This adds a pattern matching x != ~x on GIMPLE and allows CCP to
properly optimize the added testcase. gimple_simplify gets confused
by the existing ~x == 1 -> x == 0 pattern which
gimple_fold_stmt_to_constant_1 cannot reduce to a single value.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
Richard.
2015-08-04 Richard Biener <rguent...@suse.de>
* gimple-fold.c (gimple_fold_stmt_to_constant_1): Canonicalize
bool compares on RHS.
* match.pd: Add X ==/!= !X is false/true pattern.
* gcc.dg/tree-ssa/ssa-ccp-38.c: New testcase.
Index: gcc/gimple-fold.c
===================================================================
--- gcc/gimple-fold.c (revision 226559)
+++ gcc/gimple-fold.c (working copy)
@@ -5012,10 +5012,8 @@ gimple_fold_stmt_to_constant_1 (gimple s
further propagation. */
if (subcode == POINTER_PLUS_EXPR)
{
- /* Handle binary operators that can appear in GIMPLE form. */
tree op0 = (*valueize) (gimple_assign_rhs1 (stmt));
tree op1 = (*valueize) (gimple_assign_rhs2 (stmt));
-
if (TREE_CODE (op0) == ADDR_EXPR
&& TREE_CODE (op1) == INTEGER_CST)
{
@@ -5027,6 +5025,38 @@ gimple_fold_stmt_to_constant_1 (gimple s
unshare_expr (op0), off));
}
}
+ /* Canonicalize bool != 0 and bool == 0 appearing after
+ valueization. While gimple_simplify handles this
+ it can get confused by the ~X == 1 -> X == 0 transform
+ which we cant reduce to a SSA name or a constant
+ (and we have no way to tell gimple_simplify to not
+ consider those transforms in the first place). */
+ else if (subcode == EQ_EXPR
+ || subcode == NE_EXPR)
+ {
+ tree lhs = gimple_assign_lhs (stmt);
+ tree op0 = gimple_assign_rhs1 (stmt);
+ if (useless_type_conversion_p (TREE_TYPE (lhs),
+ TREE_TYPE (op0)))
+ {
+ tree op1 = (*valueize) (gimple_assign_rhs2 (stmt));
+ op0 = (*valueize) (op0);
+ if (subcode == NE_EXPR)
+ {
+ if (integer_zerop (op1))
+ return op0;
+ else if (integer_zerop (op0))
+ return op1;
+ }
+ else
+ {
+ if (integer_onep (op1))
+ return op0;
+ else if (integer_onep (op0))
+ return op1;
+ }
+ }
+ }
return NULL_TREE;
case GIMPLE_TERNARY_RHS:
Index: gcc/match.pd
===================================================================
--- gcc/match.pd (revision 226559)
+++ gcc/match.pd (working copy)
@@ -618,6 +618,11 @@ (define_operator_list CBRT BUILT_IN_CBRT
(simplify
(op:c truth_valued_p@0 (logical_inverted_value @0))
{ constant_boolean_node (true, type); }))
+/* X ==/!= !X is false/true. */
+(for op (eq ne)
+ (simplify
+ (op:c truth_valued_p@0 (logical_inverted_value @0))
+ { constant_boolean_node (op == NE_EXPR ? true : false, type); }))
/* If arg1 and arg2 are booleans (or any single bit type)
then try to simplify:
Index: gcc/testsuite/gcc.dg/tree-ssa/ssa-ccp-38.c
===================================================================
--- gcc/testsuite/gcc.dg/tree-ssa/ssa-ccp-38.c (revision 0)
+++ gcc/testsuite/gcc.dg/tree-ssa/ssa-ccp-38.c (working copy)
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-ccp1" } */
+
+int foo (_Bool x)
+{
+ _Bool t = 1;
+ _Bool xx = !x;
+ _Bool y = xx == t;
+ _Bool z = y == x;
+ return z ? 1 : 0;
+}
+
+/* { dg-final { scan-tree-dump "return 0;" "ccp1" } } */
