[gcc r12-8383] Do not use DW_OP_not for TRUTH_NOT_EXPR in conditional expressions

[Eric Botcazou <ebotcazou@gcc.gnu.org>]

https://gcc.gnu.org/g:ad05a1d7f83aa7ddff9ac6ec5ca65e69042d6907

commit r12-8383-gad05a1d7f83aa7ddff9ac6ec5ca65e69042d6907
Author: Eric Botcazou <ebotcazou@adacore.com>
Date:   Mon May 16 10:44:09 2022 +0200

    Do not use DW_OP_not for TRUTH_NOT_EXPR in conditional expressions
    
    DW_OP_not is a bitwise, not a logical NOT, so it computes the wrong result
    in a DWARF conditional expression.
    
    gcc/
            * dwarf2out.cc (loc_list_from_tree_1) <TRUTH_NOT_EXPR>: Do a logical
            instead of a bitwise negation.
            <COND_EXPR>: Swap the operands if the condition is TRUTH_NOT_EXPR.

Diff:
---
 gcc/dwarf2out.cc | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/gcc/dwarf2out.cc b/gcc/dwarf2out.cc
index 5681b01749a..c333c595026 100644
--- a/gcc/dwarf2out.cc
+++ b/gcc/dwarf2out.cc
@@ -19449,6 +19449,14 @@ loc_list_from_tree_1 (tree loc, int want_address,
       break;
 
     case TRUTH_NOT_EXPR:
+      list_ret = loc_list_from_tree_1 (TREE_OPERAND (loc, 0), 0, context);
+      if (list_ret == 0)
+	return 0;
+
+      add_loc_descr_to_each (list_ret, new_loc_descr (DW_OP_lit0, 0, 0));
+      add_loc_descr_to_each (list_ret, new_loc_descr (DW_OP_eq, 0, 0));
+      break;
+
     case BIT_NOT_EXPR:
       op = DW_OP_not;
       goto do_unop;
@@ -19497,6 +19505,15 @@ loc_list_from_tree_1 (tree loc, int want_address,
 	  list_ret
 	    = loc_list_from_tree_1 (TREE_OPERAND (TREE_OPERAND (loc, 0), 0),
 				    0, context);
+	/* Likewise, swap the operands for a logically negated condition.  */
+	else if (TREE_CODE (TREE_OPERAND (loc, 0)) == TRUTH_NOT_EXPR)
+	  {
+	    lhs = loc_descriptor_from_tree (TREE_OPERAND (loc, 2), 0, context);
+	    rhs = loc_list_from_tree_1 (TREE_OPERAND (loc, 1), 0, context);
+	    list_ret
+	      = loc_list_from_tree_1 (TREE_OPERAND (TREE_OPERAND (loc, 0), 0),
+				      0, context);
+	  }
 	else
 	  list_ret = loc_list_from_tree_1 (TREE_OPERAND (loc, 0), 0, context);
 	if (list_ret == 0 || lhs == 0 || rhs == 0)