Hi,
the comment of the function reads:
/* Given a tree comparison code, return the code that is the logical inverse
of the given code. It is not safe to do this for floating-point
comparisons, except for NE_EXPR and EQ_EXPR, so we receive a machine mode
as well: if reversing the comparison is unsafe, return ERROR_MARK. */
but the function starts with:
if (honor_nans && flag_trapping_math)
return ERROR_MARK;
so, for example, it refuses to fold !(x == y) to x != y for FP, which is valid.
Fixed by letting EQ_EXPR and NE_EXPR go through. This makes tree-opt/44683
regress though, but it's clear that the original fix only papered over the
problem, as you can't infer a simple equivalence from a condition when you can
have signed zeros around; so the patch also includes the proper fix.
Tested on x86_64-suse-linux, OK for mainline?
2011-10-23 Eric Botcazou <ebotca...@adacore.com>
* fold-const.c (invert_tree_comparison): Always invert EQ_EXPR/NE_EXPR.
PR tree-optimization/44683
* tree-ssa-dom.c (record_edge_info): Record simple equivalences only if
we can be sure that there are no signed zeros involved.
--
Eric Botcazou
Index: fold-const.c
===================================================================
--- fold-const.c (revision 180235)
+++ fold-const.c (working copy)
@@ -2100,15 +2100,14 @@ pedantic_non_lvalue_loc (location_t loc,
return protected_set_expr_location_unshare (x, loc);
}
-/* Given a tree comparison code, return the code that is the logical inverse
- of the given code. It is not safe to do this for floating-point
- comparisons, except for NE_EXPR and EQ_EXPR, so we receive a machine mode
- as well: if reversing the comparison is unsafe, return ERROR_MARK. */
+/* Given a tree comparison code, return the code that is the logical inverse.
+ It is generally not safe to do this for floating-point comparisons, except
+ for EQ_EXPR and NE_EXPR, so we return ERROR_MARK in this case. */
enum tree_code
invert_tree_comparison (enum tree_code code, bool honor_nans)
{
- if (honor_nans && flag_trapping_math)
+ if (honor_nans && flag_trapping_math && code != EQ_EXPR && code != NE_EXPR)
return ERROR_MARK;
switch (code)
Index: tree-ssa-dom.c
===================================================================
--- tree-ssa-dom.c (revision 180235)
+++ tree-ssa-dom.c (working copy)
@@ -1610,12 +1610,15 @@ record_edge_info (basic_block bb)
{
tree cond = build2 (code, boolean_type_node, op0, op1);
tree inverted = invert_truthvalue_loc (loc, cond);
+ enum machine_mode mode = TYPE_MODE (TREE_TYPE (op0));
+ bool can_infer_simple_equiv
+ = !(HONOR_SIGNED_ZEROS (mode) && real_zerop (op0));
struct edge_info *edge_info;
edge_info = allocate_edge_info (true_edge);
record_conditions (edge_info, cond, inverted);
- if (code == EQ_EXPR)
+ if (can_infer_simple_equiv && code == EQ_EXPR)
{
edge_info->lhs = op1;
edge_info->rhs = op0;
@@ -1624,7 +1627,7 @@ record_edge_info (basic_block bb)
edge_info = allocate_edge_info (false_edge);
record_conditions (edge_info, inverted, cond);
- if (TREE_CODE (inverted) == EQ_EXPR)
+ if (can_infer_simple_equiv && TREE_CODE (inverted) == EQ_EXPR)
{
edge_info->lhs = op1;
edge_info->rhs = op0;
@@ -1632,17 +1635,21 @@ record_edge_info (basic_block bb)
}
else if (TREE_CODE (op0) == SSA_NAME
- && (is_gimple_min_invariant (op1)
- || TREE_CODE (op1) == SSA_NAME))
+ && (TREE_CODE (op1) == SSA_NAME
+ || is_gimple_min_invariant (op1)))
{
tree cond = build2 (code, boolean_type_node, op0, op1);
tree inverted = invert_truthvalue_loc (loc, cond);
+ enum machine_mode mode = TYPE_MODE (TREE_TYPE (op1));
+ bool can_infer_simple_equiv
+ = !(HONOR_SIGNED_ZEROS (mode)
+ && (TREE_CODE (op1) == SSA_NAME || real_zerop (op1)));
struct edge_info *edge_info;
edge_info = allocate_edge_info (true_edge);
record_conditions (edge_info, cond, inverted);
- if (code == EQ_EXPR)
+ if (can_infer_simple_equiv && code == EQ_EXPR)
{
edge_info->lhs = op0;
edge_info->rhs = op1;
@@ -1651,7 +1658,7 @@ record_edge_info (basic_block bb)
edge_info = allocate_edge_info (false_edge);
record_conditions (edge_info, inverted, cond);
- if (TREE_CODE (inverted) == EQ_EXPR)
+ if (can_infer_simple_equiv && TREE_CODE (inverted) == EQ_EXPR)
{
edge_info->lhs = op0;
edge_info->rhs = op1;
