c b/gcc/tree.c
index 365e89c..8df9812 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -12286,4 +12286,44 @@ get_base_address (tree t)
   return t;
 }
 
+/* Compare two expressions E1 and E2 and return true if they are equal.  */
+
+bool
+expressions_equal_p (const_tree e1, const_tree e2)
+{
+  /* The obvious case.  */
+  if (e1 == e2)
+return true;
+
+  /* If only one of them is null, they cannot be equal.  */
+  if (!e1 || !e2)
+return false;
+
+  /* Now perform the actual comparison.  */
+  if (TREE_CODE (e1) == TREE_CODE (e2)
+   operand_equal_p (e1, e2, OEP_PURE_SAME))
+return true;
+
+  return false;
+}
+
+/* Given a pointer to a tree node, assumed to be some kind of a ..._TYPE
+   node, return the size in bits for the type if it is a constant, or else
+   return the alignment for the type if the type's size is not constant, or
+   else return BITS_PER_WORD if the type actually turns out to be an
+   ERROR_MARK node.  */
+
+unsigned HOST_WIDE_INT
+simple_type_size_in_bits (const_tree type)
+{
+  if (TREE_CODE (type) == ERROR_MARK)
+return BITS_PER_WORD;
+  else if (TYPE_SIZE (type) == NULL_TREE)
+return 0;
+  else if (tree_fits_uhwi_p (TYPE_SIZE (type)))
+return tree_to_uhwi (TYPE_SIZE (type));
+  else
+return TYPE_ALIGN (type);
+}
+
 #include gt-tree.h
diff --git a/gcc/tree.h b/gcc/tree.h
index 45f127f..b903089 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -4068,6 +4068,7 @@ extern tree substitute_placeholder_in_expr (tree, tree);
   ((EXP) == 0 || TREE_CONSTANT (EXP) ? (EXP)   \
: substitute_placeholder_in_expr (EXP, OBJ))
 
+extern unsigned HOST_WIDE_INT simple_type_size_in_bits (const_tree type);
 
 /* stabilize_reference (EXP) returns a reference equivalent to EXP
but it can be used multiple times
@@ -4184,6 +4185,11 @@ inlined_function_outer_scope_p (const_tree block)
(TREE = function_args_iter_cond ((ITER))) != NULL_TREE;
\
function_args_iter_next ((ITER)))
 
+
+/* In dwarf2out.c.  */
+HOST_WIDE_INT
+field_byte_offset (const_tree decl);
+
 /* In tree.c */
 extern unsigned crc32_string (unsigned, const char *);
 extern unsigned crc32_byte (unsigned, char);
@@ -4340,6 +4346,7 @@ extern tree obj_type_ref_class (tree ref);
 extern bool types_same_for_odr (const_tree type1, const_tree type2);
 extern bool contains_bitfld_component_ref_p (const_tree);
 extern bool type_in_anonymous_namespace_p (const_tree);
+extern bool expressions_equal_p (const_tree e1, const_tree e2);
 extern bool block_may_fallthru (const_tree);
 extern void using_eh_for_cleanups (void);
 extern bool using_eh_for_cleanups_p (void);


Regards,
Zoran



 From: Andrew Pinski [pins...@gmail.com]
 Sent: Thursday, October 16, 2014 4:09 AM
 To: Zoran Jovanovic
 Cc: gcc-patches@gcc.gnu.org; Richard Biener; Bernhard Reutner-Fischer
 Subject: Re: [PATCH] Add a new option -fmerge-bitfields (patch / doc inside)
 
 On Tue, Apr 22, 2014 at 3:28 AM, Zoran Jovanovic
 zoran.jovano...@imgtec.com wrote:
  Hello,
  Updated doc/invoke.texi by stating that new option is enabled by default at 
  -O2 and higher.
  Also, -fmerge-bitfields added to the list  of optimization flags enabled by 
  default  at -O2 and higher.
 
 
 With this patch applied gcc from SPEC 2006 ICEs on aarch64-linux-gnu.
 Here is a reduced testcase:
 typedef struct rtx_def *rtx;
 struct rtx_def
 {
   unsigned int unchanging : 1;
   unsigned int volatil : 1;
   unsigned int in_struct : 1;
   unsigned integrated : 1;
   unsigned frame_related : 1;
 };
 ix86_set_move_mem_attrs_1 (rtx x, rtx dstref)
 {
 ((x)-volatil) = ((dstref)-volatil);
  ((x)-in_struct) = ((dstref)-in_struct);
  ((x)-frame_related) = ((dstref)-frame_related);
  ((x)-unchanging) = ((dstref)-unchanging);
 }
 --- CUT ---
 
 Thanks,
 Andrew Pinski

Re: [PATCH] Add a new option -fmerge-bitfields (patch / doc inside)

2014-10-15 Thread Andrew Pinski 
On Tue, Apr 22, 2014 at 3:28 AM, Zoran Jovanovic
zoran.jovano...@imgtec.com wrote:
 Hello,
 Updated doc/invoke.texi by stating that new option is enabled by default at 
 -O2 and higher.
 Also, -fmerge-bitfields added to the list  of optimization flags enabled by 
 default  at -O2 and higher.


