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fold-const.c (fold_binary_loc): Fold (X * CST1) & CST2 to zero or to (X * CST1) & CST2' when... 

2012-05-08  Richard Guenther  <rguenther@suse.de>

	* fold-const.c (fold_binary_loc): Fold (X * CST1) & CST2
	to zero or to (X * CST1) & CST2' when CST1 has trailing zeros.

	* gcc.dg/fold-bitand-4.c: New testcase.

From-SVN: r187280
This commit is contained in:
Richard Guenther 2012-05-08 12:50:18 +00:00 committed by Richard Biener
parent 04d170d214
commit ad9fc55abd
4 changed files with 49 additions and 0 deletions
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5
gcc/ChangeLog
View File

@ -1,3 +1,8 @@
2012-05-08 Richard Guenther <rguenther@suse.de>
* fold-const.c (fold_binary_loc): Fold (X * CST1) & CST2
to zero or to (X * CST1) & CST2' when CST1 has trailing zeros.
2012-05-08 Georg-Johann Lay <avr@gjlay.de>
* Makefile.in (TEXI_GCC_FILES): Add avr-mmcu.texi.

24
gcc/fold-const.c
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@ -11449,6 +11449,30 @@ fold_binary_loc (location_t loc,
return fold_convert_loc (loc, type, arg0);
}
/* Fold (X * CST1) & CST2 to zero if we can, or drop known zero
bits from CST2. */
if (TREE_CODE (arg1) == INTEGER_CST
&& TREE_CODE (arg0) == MULT_EXPR
&& TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST)
{
int arg1tz
= double_int_ctz (tree_to_double_int (TREE_OPERAND (arg0, 1)));
if (arg1tz > 0)
{
double_int arg1mask, masked;
arg1mask = double_int_not (double_int_mask (arg1tz));
arg1mask = double_int_ext (arg1mask, TYPE_PRECISION (type),
TYPE_UNSIGNED (type));
masked = double_int_and (arg1mask, tree_to_double_int (arg1));
if (double_int_zero_p (masked))
return omit_two_operands_loc (loc, type, build_zero_cst (type),
arg0, arg1);
else if (!double_int_equal_p (masked, tree_to_double_int (arg1)))
return fold_build2_loc (loc, code, type, op0,
double_int_to_tree (type, masked));
}
}
/* For constants M and N, if M == (1LL << cst) - 1 && (N & M) == M,
((A & N) + B) & M -> (A + B) & M
Similarly if (N & M) == 0,

4
gcc/testsuite/ChangeLog
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@ -1,3 +1,7 @@
2012-05-08 Richard Guenther <rguenther@suse.de>
* gcc.dg/fold-bitand-4.c: New testcase.
2012-05-08 Dehao Chen <dehao@google.com>
* gcc.dg/predict-1.c: Check if LOOP_IV_COMPARE static predict

16
gcc/testsuite/gcc.dg/fold-bitand-4.c Normal file
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@ -0,0 +1,16 @@
/* { dg-do compile } */
/* { dg-options "-O -fdump-tree-original" } */
int foo (int i)
{
return (i * 8) & 5;
}
unsigned bar (unsigned i)
{
return (i * 6) & 5;
}
/* { dg-final { scan-tree-dump-times "\\\&" 1 "original" } } */
/* { dg-final { scan-tree-dump-times "\\\& 4;" 1 "original" } } */
/* { dg-final { cleanup-tree-dump "original" } } */