From ad9fc55abd20a1501ab649693818a93b1538f375 Mon Sep 17 00:00:00 2001
From: Richard Guenther <rguenther@suse.de>
Date: Tue, 8 May 2012 12:50:18 +0000
Subject: [PATCH] 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
---
gcc/ChangeLog | 5 +++++
gcc/fold-const.c | 24 ++++++++++++++++++++++++
gcc/testsuite/ChangeLog | 4 ++++
gcc/testsuite/gcc.dg/fold-bitand-4.c | 16 ++++++++++++++++
4 files changed, 49 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/fold-bitand-4.c
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index a140b83847b6..b71e988e1003 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -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.
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index f8b31b7d1134..5bb75d490d98 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -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,
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index f9ef02a8278f..ca4bcf89c6e4 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -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
diff --git a/gcc/testsuite/gcc.dg/fold-bitand-4.c b/gcc/testsuite/gcc.dg/fold-bitand-4.c
new file mode 100644
index 000000000000..dba83615dfe7
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fold-bitand-4.c
@@ -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" } } */
--
GitLab