With this patch applied gcc from SPEC 2006 ICEs on aarch64-linux-gnu.
Here is a reduced testcase:
typedef struct rtx_def *rtx;
struct rtx_def
{
  unsigned int unchanging : 1;
  unsigned int volatil : 1;
  unsigned int in_struct : 1;
  unsigned integrated : 1;
  unsigned frame_related : 1;
};
ix86_set_move_mem_attrs_1 (rtx x, rtx dstref)
{
((x)-volatil) = ((dstref)-volatil);
 ((x)-in_struct) = ((dstref)-in_struct);
 ((x)-frame_related) = ((dstref)-frame_related);
 ((x)-unchanging) = ((dstref)-unchanging);
}
--- CUT ---

Thanks,
Andrew Pinski



 Regards,
 Zoran Jovanovic

 --

 Lowering is applied only for bit-fields copy sequences that are merged.
 Data structure representing bit-field copy sequences is renamed and reduced 
 in size.
 Optimization turned on by default for -O2 and higher.
 Some comments fixed.

 Benchmarking performed on WebKit for Android.
 Code size reduction noticed on several files, best examples are:

 core/rendering/style/StyleMultiColData (632-520 bytes)
 core/platform/graphics/FontDescription (1715-1475 bytes)
 core/rendering/style/FillLayer (5069-4513 bytes)
 core/rendering/style/StyleRareInheritedData (5618-5346)
 core/css/CSSSelectorList(4047-3887)
 core/platform/animation/CSSAnimationData (3844-3440 bytes)
 core/css/resolver/FontBuilder (13818-13350 bytes)
 core/platform/graphics/Font (16447-15975 bytes)


 Example:

 One of the motivating examples for this work was copy constructor of the 
 class which contains bit-fields.

 C++ code:
 class A
 {
 public:
 A(const A x);
 unsigned a : 1;
 unsigned b : 2;
 unsigned c : 4;
 };

 A::A(const Ax)
 {
 a = x.a;
 b = x.b;
 c = x.c;
 }

 GIMPLE code without optimization:

   bb 2:
   _3 = x_2(D)-a;
   this_4(D)-a = _3;
   _6 = x_2(D)-b;
   this_4(D)-b = _6;
   _8 = x_2(D)-c;
   this_4(D)-c = _8;
   return;

 Optimized GIMPLE code:
   bb 2:
   _10 = x_2(D)-D.1867;
   _11 = BIT_FIELD_REF _10, 7, 0;
   _12 = this_4(D)-D.1867;
   _13 = _12  128;
   _14 = (unsigned char) _11;
   _15 = _13 | _14;
   this_4(D)-D.1867 = _15;
   return;

 Generated MIPS32r2 assembly code without optimization:
  lw  $3,0($5)
 lbu $2,0($4)
 andi$3,$3,0x1
 andi$2,$2,0xfe
 or  $2,$2,$3
 sb  $2,0($4)
 lw  $3,0($5)
 andi$2,$2,0xf9
 andi$3,$3,0x6
 or  $2,$2,$3
 sb  $2,0($4)
 lw  $3,0($5)
 andi$2,$2,0x87
 andi$3,$3,0x78
 or  $2,$2,$3
 j   $31
 sb  $2,0($4)

 Optimized MIPS32r2 assembly code:
 lw  $3,0($5)
 lbu $2,0($4)
 andi$3,$3,0x7f
 andi$2,$2,0x80
 or  $2,$3,$2
 j   $31
 sb  $2,0($4)


 Algorithm works on basic block level and consists of following 3 major steps:
 1. Go through basic block statements list. If there are statement pairs that 
 implement copy of bit field content from one memory location to another 
 record statements pointers and other necessary data in corresponding data 
 structure.
 2. Identify records that represent adjacent bit field accesses and mark them 
 as merged.
 3. Lower bit-field accesses by using new field size for those that can be 
 merged.


 New command line option -fmerge-bitfields is introduced.


 Tested - passed gcc regression tests for MIPS32r2.


 Changelog -

 gcc/ChangeLog:
 2014-04-22 Zoran Jovanovic (zoran.jovano...@imgtec.com)
   * common.opt (fmerge-bitfields): New option.
   * doc/invoke.texi: Add reference to -fmerge-bitfields.
   * doc/invoke.texi: Add -fmerge-bitfields to the list of optimization
 flags turned on at -O2.
   * tree-sra.c (lower_bitfields): New function.
   Entry for (-fmerge-bitfields).
   (part_of_union_p): New function.
   (bf_access_candidate_p): New function.
   (lower_bitfield_read): New function.
   (lower_bitfield_write): New function.
   (bitfield_stmt_bfcopy_pair::hash): New function.
   (bitfield_stmt_bfcopy_pair::equal): New function.
   (bitfield_stmt_bfcopy_pair::remove): New function.
   (create_and_insert_bfcopy): New function.
   (get_bit_offset): New function.
   (add_stmt_bfcopy_pair): New function.
   (cmp_bfcopies): New function.
   (get_merged_bit_field_size): New function.
   * dwarf2out.c (simple_type_size_in_bits): Move to tree.c.
   (field_byte_offset): Move declaration to tree.h and make it extern.
   * testsuite/gcc.dg/tree-ssa/bitfldmrg1.c: New test.
   * testsuite/gcc.dg/tree-ssa/bitfldmrg2.c: New test.
   *

RE: [PATCH] Add a new option -fmerge-bitfields (patch / doc inside)

2014-04-22 Thread Zoran Jovanovic 
Hello,
Updated doc/invoke.texi by stating that new option is enabled by default at -O2 
and higher. 
Also, -fmerge-bitfields added to the list  of optimization flags enabled by 
default  at -O2 and higher.

