Hello,
this patch adds to fold_binary_loc some missing optimization for binary
and operations on truth-not expressions.
Added cases are:
(!X & X) is always zero.
(X & !X) is always zero.
(X == 0) & X is always zero.
X & (X == 0) is always zero.
!X & 1 is X == 0
ChangeLog
2011-06-20 Kai Tietz <kti...@redhat.com>
* fold-const.c (fold_binary_loc): Add missing
folding for truth-not operations in combination
with binary and.
ChangeLog
2011-06-20 Kai Tietz <kti...@redhat.com>
* gcc.dg/binop-notand1.c: New test.
* gcc.dg/binop-notand2.c: New test.
* gcc.dg/binop-notand3.c: New test.
* gcc.dg/binop-notand4.c: New test.
* gcc.dg/binop-notand5.c: New test.
* gcc.dg/binop-notand6.c: New test.
Boostrapped and tested for x86_64-pc-linux-gnu. Ok for apply?
Regards,
Kai
Index: gcc/gcc/fold-const.c
===================================================================
--- gcc.orig/gcc/fold-const.c 2011-06-20 10:45:33.000000000 +0200
+++ gcc/gcc/fold-const.c 2011-06-20 12:03:57.974484000 +0200
@@ -10866,13 +10866,19 @@ fold_binary_loc (location_t loc,
if (operand_equal_p (arg0, arg1, 0))
return non_lvalue_loc (loc, fold_convert_loc (loc, type, arg0));
- /* ~X & X is always zero. */
- if (TREE_CODE (arg0) == BIT_NOT_EXPR
+ /* ~X & X, (X == 0) & X, and !X & X are always zero. */
+ if ((TREE_CODE (arg0) == BIT_NOT_EXPR
+ || TREE_CODE (arg0) == TRUTH_NOT_EXPR
+ || (TREE_CODE (arg0) == EQ_EXPR
+ && integer_zerop (TREE_OPERAND (arg0, 1))))
&& operand_equal_p (TREE_OPERAND (arg0, 0), arg1, 0))
return omit_one_operand_loc (loc, type, integer_zero_node, arg1);
- /* X & ~X is always zero. */
- if (TREE_CODE (arg1) == BIT_NOT_EXPR
+ /* X & ~X , X & (X == 0), and X & !X are always zero. */
+ if ((TREE_CODE (arg1) == BIT_NOT_EXPR
+ || TREE_CODE (arg1) == TRUTH_NOT_EXPR
+ || (TREE_CODE (arg1) == EQ_EXPR
+ && integer_zerop (TREE_OPERAND (arg1, 1))))
&& operand_equal_p (arg0, TREE_OPERAND (arg1, 0), 0))
return omit_one_operand_loc (loc, type, integer_zero_node, arg0);
@@ -10933,6 +10939,14 @@ fold_binary_loc (location_t loc,
build_int_cst (TREE_TYPE (tem), 1)),
build_int_cst (TREE_TYPE (tem), 0));
}
+ /* Fold !X & 1 as X == 0. */
+ if (TREE_CODE (arg0) == TRUTH_NOT_EXPR
+ && integer_onep (arg1))
+ {
+ tem = TREE_OPERAND (arg0, 0);
+ return fold_build2_loc (loc, EQ_EXPR, type, tem,
+ build_int_cst (TREE_TYPE (tem), 0));
+ }
/* Fold (X ^ Y) & Y as ~X & Y. */
if (TREE_CODE (arg0) == BIT_XOR_EXPR
Index: gcc/gcc/testsuite/gcc.dg/binop-notand1.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ gcc/gcc/testsuite/gcc.dg/binop-notand1.c 2011-06-20 11:02:49.718674700
+0200
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int
+foo (int a, int b)
+{
+ return (a & !a) | (b & !b);
+}
+
+/* { dg-final { scan-tree-dump-times "return 0" 1 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Index: gcc/gcc/testsuite/gcc.dg/binop-notand2.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ gcc/gcc/testsuite/gcc.dg/binop-notand2.c 2011-06-20 11:31:36.415937400
+0200
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int
+foo (int a)
+{
+ return (!a & 1) != (a == 0);
+}
+
+/* { dg-final { scan-tree-dump-times "return 0" 1 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Index: gcc/gcc/testsuite/gcc.dg/binop-notand3.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ gcc/gcc/testsuite/gcc.dg/binop-notand3.c 2011-06-20 11:33:55.974159000
+0200
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int
+foo (int a)
+{
+ return (!a & 1) != ((a == 0) & 1);
+}
+
+/* { dg-final { scan-tree-dump-times "return 0" 1 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Index: gcc/gcc/testsuite/gcc.dg/binop-notand4.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ gcc/gcc/testsuite/gcc.dg/binop-notand4.c 2011-06-20 11:36:39.907475900
+0200
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int
+foo (int a, int b)
+{
+ return (!a & a) | (b & !b);
+}
+
+/* { dg-final { scan-tree-dump-times "return 0" 1 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Index: gcc/gcc/testsuite/gcc.dg/binop-notand5.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ gcc/gcc/testsuite/gcc.dg/binop-notand5.c 2011-06-20 12:05:58.436280700
+0200
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int
+foo (int a, int b)
+{
+ return (a & (a == 0)) | (b & !b);
+}
+
+/* { dg-final { scan-tree-dump-times "return 0" 1 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Index: gcc/gcc/testsuite/gcc.dg/binop-notand6.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ gcc/gcc/testsuite/gcc.dg/binop-notand6.c 2011-06-20 12:05:46.351746200
+0200
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int
+foo (int a, int b)
+{
+ return (a & !a) | (b & (b == 0));
+}
+
+/* { dg-final { scan-tree-dump-times "return 0" 1 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
