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[PATCH][RFC][1/2] Bitfield lowering, add BIT_FIELD_EXPR
- From: Richard Guenther <rguenther at suse dot de>
- To: gcc-patches at gcc dot gnu dot org
- Date: Thu, 16 Jun 2011 13:35:17 +0200 (CEST)
- Subject: [PATCH][RFC][1/2] Bitfield lowering, add BIT_FIELD_EXPR
This is a (possible) pre-requesite for the bitfield lowering patch,
taken from the old mem-ref branch. It introduces BIT_FIELD_EXPR
which can be used to do bitfield composition.
BIT_FIELD_EXPR <a, b, C1, C2> is equivalent to computing
a & ~((1 << C1 - 1) << C2) | ((b << C2) & (1 << C1 = 1)), thus
inserting b of width C1 at the bitfield position C2 in a, returning
the new value. This allows translating
BIT_FIELD_REF <a, C1, C2> = b;
to
a = BIT_FIELD_EXPR <a, b, C1, C2>;
which avoids partial definitions of a (thus, BIT_FIELD_EXPR is
similar to COMPLEX_EXPR). BIT_FIELD_EXPR is supposed to work
on registers only.
Comments welcome, esp. on how to avoid introducing quaternary
RHS on gimple stmts (or using a GIMPLE_SINGLE_RHS as the patch does).
Folders/combiners are missing to handle some of the easy
BIT_FIELD_REF / BIT_FIELD_EXPR cases, as well as eventually
re-writing shift/mask operations to BIT_FIELD_REF/EXPR.
Richard.
2011-06-16 Richard Guenther <rguenther@suse.de>
* expr.c (expand_expr_real_1): Handle BIT_FIELD_EXPR.
* fold-const.c (operand_equal_p): Likewise.
(build_bit_mask): New function.
(fold_quaternary_loc): Likewise.
(fold): Call it.
(fold_build4_stat_loc): New function.
* gimplify.c (gimplify_expr): Handle BIT_FIELD_EXPR.
* tree-inline.c (estimate_operator_cost): Likewise.
* tree-pretty-print.c (dump_generic_node): Likewise.
* tree-ssa-operands.c (get_expr_operands): Likewise.
* tree.def (BIT_FIELD_EXPR): New tree code.
* tree.h (build_bit_mask): Declare.
(fold_quaternary): Define.
(fold_quaternary_loc): Declare.
(fold_build4): Define.
(fold_build4_loc): Likewise.
(fold_build4_stat_loc): Declare.
* gimple.c (gimple_rhs_class_table): Handle BIT_FIELD_EXPR.
Index: trunk/gcc/expr.c
===================================================================
*** trunk.orig/gcc/expr.c 2011-06-15 13:27:40.000000000 +0200
--- trunk/gcc/expr.c 2011-06-15 15:08:41.000000000 +0200
*************** expand_expr_real_1 (tree exp, rtx target
*** 8680,8685 ****
--- 8680,8708 ----
return expand_constructor (exp, target, modifier, false);
+ case BIT_FIELD_EXPR:
+ {
+ unsigned bitpos = (unsigned) TREE_INT_CST_LOW (TREE_OPERAND (exp, 3));
+ unsigned bitsize = (unsigned) TREE_INT_CST_LOW (TREE_OPERAND (exp, 2));
+ tree bits, mask;
+ if (BYTES_BIG_ENDIAN)
+ bitpos = TYPE_PRECISION (type) - bitsize - bitpos;
+ /* build a mask to mask/clear the bits in the word. */
+ mask = build_bit_mask (type, bitsize, bitpos);