Regards,
Zoran Jovanovic

--

Lowering is applied only for bit-fields copy sequences that are merged.
Data structure representing bit-field copy sequences is renamed and reduced in 
size.
Optimization turned on by default for -O2 and higher.
Some comments fixed.

Benchmarking performed on WebKit for Android.
Code size reduction noticed on several files, best examples are:

core/rendering/style/StyleMultiColData (632-520 bytes)
core/platform/graphics/FontDescription (1715-1475 bytes)
core/rendering/style/FillLayer (5069-4513 bytes)
core/rendering/style/StyleRareInheritedData (5618-5346)
core/css/CSSSelectorList(4047-3887)
core/platform/animation/CSSAnimationData (3844-3440 bytes)
core/css/resolver/FontBuilder (13818-13350 bytes)
core/platform/graphics/Font (16447-15975 bytes)


Example:

One of the motivating examples for this work was copy constructor of the class 
which contains bit-fields.

C++ code:
class A
{
public:
A(const A x);
unsigned a : 1;
unsigned b : 2;
unsigned c : 4;
};

A::A(const Ax)
{
a = x.a;
b = x.b;
c = x.c;
}

GIMPLE code without optimization:

  bb 2:
  _3 = x_2(D)-a;
  this_4(D)-a = _3;
  _6 = x_2(D)-b;
  this_4(D)-b = _6;
  _8 = x_2(D)-c;
  this_4(D)-c = _8;
  return;

Optimized GIMPLE code:
  bb 2:
  _10 = x_2(D)-D.1867;
  _11 = BIT_FIELD_REF _10, 7, 0;
  _12 = this_4(D)-D.1867;
  _13 = _12  128;
  _14 = (unsigned char) _11;
  _15 = _13 | _14;
  this_4(D)-D.1867 = _15;
  return;

Generated MIPS32r2 assembly code without optimization:
 lw  $3,0($5)
lbu $2,0($4)
andi$3,$3,0x1
andi$2,$2,0xfe
or  $2,$2,$3
sb  $2,0($4)
lw  $3,0($5)
andi$2,$2,0xf9
andi$3,$3,0x6
or  $2,$2,$3
sb  $2,0($4)
lw  $3,0($5)
andi$2,$2,0x87
andi$3,$3,0x78
or  $2,$2,$3
j   $31
sb  $2,0($4)

Optimized MIPS32r2 assembly code:
lw  $3,0($5)
lbu $2,0($4)
andi$3,$3,0x7f
andi$2,$2,0x80
or  $2,$3,$2
j   $31
sb  $2,0($4)


Algorithm works on basic block level and consists of following 3 major steps:
1. Go through basic block statements list. If there are statement pairs that 
implement copy of bit field content from one memory location to another record 
statements pointers and other necessary data in corresponding data structure.
2. Identify records that represent adjacent bit field accesses and mark them as 
merged.
3. Lower bit-field accesses by using new field size for those that can be 
merged.


New command line option -fmerge-bitfields is introduced.


Tested - passed gcc regression tests for MIPS32r2.


Changelog -

gcc/ChangeLog:
2014-04-22 Zoran Jovanovic (zoran.jovano...@imgtec.com)
  * common.opt (fmerge-bitfields): New option.
  * doc/invoke.texi: Add reference to -fmerge-bitfields.
  * doc/invoke.texi: Add -fmerge-bitfields to the list of optimization
flags turned on at -O2.
  * tree-sra.c (lower_bitfields): New function.
  Entry for (-fmerge-bitfields).
  (part_of_union_p): New function.
  (bf_access_candidate_p): New function.
  (lower_bitfield_read): New function.
  (lower_bitfield_write): New function.
  (bitfield_stmt_bfcopy_pair::hash): New function.
  (bitfield_stmt_bfcopy_pair::equal): New function.
  (bitfield_stmt_bfcopy_pair::remove): New function.
  (create_and_insert_bfcopy): New function.
  (get_bit_offset): New function.
  (add_stmt_bfcopy_pair): New function.
  (cmp_bfcopies): New function.
  (get_merged_bit_field_size): New function.
  * dwarf2out.c (simple_type_size_in_bits): Move to tree.c.
  (field_byte_offset): Move declaration to tree.h and make it extern.
  * testsuite/gcc.dg/tree-ssa/bitfldmrg1.c: New test.
  * testsuite/gcc.dg/tree-ssa/bitfldmrg2.c: New test.
  * tree-ssa-sccvn.c (expressions_equal_p): Move to tree.c.
  * tree-ssa-sccvn.h (expressions_equal_p): Move declaration to tree.h.
  * tree.c (expressions_equal_p): Move from tree-ssa-sccvn.c.
  (simple_type_size_in_bits): Move from dwarf2out.c.
  * tree.h (expressions_equal_p): Add declaration.
  (field_byte_offset): Add declaration.

