OpenE2K/gcc
2
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

re PR tree-optimization/14846 ([tree-ssa] don't use a shift in A & CST_POWER_OF_2 == 0 until very late in tree-ssa optimizations)

Browse Source 
PR tree-optimization/14846
	* fold-const.c (fold_single_bit_test_into_sign_test): New,
	split out from ...
	(fold_single_bit_test): ... here.
	(fold_binary): Call fold_single_bit_test_into_sign_test
	instead of fold_single_bit_test.

From-SVN: r98482
This commit is contained in:
Kazu Hirata 2005-04-21 00:39:22 +00:00 committed by Kazu Hirata
parent fcda200251
commit a94400fda3
2 changed files with 53 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
gcc/ChangeLog
View File

@ -1,3 +1,12 @@
2005-04-21 Kazu Hirata <kazu@cs.umass.edu>
PR tree-optimization/14846
* fold-const.c (fold_single_bit_test_into_sign_test): New,
split out from ...
(fold_single_bit_test): ... here.
(fold_binary): Call fold_single_bit_test_into_sign_test
instead of fold_single_bit_test.
2005-04-20 James E Wilson <wilson@specifixinc.com>
PR c++/20805

62
gcc/fold-const.c
View File

@ -5928,6 +5928,40 @@ fold_div_compare (enum tree_code code, tree type, tree arg0, tree arg1)
}
/* If CODE with arguments ARG0 and ARG1 represents a single bit
equality/inequality test, then return a simplified form of the test
using a sign testing. Otherwise return NULL. TYPE is the desired
result type. */
static tree
fold_single_bit_test_into_sign_test (enum tree_code code, tree arg0, tree arg1,
tree result_type)
{
/* If this is testing a single bit, we can optimize the test. */
if ((code == NE_EXPR || code == EQ_EXPR)
&& TREE_CODE (arg0) == BIT_AND_EXPR && integer_zerop (arg1)
&& integer_pow2p (TREE_OPERAND (arg0, 1)))
{
/* If we have (A & C) != 0 where C is the sign bit of A, convert
this into A < 0. Similarly for (A & C) == 0 into A >= 0. */
tree arg00 = sign_bit_p (TREE_OPERAND (arg0, 0), TREE_OPERAND (arg0, 1));
if (arg00 != NULL_TREE
/* This is only a win if casting to a signed type is cheap,
i.e. when arg00's type is not a partial mode. */
&& TYPE_PRECISION (TREE_TYPE (arg00))
== GET_MODE_BITSIZE (TYPE_MODE (TREE_TYPE (arg00))))
{
tree stype = lang_hooks.types.signed_type (TREE_TYPE (arg00));
return fold_build2 (code == EQ_EXPR ? GE_EXPR : LT_EXPR,
result_type, fold_convert (stype, arg00),
fold_convert (stype, integer_zero_node));
}
}
return NULL_TREE;
}
/* If CODE with arguments ARG0 and ARG1 represents a single bit
equality/inequality test, then return a simplified form of
the test using shifts and logical operations. Otherwise return
@ -5948,22 +5982,14 @@ fold_single_bit_test (enum tree_code code, tree arg0, tree arg1,
enum machine_mode operand_mode = TYPE_MODE (type);
int ops_unsigned;
tree signed_type, unsigned_type, intermediate_type;
tree arg00;
tree tem;
/* If we have (A & C) != 0 where C is the sign bit of A, convert
this into A < 0. Similarly for (A & C) == 0 into A >= 0. */
arg00 = sign_bit_p (TREE_OPERAND (arg0, 0), TREE_OPERAND (arg0, 1));
if (arg00 != NULL_TREE
/* This is only a win if casting to a signed type is cheap,
i.e. when arg00's type is not a partial mode. */
&& TYPE_PRECISION (TREE_TYPE (arg00))
== GET_MODE_BITSIZE (TYPE_MODE (TREE_TYPE (arg00))))
{
tree stype = lang_hooks.types.signed_type (TREE_TYPE (arg00));
return fold_build2 (code == EQ_EXPR ? GE_EXPR : LT_EXPR,
result_type, fold_convert (stype, arg00),
fold_convert (stype, integer_zero_node));
}
/* First, see if we can fold the single bit test into a sign-bit
test. */
tem = fold_single_bit_test_into_sign_test (code, arg0, arg1,
result_type);
if (tem)
return tem;
/* Otherwise we have (A & C) != 0 where C is a single bit,
convert that into ((A >> C2) & 1). Where C2 = log2(C).
@ -9447,9 +9473,9 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
arg0, fold_convert (TREE_TYPE (arg0),
integer_zero_node));
/* If we have (A & C) != 0 or (A & C) == 0 and C is a power of
2, then fold the expression into shifts and logical operations. */
tem = fold_single_bit_test (code, arg0, arg1, type);
/* If we have (A & C) != 0 or (A & C) == 0 and C is the sign
bit, then fold the expression into A < 0 or A >= 0. */
tem = fold_single_bit_test_into_sign_test (code, arg0, arg1, type);
if (tem)
return tem;