+ /* extend the bits to the word type, shift them to the right
+ place and mask the bits. */
+ bits = fold_convert (type, TREE_OPERAND (exp, 1));
+ bits = fold_build2 (BIT_AND_EXPR, type,
+ fold_build2 (LSHIFT_EXPR, type,
+ bits, size_int (bitpos)), mask);
+ /* switch to clear mask and do the composition. */
+ mask = fold_build1 (BIT_NOT_EXPR, type, mask);
+ return expand_normal (fold_build2 (BIT_IOR_EXPR, type,
+ fold_build2 (BIT_AND_EXPR, type,
+ TREE_OPERAND (exp, 0), mask),
+ bits));
+ }
+
case TARGET_MEM_REF:
{
addr_space_t as = TYPE_ADDR_SPACE (TREE_TYPE (exp));
Index: trunk/gcc/fold-const.c
===================================================================
*** trunk.orig/gcc/fold-const.c 2011-06-15 14:51:31.000000000 +0200
--- trunk/gcc/fold-const.c 2011-06-15 15:33:04.000000000 +0200
*************** operand_equal_p (const_tree arg0, const_
*** 2667,2672 ****
--- 2667,2675 ----
case DOT_PROD_EXPR:
return OP_SAME (0) && OP_SAME (1) && OP_SAME (2);
+ case BIT_FIELD_EXPR:
+ return OP_SAME (0) && OP_SAME (1) && OP_SAME (2) && OP_SAME (3);
+
default:
return 0;
}
*************** contains_label_p (tree st)
*** 13230,13235 ****
--- 13233,13251 ----
(walk_tree_without_duplicates (&st, contains_label_1 , NULL) != NULL_TREE);
}
+ /* Builds and returns a mask of integral type TYPE for masking out
+ BITSIZE bits at bit position BITPOS in a word of type TYPE.
+ The mask has the bits set from bit BITPOS to BITPOS + BITSIZE - 1. */
+
+ tree
+ build_bit_mask (tree type, unsigned int bitsize, unsigned int bitpos)
+ {
+ tree mask = double_int_to_tree (type, double_int_mask (bitsize));
+ mask = const_binop (LSHIFT_EXPR, mask, size_int (bitpos));
+
+ return mask;
+ }
+
/* Fold a ternary expression of code CODE and type TYPE with operands
OP0, OP1, and OP2. Return the folded expression if folding is
successful. Otherwise, return NULL_TREE. */
*************** fold_ternary_loc (location_t loc, enum t
*** 13591,13596 ****
--- 13607,13685 ----
} /* switch (code) */
}
+ /* Fold a quaternary expression of code CODE and type TYPE with operands
+ OP0, OP1, OP2, and OP3. Return the folded expression if folding is
+ successful. Otherwise, return NULL_TREE. */
+
+ tree
+ fold_quaternary_loc (location_t loc, enum tree_code code, tree type,
+ tree op0, tree op1, tree op2, tree op3)
+ {
+ tree arg0 = NULL_TREE, arg1 = NULL_TREE;
+ enum tree_code_class kind = TREE_CODE_CLASS (code);
+
+ gcc_assert (IS_EXPR_CODE_CLASS (kind)
+ && TREE_CODE_LENGTH (code) == 4);
+
+ /* Strip any conversions that don't change the mode. This is safe
+ for every expression, except for a comparison expression because
+ its signedness is derived from its operands. So, in the latter
+ case, only strip conversions that don't change the signedness.