Patch -

diff --git a/gcc/common.opt b/gcc/common.opt
index da275e5..52c7f58 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -2203,6 +2203,10 @@ ftree-sra
 Common Report Var(flag_tree_sra) Optimization
 Perform scalar replacement of aggregates
 
+fmerge-bitfields
+Common Report Var(flag_tree_bitfield_merge) Optimization
+Merge loads and stores of consecutive bitfields
+
 ftree-ter
 Common Report Var(flag_tree_ter) Optimization

Re: [PATCH] Add a new option -fmerge-bitfields (patch / doc inside)

2014-04-19 Thread Ryan Hill 
On Thu, 17 Apr 2014 11:59:16 +
Zoran Jovanovic zoran.jovano...@imgtec.com wrote:

 --- a/gcc/doc/invoke.texi
 +++ b/gcc/doc/invoke.texi
 @@ -7789,6 +7789,11 @@ pointer alignment information.
  This pass only operates on local scalar variables and is enabled by default
  at @option{-O} and higher.  It requires that @option{-ftree-ccp} is enabled.
  
 +@item -fmerge-bitfields
 +@opindex fmerge-bitfields
 +Combines several adjacent bit-field accesses that copy values
 +from one memory location to another into one single bit-field access.
 +
  @item -ftree-ccp
  @opindex ftree-ccp
  Perform sparse conditional constant propagation (CCP) on trees.  This

Can you mention that it's enabled at level -O2 here?  Also don't forget to
add it to the list of flags enabled by -O2 that appears earlier (@item -O2).
That list is woefully out of date but let's not make it any worse.


-- 
Ryan Hillpsn: dirtyepic_sk
   gcc-porting/toolchain/wxwidgets @ gentoo.org

47C3 6D62 4864 0E49 8E9E  7F92 ED38 BD49 957A 8463


signature.asc
Description: PGP signature

RE: [PATCH] Add a new option -fmerge-bitfields (patch / doc inside)

2014-04-17 Thread Zoran Jovanovic 
Hello,
My apologies for inconvenience.
Removed every appearance of -ftree-bitfield-merge from the patch and fixed an 
issue with unions.
The rest of the patch is the same as before.

Regards,
Zoran Jovanovic

--

Lowering is applied only for bit-fields copy sequences that are merged.
Data structure representing bit-field copy sequences is renamed and reduced in 
size.
Optimization turned on by default for -O2 and higher.
Some comments fixed.

Benchmarking performed on WebKit for Android.
Code size reduction noticed on several files, best examples are:

core/rendering/style/StyleMultiColData (632-520 bytes)
core/platform/graphics/FontDescription (1715-1475 bytes)
core/rendering/style/FillLayer (5069-4513 bytes)
core/rendering/style/StyleRareInheritedData (5618-5346)
core/css/CSSSelectorList(4047-3887)
core/platform/animation/CSSAnimationData (3844-3440 bytes)
core/css/resolver/FontBuilder (13818-13350 bytes)
core/platform/graphics/Font (16447-15975 bytes)


Example:

One of the motivating examples for this work was copy constructor of the class 
which contains bit-fields.

C++ code:
class A
{
public:
A(const A x);
unsigned a : 1;
unsigned b : 2;
unsigned c : 4;
};

A::A(const Ax)
{
a = x.a;
b = x.b;
c = x.c;
}

GIMPLE code without optimization:

  bb 2:
  _3 = x_2(D)-a;
  this_4(D)-a = _3;
  _6 = x_2(D)-b;
  this_4(D)-b = _6;
  _8 = x_2(D)-c;
  this_4(D)-c = _8;
  return;

Optimized GIMPLE code:
  bb 2:
  _10 = x_2(D)-D.1867;
  _11 = BIT_FIELD_REF _10, 7, 0;
  _12 = this_4(D)-D.1867;
  _13 = _12  128;
  _14 = (unsigned char) _11;
  _15 = _13 | _14;
  this_4(D)-D.1867 = _15;
  return;

Generated MIPS32r2 assembly code without optimization:
 lw  $3,0($5)
lbu $2,0($4)
andi$3,$3,0x1
andi$2,$2,0xfe
or  $2,$2,$3
sb  $2,0($4)
lw  $3,0($5)
andi$2,$2,0xf9
andi$3,$3,0x6
or  $2,$2,$3
sb  $2,0($4)
lw  $3,0($5)
andi$2,$2,0x87
andi$3,$3,0x78
or  $2,$2,$3
j   $31
sb  $2,0($4)

Optimized MIPS32r2 assembly code:
lw  $3,0($5)
lbu $2,0($4)
andi$3,$3,0x7f
andi$2,$2,0x80
or  $2,$3,$2
j   $31
sb  $2,0($4)


Algorithm works on basic block level and consists of following 3 major steps:
1. Go through basic block statements list. If there are statement pairs that 
implement copy of bit field content from one memory location to another record 
statements pointers and other necessary data in corresponding data structure.
2. Identify records that represent adjacent bit field accesses and mark them as 
merged.
3. Lower bit-field accesses by using new field size for those that can be 
merged.


