Hi,
When casting from bool, the result is either 0 or 1, any other value
violates @safe code, so enforce that it is never invalid.
This patch does that by lowering rvalue reads into `(bool & 1)'.
Bootstrapped and regression tested on x86_64-linux-gnu/-mx32/-m32,
committed to mainline, and backported to the gcc-11, gcc-10 and gcc-9
release branches.
Regards,
Iain
---
gcc/d/ChangeLog:
PR d/96435
* d-convert.cc (convert_for_rvalue): New function.
* d-tree.h (convert_for_rvalue): Declare.
* expr.cc (ExprVisitor::visit (CastExp *)): Use convert_for_rvalue.
(build_return_dtor): Likewise.
gcc/testsuite/ChangeLog:
PR d/96435
* gdc.dg/torture/pr96435.d: New test.
---
gcc/d/d-convert.cc | 36 ++++++++++++++++++++++++++
gcc/d/d-tree.h | 1 +
gcc/d/expr.cc | 13 ++++++----
gcc/testsuite/gdc.dg/torture/pr96435.d | 21 +++++++++++++++
4 files changed, 66 insertions(+), 5 deletions(-)
create mode 100644 gcc/testsuite/gdc.dg/torture/pr96435.d
diff --git a/gcc/d/d-convert.cc b/gcc/d/d-convert.cc
index 237c084acf5..d43485dca77 100644
--- a/gcc/d/d-convert.cc
+++ b/gcc/d/d-convert.cc
@@ -602,6 +602,42 @@ convert_expr (tree exp, Type *etype, Type *totype)
return result ? result : convert (build_ctype (totype), exp);
}
+/* Return a TREE represenwation of EXPR, whose type has been converted from
+ * ETYPE to TOTYPE, and is being used in an rvalue context. */
+
+tree
+convert_for_rvalue (tree expr, Type *etype, Type *totype)
+{
+ tree result = NULL_TREE;
+
+ Type *ebtype = etype->toBasetype ();
+ Type *tbtype = totype->toBasetype ();
+
+ switch (ebtype->ty)
+ {
+ case Tbool:
+ /* If casting from bool, the result is either 0 or 1, any other value
+ violates @safe code, so enforce that it is never invalid. */
+ if (CONSTANT_CLASS_P (expr))
+ result = d_truthvalue_conversion (expr);
+ else
+ {
+ /* Reinterpret the boolean as an integer and test the first bit.
+ The generated code should end up being equivalent to:
+ *cast(ubyte *)&expr & 1; */
+ machine_mode bool_mode = TYPE_MODE (TREE_TYPE (expr));
+ tree mtype = lang_hooks.types.type_for_mode (bool_mode, 1);
+ result = fold_build2 (BIT_AND_EXPR, mtype,
+ build_vconvert (mtype, expr),
+ build_one_cst (mtype));
+ }
+
+ result = convert (build_ctype (tbtype), result);
+ break;
+ }
+
+ return result ? result : convert_expr (expr, etype, totype);
+}
/* Apply semantics of assignment to a value of type TOTYPE to EXPR
(e.g., pointer = array -> pointer = &array[0])
diff --git a/gcc/d/d-tree.h b/gcc/d/d-tree.h
index b03d60a5c0e..f210b8b1a6e 100644
--- a/gcc/d/d-tree.h
+++ b/gcc/d/d-tree.h
@@ -598,6 +598,7 @@ extern bool decl_with_nonnull_addr_p (const_tree);
extern tree d_truthvalue_conversion (tree);
extern tree d_convert (tree, tree);
extern tree convert_expr (tree, Type *, Type *);
+extern tree convert_for_rvalue (tree, Type *, Type *);
extern tree convert_for_assignment (tree, Type *, Type *);
extern tree convert_for_argument (tree, Parameter *);
extern tree convert_for_condition (tree, Type *);
diff --git a/gcc/d/expr.cc b/gcc/d/expr.cc
index b78778eb8ef..99ca958c7c4 100644
--- a/gcc/d/expr.cc
+++ b/gcc/d/expr.cc
@@ -1491,7 +1491,7 @@ public:
if (tbtype->ty == Tvoid)
this->result_ = build_nop (build_ctype (tbtype), result);
else
- this->result_ = convert_expr (result, ebtype, tbtype);
+ this->result_ = convert_for_rvalue (result, ebtype, tbtype);
}
/* Build a delete expression. */
@@ -3169,11 +3169,14 @@ build_return_dtor (Expression *e, Type *type,
TypeFunction *tf)
tree result = build_expr (e);
/* Convert for initializing the DECL_RESULT. */
- result = convert_expr (result, e->type, type);
-
- /* If we are returning a reference, take the address. */
if (tf->isref)
- result = build_address (result);
+ {
+ /* If we are returning a reference, take the address. */
+ result = convert_expr (result, e->type, type);
+ result = build_address (result);
+ }
+ else
+ result = convert_for_rvalue (result, e->type, type);
/* The decl to store the return expression. */
tree decl = DECL_RESULT (cfun->decl);
diff --git a/gcc/testsuite/gdc.dg/torture/pr96435.d
b/gcc/testsuite/gdc.dg/torture/pr96435.d
new file mode 100644
index 00000000000..c6d8785ec5b
--- /dev/null
+++ b/gcc/testsuite/gdc.dg/torture/pr96435.d
@@ -0,0 +1,21 @@
+// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96435
+// { dg-do run }
+
+@safe bool test96435()
+{
+ int[2] array = [16, 678];
+ union U { int i; bool b; }
+ U u;
+ u.i = 0xDEADBEEF;
+ assert(array[u.b] == 678);
+ return u.b;
+}
+
+@safe void main()
+{
+ auto b = test96435();
+ if (b)
+ assert(true);
+ if (!b)
+ assert(false);
+}
--
2.30.2
