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;