New command line option -fmerge-bitfields is introduced.


Tested - passed gcc regression tests for MIPS32r2.


Changelog -

gcc/ChangeLog:
2014-04-16 Zoran Jovanovic (zoran.jovano...@imgtec.com)
  * common.opt (fmerge-bitfields): New option.
  * doc/invoke.texi: Add reference to -fmerge-bitfields.
  * tree-sra.c (lower_bitfields): New function.
  Entry for (-fmerge-bitfields).
  (part_of_union_p): New function.
  (bf_access_candidate_p): New function.
  (lower_bitfield_read): New function.
  (lower_bitfield_write): New function.
  (bitfield_stmt_bfcopy_pair::hash): New function.
  (bitfield_stmt_bfcopy_pair::equal): New function.
  (bitfield_stmt_bfcopy_pair::remove): New function.
  (create_and_insert_bfcopy): New function.
  (get_bit_offset): New function.
  (add_stmt_bfcopy_pair): New function.
  (cmp_bfcopies): New function.
  (get_merged_bit_field_size): New function.
  * dwarf2out.c (simple_type_size_in_bits): Move to tree.c.
  (field_byte_offset): Move declaration to tree.h and make it extern.
  * testsuite/gcc.dg/tree-ssa/bitfldmrg1.c: New test.
  * testsuite/gcc.dg/tree-ssa/bitfldmrg2.c: New test.
  * tree-ssa-sccvn.c (expressions_equal_p): Move to tree.c.
  * tree-ssa-sccvn.h (expressions_equal_p): Move declaration to tree.h.
  * tree.c (expressions_equal_p): Move from tree-ssa-sccvn.c.
  (simple_type_size_in_bits): Move from dwarf2out.c.
  * tree.h (expressions_equal_p): Add declaration.
  (field_byte_offset): Add declaration.

Patch -

diff --git a/gcc/common.opt b/gcc/common.opt
index da275e5..52c7f58 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -2203,6 +2203,10 @@ ftree-sra
 Common Report Var(flag_tree_sra) Optimization
 Perform scalar replacement of aggregates
 
+fmerge-bitfields
+Common Report Var(flag_tree_bitfield_merge) Optimization
+Merge loads and stores of consecutive bitfields
+
 ftree-ter
 Common Report Var(flag_tree_ter) Optimization
 Replace temporary expressions in the SSA-normal pass
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index

RE: [PATCH] Add a new option -fmerge-bitfields (patch / doc inside)

2014-04-17 Thread Zoran Jovanovic 
Hello,
Unfortunately, optimization is limited only to bit-fields that have same 
bit-field representative (DECL_BIT_FIELD_REPRESENTATIVE), and fields from 
different classes do have different representatives.
In given example optimization would merge accesses to x and y bit-fields from 
Base class, but not the access to z from Der class.

Regards,
Zoran
  

From: Daniel Gutson [daniel.gut...@tallertechnologies.com]
Sent: Wednesday, April 16, 2014 4:16 PM
To: Zoran Jovanovic
Cc: Bernhard Reutner-Fischer; Richard Biener; gcc-patches@gcc.gnu.org
Subject: Re: [PATCH] Add a new option -fmerge-bitfields (patch / doc inside)

On Wed, Apr 16, 2014 at 8:38 AM, Zoran Jovanovic
zoran.jovano...@imgtec.com wrote:
 Hello,
 This is new patch version.
 Lowering is applied only for bit-fields copy sequences that are merged.
 Data structure representing bit-field copy sequences is renamed and reduced 
 in size.
 Optimization turned on by default for -O2 and higher.
 Some comments fixed.

 Benchmarking performed on WebKit for Android.
 Code size reduction noticed on several files, best examples are:

 core/rendering/style/StyleMultiColData (632-520 bytes)
 core/platform/graphics/FontDescription (1715-1475 bytes)
 core/rendering/style/FillLayer (5069-4513 bytes)
 core/rendering/style/StyleRareInheritedData (5618-5346)
 core/css/CSSSelectorList(4047-3887)
 core/platform/animation/CSSAnimationData (3844-3440 bytes)
 core/css/resolver/FontBuilder (13818-13350 bytes)
 core/platform/graphics/Font (16447-15975 bytes)


 Example:

 One of the motivating examples for this work was copy constructor of the 
 class which contains bit-fields.

 C++ code:
 class A
 {
 public:
 A(const A x);
 unsigned a : 1;
 unsigned b : 2;
 unsigned c : 4;
 };

 A::A(const Ax)
 {
 a = x.a;
 b = x.b;
 c = x.c;
 }

Very interesting.