+
+ Note that this is done as an internal manipulation within the
+ constant folder, in order to find the simplest representation of
+ the arguments so that their form can be studied. In any cases,
+ the appropriate type conversions should be put back in the tree
+ that will get out of the constant folder. */
+ if (op0)
+ {
+ arg0 = op0;
+ STRIP_NOPS (arg0);
+ }
+
+ if (op1)
+ {
+ arg1 = op1;
+ STRIP_NOPS (arg1);
+ }
+
+ switch (code)
+ {
+ case BIT_FIELD_EXPR:
+ /* Constant fold BIT_FIELD_EXPR. */
+ if (TREE_CODE (arg0) == INTEGER_CST
+ || TREE_CODE (arg1) == INTEGER_CST)
+ {
+ unsigned bitpos = (unsigned) TREE_INT_CST_LOW (op3);
+ unsigned bitsize = (unsigned) TREE_INT_CST_LOW (op2);
+ tree bits, mask;
+ if (BYTES_BIG_ENDIAN)
+ bitpos = TYPE_PRECISION (type) - bitsize - bitpos;
+ /* build a mask to mask/clear the bits in the word. */
+ mask = build_bit_mask (type, bitsize, bitpos);
+ /* extend the bits to the word type, shift them to the right
+ place and mask the bits. */
+ bits = fold_convert_loc (loc, type, arg1);
+ bits = fold_build2_loc (loc, BIT_AND_EXPR, type,
+ fold_build2_loc (loc, LSHIFT_EXPR, type,
+ bits, size_int (bitpos)),
+ mask);
+ /* switch to clear mask and do the composition. */
+ mask = fold_build1_loc (loc, BIT_NOT_EXPR, type, mask);
+ return fold_build2_loc (loc, BIT_IOR_EXPR, type,
+ fold_build2_loc (loc, BIT_AND_EXPR, type,
+ fold_convert (type, arg0),
+ mask),
+ bits);
+ }
+
+ return NULL_TREE;
+
+ default:
+ return NULL_TREE;
+ }
+ }
+
/* Perform constant folding and related simplification of EXPR.
The related simplifications include x*1 => x, x*0 => 0, etc.,
and application of the associative law.
*************** fold (tree expr)
*** 13632,13638 ****
if (IS_EXPR_CODE_CLASS (kind))
{
tree type = TREE_TYPE (t);
! tree op0, op1, op2;
switch (TREE_CODE_LENGTH (code))
{
--- 13721,13727 ----
if (IS_EXPR_CODE_CLASS (kind))
{
tree type = TREE_TYPE (t);
! tree op0, op1, op2, op3;
switch (TREE_CODE_LENGTH (code))
{
*************** fold (tree expr)
*** 13651,13656 ****
--- 13740,13752 ----
op2 = TREE_OPERAND (t, 2);
tem = fold_ternary_loc (loc, code, type, op0, op1, op2);
return tem ? tem : expr;
+ case 4:
+ op0 = TREE_OPERAND (t, 0);
+ op1 = TREE_OPERAND (t, 1);
+ op2 = TREE_OPERAND (t, 2);
+ op3 = TREE_OPERAND (t, 3);
+ tem = fold_quaternary_loc (loc, code, type, op0, op1, op2, op3);
+ return tem ? tem : expr;
default:
break;
}
*************** fold_build3_stat_loc (location_t loc, en
*** 14107,14112 ****
--- 14203,14294 ----
return tem;
}
+ /* Fold a quaternary tree expression with code CODE of type TYPE with
+ operands OP0, OP1, OP2, and OP3. Return a folded expression if
+ successful. Otherwise, return a tree expression with code CODE of
+ type TYPE with operands OP0, OP1, OP2, and OP3. */
+
+ tree
+ fold_build4_stat_loc (location_t loc, enum tree_code code, tree type,
+ tree op0, tree op1, tree op2, tree op3 MEM_STAT_DECL)
