This makes sure we fold conversion chains where the outermost
conversion is a sign-change only and that we associate expressions
in more cases when two variables appear but they have equal
value.
Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
Richard.
2012-03-13 Richard Guenther <rguent...@suse.de>
PR middle-end/52578
* fold-const.c (fold_unary_loc): Fold (T1)(T2)x to (T1)x if
the outermost conversion is a sign-change only.
(fold_binary_loc): Disregard widening and sign-changing
conversions when we determine if two variables are equal
for reassociation.
* tree-ssa-forwprop.c (combine_conversions): Fold (T1)(T2)x to
(T1)x if the outermost conversion is a sign-change only.
* gcc.dg/pr52578.c: New testcase.
Index: gcc/fold-const.c
===================================================================
--- gcc/fold-const.c (revision 185322)
+++ gcc/fold-const.c (working copy)
@@ -7843,10 +7843,13 @@ fold_unary_loc (location_t loc, enum tre
return fold_build1_loc (loc, code, type, TREE_OPERAND (op0, 0));
/* If we have a sign-extension of a zero-extended value, we can
- replace that by a single zero-extension. */
+ replace that by a single zero-extension. Likewise if the
+ final conversion does not change precision we can drop the
+ intermediate conversion. */
if (inside_int && inter_int && final_int
- && inside_prec < inter_prec && inter_prec < final_prec
- && inside_unsignedp && !inter_unsignedp)
+ && ((inside_prec < inter_prec && inter_prec < final_prec
+ && inside_unsignedp && !inter_unsignedp)
+ || final_prec == inter_prec))
return fold_build1_loc (loc, code, type, TREE_OPERAND (op0, 0));
/* Two conversions in a row are not needed unless:
@@ -10335,10 +10341,21 @@ fold_binary_loc (location_t loc,
if (TREE_CODE (tmp0) == NEGATE_EXPR)
tmp0 = TREE_OPERAND (tmp0, 0);
+ if (CONVERT_EXPR_P (tmp0)
+ && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (tmp0, 0)))
+ && (TYPE_PRECISION (TREE_TYPE (TREE_OPERAND (tmp0, 0)))
+ <= TYPE_PRECISION (type)))
+ tmp0 = TREE_OPERAND (tmp0, 0);
if (TREE_CODE (tmp1) == NEGATE_EXPR)
tmp1 = TREE_OPERAND (tmp1, 0);
+ if (CONVERT_EXPR_P (tmp1)
+ && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (tmp1, 0)))
+ && (TYPE_PRECISION (TREE_TYPE (TREE_OPERAND (tmp1, 0)))
+ <= TYPE_PRECISION (type)))
+ tmp1 = TREE_OPERAND (tmp1, 0);
/* The only case we can still associate with two variables
- is if they are the same, modulo negation. */
+ is if they are the same, modulo negation and bit-pattern
+ preserving conversions. */
if (!operand_equal_p (tmp0, tmp1, 0))
ok = false;
}
Index: gcc/tree-ssa-forwprop.c
===================================================================
--- gcc/tree-ssa-forwprop.c (revision 185322)
+++ gcc/tree-ssa-forwprop.c (working copy)
@@ -2285,10 +2285,13 @@ combine_conversions (gimple_stmt_iterato
}
/* If we have a sign-extension of a zero-extended value, we can
- replace that by a single zero-extension. */
+ replace that by a single zero-extension. Likewise if the
+ final conversion does not change precision we can drop the
+ intermediate conversion. */
if (inside_int && inter_int && final_int
- && inside_prec < inter_prec && inter_prec < final_prec
- && inside_unsignedp && !inter_unsignedp)
+ && ((inside_prec < inter_prec && inter_prec < final_prec
+ && inside_unsignedp && !inter_unsignedp)
+ || final_prec == inter_prec))
{
gimple_assign_set_rhs1 (stmt, defop0);
update_stmt (stmt);
Index: gcc/testsuite/gcc.dg/pr52578.c
===================================================================
--- gcc/testsuite/gcc.dg/pr52578.c (revision 0)
+++ gcc/testsuite/gcc.dg/pr52578.c (revision 0)
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-fdump-tree-original" } */
+
+long bar (long i)
+{
+ return (long)((unsigned long)i + 2) - (long)i;
+}
+long foo (int i)
+{
+ return (long)((unsigned long)i + 2) - (long)i;
+}
+
+/* { dg-final { scan-tree-dump-times "return 2;" 2 "original" } } */
+/* { dg-final { cleanup-tree-dump "original" } } */