Does this work with inheritance too? E.g.

struct Base
{
uint32_t x:1;
uint32_t y:3;

Base(const Base other) { x = other.x; y = other.y; }
};

struct Der : Base
{
Der() = default;
Der(const Der other) : Base(other)
{ z = other.z; }

uint32_t z:9;
};



 GIMPLE code without optimization:

   bb 2:
   _3 = x_2(D)-a;
   this_4(D)-a = _3;
   _6 = x_2(D)-b;
   this_4(D)-b = _6;
   _8 = x_2(D)-c;
   this_4(D)-c = _8;
   return;

 Optimized GIMPLE code:
   bb 2:
   _10 = x_2(D)-D.1867;
   _11 = BIT_FIELD_REF _10, 7, 0;
   _12 = this_4(D)-D.1867;
   _13 = _12  128;
   _14 = (unsigned char) _11;
   _15 = _13 | _14;
   this_4(D)-D.1867 = _15;
   return;

 Generated MIPS32r2 assembly code without optimization:
  lw  $3,0($5)
 lbu $2,0($4)
 andi$3,$3,0x1
 andi$2,$2,0xfe
 or  $2,$2,$3
 sb  $2,0($4)
 lw  $3,0($5)
 andi$2,$2,0xf9
 andi$3,$3,0x6
 or  $2,$2,$3
 sb  $2,0($4)
 lw  $3,0($5)
 andi$2,$2,0x87
 andi$3,$3,0x78
 or  $2,$2,$3
 j   $31
 sb  $2,0($4)

 Optimized MIPS32r2 assembly code:
 lw  $3,0($5)
 lbu $2,0($4)
 andi$3,$3,0x7f
 andi$2,$2,0x80
 or  $2,$3,$2
 j   $31
 sb  $2,0($4)


 Algorithm works on basic block level and consists of following 3 major steps:
 1. Go through basic block statements list. If there are statement pairs that 
 implement copy of bit field content from one memory location to another 
 record statements pointers and other necessary data in corresponding data 
 structure.
 2. Identify records that represent adjacent bit field accesses and mark them 
 as merged.
 3. Lower bit-field accesses by using new field size for those that can be 
 merged.


 New command line option -fmerge-bitfields is introduced.


 Tested - passed gcc regression tests for MIPS32r2.


 Changelog -

 gcc/ChangeLog:
 2014-04-16 Zoran Jovanovic (zoran.jovano...@imgtec.com)
   * common.opt (fmerge-bitfields): New option.
   * doc/invoke.texi: Add reference to -fmerge-bitfields.
   * tree-sra.c (lower_bitfields): New function.
   Entry for (-fmerge-bitfields).
   (bf_access_candidate_p): New function.
   (lower_bitfield_read): New function.
   (lower_bitfield_write): New function.
   (bitfield_stmt_bfcopy_pair::hash): New function.
   (bitfield_stmt_bfcopy_pair::equal): New function.
   (bitfield_stmt_bfcopy_pair::remove): New function.
   (create_and_insert_bfcopy): New function.
   (get_bit_offset): New function.
   (add_stmt_bfcopy_pair): New function.
   (cmp_bfcopies): New function.
   (get_merged_bit_field_size): New function.
   * dwarf2out.c (simple_type_size_in_bits): Move to tree.c.
   (field_byte_offset): Move declaration to tree.h and make it extern.
   * testsuite/gcc.dg/tree-ssa/bitfldmrg1.c: New test.
   * testsuite/gcc.dg/tree-ssa/bitfldmrg2.c: New test.
   * tree-ssa-sccvn.c (expressions_equal_p): Move to tree.c.
   * tree

RE: [PATCH] Add a new option -fmerge-bitfields (patch / doc inside)

2014-04-16 Thread Zoran Jovanovic 
Hello,
This is new patch version. 
Lowering is applied only for bit-fields copy sequences that are merged.
Data structure representing bit-field copy sequences is renamed and reduced in 
size.
Optimization turned on by default for -O2 and higher.
Some comments fixed.

Benchmarking performed on WebKit for Android.
Code size reduction noticed on several files, best examples are:

core/rendering/style/StyleMultiColData (632-520 bytes)
core/platform/graphics/FontDescription (1715-1475 bytes)
core/rendering/style/FillLayer (5069-4513 bytes)
core/rendering/style/StyleRareInheritedData (5618-5346)
core/css/CSSSelectorList(4047-3887)
core/platform/animation/CSSAnimationData (3844-3440 bytes)
core/css/resolver/FontBuilder (13818-13350 bytes)
core/platform/graphics/Font (16447-15975 bytes)


Example:

One of the motivating examples for this work was copy constructor of the class 
which contains bit-fields.

C++ code:
class A
{
public:
A(const A x);
unsigned a : 1;
unsigned b : 2;
unsigned c : 4;
};

A::A(const Ax)
{
a = x.a;
b = x.b;
c = x.c;
}

GIMPLE code without optimization:

  bb 2:
  _3 = x_2(D)-a;
  this_4(D)-a = _3;
  _6 = x_2(D)-b;
  this_4(D)-b = _6;
  _8 = x_2(D)-c;
  this_4(D)-c = _8;
  return;

Optimized GIMPLE code:
  bb 2:
  _10 = x_2(D)-D.1867;
  _11 = BIT_FIELD_REF _10, 7, 0;
  _12 = this_4(D)-D.1867;
  _13 = _12  128;
  _14 = (unsigned char) _11;
  _15 = _13 | _14;
  this_4(D)-D.1867 = _15;
  return;

