[gcc r10-9043] d: Fix LHS of array concatentation evaluated before the RHS.

[Iain Buclaw]

https://gcc.gnu.org/g:bbb887834d78cf6a444bf9cecc29d14b4dfb9cf8

commit r10-9043-gbbb887834d78cf6a444bf9cecc29d14b4dfb9cf8
Author: Iain Buclaw <ibuclaw@gdcproject.org>
Date:   Tue Nov 17 13:11:33 2020 +0100

    d: Fix LHS of array concatentation evaluated before the RHS.
    
    In an array append expression:
    
        array ~= fun(array);
    
    The array in the left hand side of the expression was extended before
    evaluating the result of the right hand side, which resulted in the
    newly uninitialized array index being used before set.
    
    This fixes that so that the result of the right hand side is always
    saved in a reusable temporary before assigning to the destination.
    
    gcc/d/ChangeLog:
    
            PR d/97843
            * d-codegen.cc (build_assign): Evaluate TARGET_EXPR before use in
            the right hand side of an assignment.
            * expr.cc (ExprVisitor::visit (CatAssignExp *)): Force a TARGET_EXPR
            on the element to append if it is a CALL_EXPR.
    
    gcc/testsuite/ChangeLog:
    
            PR d/97843
            * gdc.dg/pr97843.d: New test.
    
    (cherry picked from commit 798bdfa0ebcf2bd012ffce75a594f783a8cb2dd0)

Diff:
---
 gcc/d/d-codegen.cc             |  5 ++++-
 gcc/d/expr.cc                  |  3 +++
 gcc/testsuite/gdc.dg/pr97843.d | 37 +++++++++++++++++++++++++++++++++++++
 3 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/gcc/d/d-codegen.cc b/gcc/d/d-codegen.cc
index f57caf226d4..8042f03f369 100644
--- a/gcc/d/d-codegen.cc
+++ b/gcc/d/d-codegen.cc
@@ -1290,7 +1290,10 @@ build_assign (tree_code code, tree lhs, tree rhs)
 	 since that would cause the LHS to be constructed twice.
 	 So we force the TARGET_EXPR to be expanded without a target.  */
       if (code != INIT_EXPR)
-	rhs = compound_expr (rhs, TARGET_EXPR_SLOT (rhs));
+	{
+	  init = compound_expr (init, rhs);
+	  rhs = TARGET_EXPR_SLOT (rhs);
+	}
       else
 	{
 	  d_mark_addressable (lhs);
diff --git a/gcc/d/expr.cc b/gcc/d/expr.cc
index 9191d3a9510..acc54f39de3 100644
--- a/gcc/d/expr.cc
+++ b/gcc/d/expr.cc
@@ -884,6 +884,9 @@ public:
 	    tree t2 = build_expr (e->e2);
 	    tree expr = stabilize_expr (&t2);
 
+	    if (TREE_CODE (t2) == CALL_EXPR)
+	      t2 = force_target_expr (t2);
+
 	    result = modify_expr (build_deref (ptrexp), t2);
 
 	    this->result_ = compound_expr (expr, result);
diff --git a/gcc/testsuite/gdc.dg/pr97843.d b/gcc/testsuite/gdc.dg/pr97843.d
new file mode 100644
index 00000000000..29a9d04fa07
--- /dev/null
+++ b/gcc/testsuite/gdc.dg/pr97843.d
@@ -0,0 +1,37 @@
+// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97843
+// { dg-additional-options "-fmain -funittest" }
+// { dg-do run { target hw } }
+// { dg-skip-if "needs gcc/config.d" { ! d_runtime } }
+
+struct Sdtor
+{
+    int value;
+    ~this() { }
+}
+
+Sdtor sum(Sdtor[] sdtors)
+{
+    int result;
+    foreach (s; sdtors)
+        result += s.value;
+    return Sdtor(result);
+}
+
+uint sum(uint[] ints)
+{
+    uint result;
+    foreach(i; ints)
+        result += i;
+    return result;
+}
+
+unittest
+{
+    Sdtor[] sdtors = [Sdtor(0), Sdtor(1)];
+    sdtors ~= sum(sdtors);
+    assert(sdtors == [Sdtor(0), Sdtor(1), Sdtor(1)]);
+
+    uint[] ints = [0, 1];
+    ints ~= ints.sum;
+    assert(ints == [0, 1, 1]);
+}