+ {
+ tree tem;
+ #ifdef ENABLE_FOLD_CHECKING
+ unsigned char checksum_before_op0[16],
+ checksum_before_op1[16],
+ checksum_before_op2[16],
+ checksum_before_op3[16],
+ checksum_after_op0[16],
+ checksum_after_op1[16],
+ checksum_after_op2[16];
+ checksum_after_op3[16];
+ struct md5_ctx ctx;
+ htab_t ht;
+
+ ht = htab_create (32, htab_hash_pointer, htab_eq_pointer, NULL);
+ md5_init_ctx (&ctx);
+ fold_checksum_tree (op0, &ctx, ht);
+ md5_finish_ctx (&ctx, checksum_before_op0);
+ htab_empty (ht);
+
+ md5_init_ctx (&ctx);
+ fold_checksum_tree (op1, &ctx, ht);
+ md5_finish_ctx (&ctx, checksum_before_op1);
+ htab_empty (ht);
+
+ md5_init_ctx (&ctx);
+ fold_checksum_tree (op2, &ctx, ht);
+ md5_finish_ctx (&ctx, checksum_before_op2);
+ htab_empty (ht);
+
+ md5_init_ctx (&ctx);
+ fold_checksum_tree (op3, &ctx, ht);
+ md5_finish_ctx (&ctx, checksum_before_op3);
+ htab_empty (ht);
+ #endif
+
+ gcc_assert (TREE_CODE_CLASS (code) != tcc_vl_exp);
+ tem = fold_quaternary_loc (loc, code, type, op0, op1, op2, op3);
+ if (!tem)
+ tem = build4_stat_loc (loc, code, type, op0, op1, op2, op3 PASS_MEM_STAT);
+
+ #ifdef ENABLE_FOLD_CHECKING
+ md5_init_ctx (&ctx);
+ fold_checksum_tree (op0, &ctx, ht);
+ md5_finish_ctx (&ctx, checksum_after_op0);
+ htab_empty (ht);
+
+ if (memcmp (checksum_before_op0, checksum_after_op0, 16))
+ fold_check_failed (op0, tem);
+
+ md5_init_ctx (&ctx);
+ fold_checksum_tree (op1, &ctx, ht);
+ md5_finish_ctx (&ctx, checksum_after_op1);
+ htab_empty (ht);
+
+ if (memcmp (checksum_before_op1, checksum_after_op1, 16))
+ fold_check_failed (op1, tem);
+
+ md5_init_ctx (&ctx);
+ fold_checksum_tree (op2, &ctx, ht);
+ md5_finish_ctx (&ctx, checksum_after_op2);
+ htab_delete (ht);
+
+ if (memcmp (checksum_before_op2, checksum_after_op2, 16))
+ fold_check_failed (op2, tem);
+
+ md5_init_ctx (&ctx);
+ fold_checksum_tree (op3, &ctx, ht);
+ md5_finish_ctx (&ctx, checksum_after_op3);
+ htab_delete (ht);
+
+ if (memcmp (checksum_before_op3, checksum_after_op3, 16))
+ fold_check_failed (op3, tem);
+ #endif
+ return tem;
+ }
+
+
/* Fold a CALL_EXPR expression of type TYPE with operands FN and NARGS
arguments in ARGARRAY, and a null static chain.
Return a folded expression if successful. Otherwise, return a CALL_EXPR
Index: trunk/gcc/gimplify.c
===================================================================
*** trunk.orig/gcc/gimplify.c 2011-06-10 13:28:11.000000000 +0200
--- trunk/gcc/gimplify.c 2011-06-15 15:05:55.000000000 +0200
*************** gimplify_expr (tree *expr_p, gimple_seq
*** 7239,7244 ****
--- 7239,7248 ----
/* Classified as tcc_expression. */
goto expr_3;
+ case BIT_FIELD_EXPR:
+ /* Arguments 3 and 4 are constants. */
+ goto expr_2;
+
case POINTER_PLUS_EXPR:
/* Convert ((type *)A)+offset into &A->field_of_type_and_offset.
The second is gimple immediate saving a need for extra statement.