Generated MIPS32r2 assembly code without optimization:
 lw  $3,0($5)
lbu $2,0($4)
andi$3,$3,0x1
andi$2,$2,0xfe
or  $2,$2,$3
sb  $2,0($4)
lw  $3,0($5)
andi$2,$2,0xf9
andi$3,$3,0x6
or  $2,$2,$3
sb  $2,0($4)
lw  $3,0($5)
andi$2,$2,0x87
andi$3,$3,0x78
or  $2,$2,$3
j   $31
sb  $2,0($4)

Optimized MIPS32r2 assembly code:
lw  $3,0($5)
lbu $2,0($4)
andi$3,$3,0x7f
andi$2,$2,0x80
or  $2,$3,$2
j   $31
sb  $2,0($4)


Algorithm works on basic block level and consists of following 3 major steps:
1. Go through basic block statements list. If there are statement pairs that 
implement copy of bit field content from one memory location to another record 
statements pointers and other necessary data in corresponding data structure.
2. Identify records that represent adjacent bit field accesses and mark them as 
merged.
3. Lower bit-field accesses by using new field size for those that can be 
merged.


New command line option -fmerge-bitfields is introduced.


Tested - passed gcc regression tests for MIPS32r2.


Changelog -

gcc/ChangeLog:
2014-04-16 Zoran Jovanovic (zoran.jovano...@imgtec.com)
  * common.opt (fmerge-bitfields): New option.
  * doc/invoke.texi: Add reference to -fmerge-bitfields.
  * tree-sra.c (lower_bitfields): New function.
  Entry for (-fmerge-bitfields).
  (bf_access_candidate_p): New function.
  (lower_bitfield_read): New function.
  (lower_bitfield_write): New function.
  (bitfield_stmt_bfcopy_pair::hash): New function.
  (bitfield_stmt_bfcopy_pair::equal): New function.
  (bitfield_stmt_bfcopy_pair::remove): New function.
  (create_and_insert_bfcopy): New function.
  (get_bit_offset): New function.
  (add_stmt_bfcopy_pair): New function.
  (cmp_bfcopies): New function.
  (get_merged_bit_field_size): New function.
  * dwarf2out.c (simple_type_size_in_bits): Move to tree.c.
  (field_byte_offset): Move declaration to tree.h and make it extern.
  * testsuite/gcc.dg/tree-ssa/bitfldmrg1.c: New test.
  * testsuite/gcc.dg/tree-ssa/bitfldmrg2.c: New test.
  * tree-ssa-sccvn.c (expressions_equal_p): Move to tree.c.
  * tree-ssa-sccvn.h (expressions_equal_p): Move declaration to tree.h.
  * tree.c (expressions_equal_p): Move from tree-ssa-sccvn.c.
  (simple_type_size_in_bits): Move from dwarf2out.c.
  * tree.h (expressions_equal_p): Add declaration.
  (field_byte_offset): Add declaration.

Patch -

diff --git a/gcc/common.opt b/gcc/common.opt
index da275e5..52c7f58 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -2203,6 +2203,10 @@ ftree-sra
 Common Report Var(flag_tree_sra) Optimization
 Perform scalar replacement of aggregates
 
+fmerge-bitfields
+Common Report Var(flag_tree_bitfield_merge) Optimization
+Merge loads and stores of consecutive bitfields
+
 ftree-ter
 Common Report Var(flag_tree_ter) Optimization
 Replace temporary expressions in the SSA-normal pass
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 3fdfeb9..546638e 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -411,7 +411,7 @@ Objective-C and Objective-C++ Dialects}.
 -fsplit-ivs-in-unroller -fsplit-wide-types -fstack-protector @gol
 -fstack-protector-all -fstack-protector-strong -fstrict-aliasing @gol
 -fstrict-overflow -fthread-jumps -ftracer -ftree-bit-ccp @gol

Re: [PATCH] Add a new option -fmerge-bitfields (patch / doc inside)

2014-04-16 Thread Bernhard Reutner-Fischer 
On 16 April 2014 13:38, Zoran Jovanovic zoran.jovano...@imgtec.com wrote:
 Hello,
 This is new patch version.

The comment from the previous iteration still holds true:

 +@item -fbitfield-merge

you are talking about '-fmerge-bitfields' up until here.
Please fix all occurances of bitfield-merge, both in the docs as well
as in the gcc.dg/tree-ssa/bitfldmrg2.c testcase -- how did that pass anyway
as that option is presumably not recognized? :)

thanks,

Re: [PATCH] Add a new option -fmerge-bitfields (patch / doc inside)

2014-04-16 Thread Daniel Gutson 
On Wed, Apr 16, 2014 at 8:38 AM, Zoran Jovanovic
zoran.jovano...@imgtec.com wrote:
 Hello,
 This is new patch version.
 Lowering is applied only for bit-fields copy sequences that are merged.
 Data structure representing bit-field copy sequences is renamed and reduced 
 in size.
 Optimization turned on by default for -O2 and higher.
 Some comments fixed.

