From c77230856eac2d28eb7bf10985846885c3c8727b Mon Sep 17 00:00:00 2001
From: Iain Buclaw <ibuclaw@gdcproject.org>
Date: Sat, 3 Jul 2021 00:13:29 +0200
Subject: [PATCH] d: RHS value lost when a target_expr modifies LHS in a
 cond_expr

To prevent the RHS of an assignment modifying the LHS before the
assignment proper, a target_expr is forced so that function calls that
return with slot optimization modify the temporary instead.  This did
not work for conditional expressions however, to give one example.  So
now the RHS is always forced to a temporary.

	PR d/101282

gcc/d/ChangeLog:

	* d-codegen.cc (build_assign): Force target_expr on RHS for non-POD
	assignment expressions.

gcc/testsuite/ChangeLog:

	* gdc.dg/torture/pr101282.d: New test.
---
 gcc/d/d-codegen.cc                      |  7 +++++++
 gcc/testsuite/gdc.dg/torture/pr101282.d | 23 +++++++++++++++++++++++
 2 files changed, 30 insertions(+)
 create mode 100644 gcc/testsuite/gdc.dg/torture/pr101282.d

diff --git a/gcc/d/d-codegen.cc b/gcc/d/d-codegen.cc
index 9a94473..ce7c17b 100644
--- a/gcc/d/d-codegen.cc
+++ b/gcc/d/d-codegen.cc
@@ -1344,6 +1344,13 @@ build_assign (tree_code code, tree lhs, tree rhs)
       d_mark_addressable (lhs);
       CALL_EXPR_RETURN_SLOT_OPT (rhs) = true;
     }
+  /* If modifying an LHS whose type is marked TREE_ADDRESSABLE.  */
+  else if (code == MODIFY_EXPR && TREE_ADDRESSABLE (TREE_TYPE (lhs))
+	   && TREE_SIDE_EFFECTS (rhs) && TREE_CODE (rhs) != TARGET_EXPR)
+    {
+      /* LHS may be referenced by the RHS expression, so force a temporary.  */
+      rhs = force_target_expr (rhs);
+    }
 
   /* The LHS assignment replaces the temporary in TARGET_EXPR_SLOT.  */
   if (TREE_CODE (rhs) == TARGET_EXPR)
diff --git a/gcc/testsuite/gdc.dg/torture/pr101282.d b/gcc/testsuite/gdc.dg/torture/pr101282.d
new file mode 100644
index 0000000..b75d5fc
--- /dev/null
+++ b/gcc/testsuite/gdc.dg/torture/pr101282.d
@@ -0,0 +1,23 @@
+// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101282
+// { dg-do run }
+
+void main()
+{
+    struct S101282
+    {
+        int impl;
+        S101282 opUnary(string op : "-")()
+        {
+            return S101282(-impl);
+        }
+        int opCmp(int i)
+        {
+            return (impl < i) ? -1 : (impl > i) ? 1 : 0;
+        }
+    }
+    auto a = S101282(120);
+    a = -a;
+    assert(a.impl == -120);
+    a = a >= 0 ? a : -a;
+    assert(a.impl == 120);
+}
-- 
2.7.4