Index: trunk/gcc/tree-inline.c
===================================================================
*** trunk.orig/gcc/tree-inline.c 2011-06-07 14:41:22.000000000 +0200
--- trunk/gcc/tree-inline.c 2011-06-15 14:56:09.000000000 +0200
*************** estimate_operator_cost (enum tree_code c
*** 3357,3362 ****
--- 3357,3366 ----
return weights->div_mod_cost;
return 1;
+ /* Bit-field insertion needs several shift and mask operations. */
+ case BIT_FIELD_EXPR:
+ return 3;
+
default:
/* We expect a copy assignment with no operator. */
gcc_assert (get_gimple_rhs_class (code) == GIMPLE_SINGLE_RHS);
Index: trunk/gcc/tree-pretty-print.c
===================================================================
*** trunk.orig/gcc/tree-pretty-print.c 2011-06-07 14:41:22.000000000 +0200
--- trunk/gcc/tree-pretty-print.c 2011-06-15 15:07:05.000000000 +0200
*************** dump_generic_node (pretty_printer *buffe
*** 1217,1222 ****
--- 1217,1234 ----
pp_string (buffer, ">");
break;
+ case BIT_FIELD_EXPR:
+ pp_string (buffer, "BIT_FIELD_EXPR <");
+ dump_generic_node (buffer, TREE_OPERAND (node, 0), spc, flags, false);
+ pp_string (buffer, ", ");
+ dump_generic_node (buffer, TREE_OPERAND (node, 1), spc, flags, false);
+ pp_string (buffer, ", ");
+ dump_generic_node (buffer, TREE_OPERAND (node, 2), spc, flags, false);
+ pp_string (buffer, ", ");
+ dump_generic_node (buffer, TREE_OPERAND (node, 3), spc, flags, false);
+ pp_string (buffer, ">");
+ break;
+
case ARRAY_REF:
case ARRAY_RANGE_REF:
op0 = TREE_OPERAND (node, 0);
Index: trunk/gcc/tree-ssa-operands.c
===================================================================
*** trunk.orig/gcc/tree-ssa-operands.c 2011-04-18 11:06:42.000000000 +0200
--- trunk/gcc/tree-ssa-operands.c 2011-06-15 14:54:12.000000000 +0200
*************** get_expr_operands (gimple stmt, tree *ex
*** 974,979 ****
--- 974,984 ----
get_expr_operands (stmt, &TREE_OPERAND (expr, 0), flags);
return;
+ case BIT_FIELD_EXPR:
+ gcc_assert (TREE_CODE (TREE_OPERAND (expr, 2)) == INTEGER_CST
+ && TREE_CODE (TREE_OPERAND (expr, 3)) == INTEGER_CST);
+ /* Fallthru. */
+
case TRUTH_AND_EXPR:
case TRUTH_OR_EXPR:
case TRUTH_XOR_EXPR:
Index: trunk/gcc/tree.def
===================================================================
*** trunk.orig/gcc/tree.def 2011-05-11 11:09:42.000000000 +0200
--- trunk/gcc/tree.def 2011-06-15 14:53:17.000000000 +0200
*************** DEFTREECODE (ADDR_EXPR, "addr_expr", tcc
*** 784,789 ****
--- 784,801 ----
descriptor of type ptr_mode. */
DEFTREECODE (FDESC_EXPR, "fdesc_expr", tcc_expression, 2)
+ /* Given a word, a value and a bitfield position and size within
+ the word, produce the value that results if replacing the
+ described parts of word with value.