 Benchmarking performed on WebKit for Android.
 Code size reduction noticed on several files, best examples are:

 core/rendering/style/StyleMultiColData (632-520 bytes)
 core/platform/graphics/FontDescription (1715-1475 bytes)
 core/rendering/style/FillLayer (5069-4513 bytes)
 core/rendering/style/StyleRareInheritedData (5618-5346)
 core/css/CSSSelectorList(4047-3887)
 core/platform/animation/CSSAnimationData (3844-3440 bytes)
 core/css/resolver/FontBuilder (13818-13350 bytes)
 core/platform/graphics/Font (16447-15975 bytes)


 Example:

 One of the motivating examples for this work was copy constructor of the 
 class which contains bit-fields.

 C++ code:
 class A
 {
 public:
 A(const A x);
 unsigned a : 1;
 unsigned b : 2;
 unsigned c : 4;
 };

 A::A(const Ax)
 {
 a = x.a;
 b = x.b;
 c = x.c;
 }

Very interesting.

Does this work with inheritance too? E.g.

struct Base
{
uint32_t x:1;
uint32_t y:3;

Base(const Base other) { x = other.x; y = other.y; }
};

struct Der : Base
{
Der() = default;
Der(const Der other) : Base(other)
{ z = other.z; }

uint32_t z:9;
};



 GIMPLE code without optimization:

   bb 2:
   _3 = x_2(D)-a;
   this_4(D)-a = _3;
   _6 = x_2(D)-b;
   this_4(D)-b = _6;
   _8 = x_2(D)-c;
   this_4(D)-c = _8;
   return;

 Optimized GIMPLE code:
   bb 2:
   _10 = x_2(D)-D.1867;
   _11 = BIT_FIELD_REF _10, 7, 0;
   _12 = this_4(D)-D.1867;
   _13 = _12  128;
   _14 = (unsigned char) _11;
   _15 = _13 | _14;
   this_4(D)-D.1867 = _15;
   return;

 Generated MIPS32r2 assembly code without optimization:
  lw  $3,0($5)
 lbu $2,0($4)
 andi$3,$3,0x1
 andi$2,$2,0xfe
 or  $2,$2,$3
 sb  $2,0($4)
 lw  $3,0($5)
 andi$2,$2,0xf9
 andi$3,$3,0x6
 or  $2,$2,$3
 sb  $2,0($4)
 lw  $3,0($5)
 andi$2,$2,0x87
 andi$3,$3,0x78
 or  $2,$2,$3
 j   $31
 sb  $2,0($4)

 Optimized MIPS32r2 assembly code:
 lw  $3,0($5)
 lbu $2,0($4)
 andi$3,$3,0x7f
 andi$2,$2,0x80
 or  $2,$3,$2
 j   $31
 sb  $2,0($4)


 Algorithm works on basic block level and consists of following 3 major steps:
 1. Go through basic block statements list. If there are statement pairs that 
 implement copy of bit field content from one memory location to another 
 record statements pointers and other necessary data in corresponding data 
 structure.
 2. Identify records that represent adjacent bit field accesses and mark them 
 as merged.
 3. Lower bit-field accesses by using new field size for those that can be 
 merged.


 New command line option -fmerge-bitfields is introduced.


 Tested - passed gcc regression tests for MIPS32r2.


 Changelog -

 gcc/ChangeLog:
 2014-04-16 Zoran Jovanovic (zoran.jovano...@imgtec.com)
   * common.opt (fmerge-bitfields): New option.
   * doc/invoke.texi: Add reference to -fmerge-bitfields.
   * tree-sra.c (lower_bitfields): New function.
   Entry for (-fmerge-bitfields).
   (bf_access_candidate_p): New function.
   (lower_bitfield_read): New function.
   (lower_bitfield_write): New function.
   (bitfield_stmt_bfcopy_pair::hash): New function.
   (bitfield_stmt_bfcopy_pair::equal): New function.
   (bitfield_stmt_bfcopy_pair::remove): New function.
   (create_and_insert_bfcopy): New function.
   (get_bit_offset): New function.
   (add_stmt_bfcopy_pair): New function.
   (cmp_bfcopies): New function.
   (get_merged_bit_field_size): New function.
   * dwarf2out.c (simple_type_size_in_bits): Move to tree.c.
   (field_byte_offset): Move declaration to tree.h and make it extern.
   * testsuite/gcc.dg/tree-ssa/bitfldmrg1.c: New test.
   * testsuite/gcc.dg/tree-ssa/bitfldmrg2.c: New test.
   * tree-ssa-sccvn.c (expressions_equal_p): Move to tree.c.
   * tree-ssa-sccvn.h (expressions_equal_p): Move declaration to tree.h.
   * tree.c (expressions_equal_p): Move from tree-ssa-sccvn.c.
   (simple_type_size_in_bits): Move from dwarf2out.c.
   * tree.h (expressions_equal_p): Add declaration.
   (field_byte_offset): Add declaration.

 Patch -

 diff --git a/gcc/common.opt b/gcc/common.opt
 index da275e5..52c7f58 100644
 --- a/gcc/common.opt
 +++ b/gcc/common.opt
 @@ -2203,6 +2203,10 @@ ftree-sra
  Common Report Var(flag_tree_sra) Optimization
  Perform scalar replacement of aggregates

 +fmerge-bitfields
 +Common Report Var(flag_tree_bitfield_merge) Optimization
 +Merge loads and stores of consecutive bitfields
 +