+ Operand 0 is a tree for the word of integral type;
+ Operand 1 is a tree for the value of integral type;
+ Operand 2 is a tree giving the constant number of bits being
+ referenced which is less or equal to the precision of the value;
+ Operand 3 is a tree giving the constant position of the first referenced
+ bit such that the sum of operands 2 and 3 is less than or equal to the
+ precision of the word. */
+ DEFTREECODE (BIT_FIELD_EXPR, "bitfield_expr", tcc_expression, 4)
+
/* Given two real or integer operands of the same type,
returns a complex value of the corresponding complex type. */
DEFTREECODE (COMPLEX_EXPR, "complex_expr", tcc_binary, 2)
Index: trunk/gcc/tree.h
===================================================================
*** trunk.orig/gcc/tree.h 2011-06-15 13:27:06.000000000 +0200
--- trunk/gcc/tree.h 2011-06-15 15:19:59.000000000 +0200
*************** extern bool is_typedef_decl (tree x);
*** 5091,5096 ****
--- 5091,5097 ----
extern bool typedef_variant_p (tree);
extern bool auto_var_in_fn_p (const_tree, const_tree);
extern tree build_low_bits_mask (tree, unsigned);
+ extern tree build_bit_mask (tree type, unsigned int, unsigned int);
extern tree tree_strip_nop_conversions (tree);
extern tree tree_strip_sign_nop_conversions (tree);
extern tree lhd_gcc_personality (void);
*************** extern tree fold_binary_loc (location_t,
*** 5147,5152 ****
--- 5148,5156 ----
#define fold_ternary(CODE,T1,T2,T3,T4)\
fold_ternary_loc (UNKNOWN_LOCATION, CODE, T1, T2, T3, T4)
extern tree fold_ternary_loc (location_t, enum tree_code, tree, tree, tree, tree);
+ #define fold_quaternary(CODE,T1,T2,T3,T4,T5)\
+ fold_quaternary_loc (UNKNOWN_LOCATION, CODE, T1, T2, T3, T4, T5)
+ extern tree fold_quaternary_loc (location_t, enum tree_code, tree, tree, tree, tree, tree);
#define fold_build1(c,t1,t2)\
fold_build1_stat_loc (UNKNOWN_LOCATION, c, t1, t2 MEM_STAT_INFO)
#define fold_build1_loc(l,c,t1,t2)\
*************** extern tree fold_build2_stat_loc (locati
*** 5165,5170 ****
--- 5169,5180 ----
fold_build3_stat_loc (l, c, t1, t2, t3, t4 MEM_STAT_INFO)
extern tree fold_build3_stat_loc (location_t, enum tree_code, tree, tree, tree,
tree MEM_STAT_DECL);
+ #define fold_build4(c,t1,t2,t3,t4,t5)\
+ fold_build4_stat_loc (UNKNOWN_LOCATION, c, t1, t2, t3, t4, t5 MEM_STAT_INFO)
+ #define fold_build4_loc(l,c,t1,t2,t3,t4,t5)\
+ fold_build4_stat_loc (l, c, t1, t2, t3, t4, t5 MEM_STAT_INFO)
+ extern tree fold_build4_stat_loc (location_t, enum tree_code, tree, tree, tree,
+ tree, tree MEM_STAT_DECL);
extern tree fold_build1_initializer_loc (location_t, enum tree_code, tree, tree);
extern tree fold_build2_initializer_loc (location_t, enum tree_code, tree, tree, tree);
extern tree fold_build3_initializer_loc (location_t, enum tree_code, tree, tree, tree, tree);
Index: trunk/gcc/gimple.c
===================================================================
*** trunk.orig/gcc/gimple.c 2011-06-15 15:33:04.000000000 +0200
--- trunk/gcc/gimple.c 2011-06-15 15:33:54.000000000 +0200
*************** get_gimple_rhs_num_ops (enum tree_code c
*** 2599,2605 ****
|| (SYM) == ADDR_EXPR \
|| (SYM) == WITH_SIZE_EXPR \
|| (SYM) == SSA_NAME \
! || (SYM) == VEC_COND_EXPR) ? GIMPLE_SINGLE_RHS \
: GIMPLE_INVALID_RHS),
#define END_OF_BASE_TREE_CODES (unsigned char) GIMPLE_INVALID_RHS,
--- 2599,2606 ----
|| (SYM) == ADDR_EXPR \
|| (SYM) == WITH_SIZE_EXPR \
|| (SYM) == SSA_NAME \
! || (SYM) == VEC_COND_EXPR \
! || (SYM) == BIT_FIELD_EXPR) ? GIMPLE_SINGLE_RHS \
: GIMPLE_INVALID_RHS),
#define END_OF_BASE_TREE_CODES (unsigned char) GIMPLE_INVALID_RHS,