Merge pull request #6847 from WalterBright/fix17457

fix Issue 17457 - Named Return Value Optimization (NRVO) not done wit… merged-on-behalf-of: Andrei Alexandrescu <andralex@users.noreply.github.com>
dlang · Jun 10, 2017 · 10e086a · 10e086a
2 parents 51b5a07 + 2fd9691
commit 10e086a
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Showing 2 changed files with 54 additions and 1 deletion.
diff --git a/src/ddmd/s2ir.d b/src/ddmd/s2ir.d
@@ -773,6 +773,7 @@ extern (C++) class S2irVisitor : Visitor
 
     override void visit(ReturnStatement s)
     {
+        //printf("s2ir.ReturnStatement: %s\n", s.toChars());
         Blockx *blx = irs.blx;
         BC bc;
 
@@ -790,6 +791,7 @@ extern (C++) class S2irVisitor : Visitor
             if (retmethod == RETstack)
             {
                 elem *es;
+                bool writetohp;
 
                 /* If returning struct literal, write result
                  * directly into return value
@@ -798,11 +800,34 @@ extern (C++) class S2irVisitor : Visitor
                 {
                     StructLiteralExp sle = cast(StructLiteralExp)s.exp;
                     sle.sym = irs.shidden;
+                    writetohp = true;
+                }
+                /* Detect:
+                 *    structliteral.ctor(args)
+                 * and construct directly into *shidden
+                 */
+                else if (s.exp.op == TOKcall)
+                {
+                    auto ce = cast(CallExp)s.exp;
+                    if (ce.e1.op == TOKdotvar)
+                    {
+                        auto dve = cast(DotVarExp)ce.e1;
+                        auto fd = dve.var.isFuncDeclaration();
+                        if (fd && fd.isCtorDeclaration())
+                        {
+                            if (dve.e1.op == TOKstructliteral)
+                            {
+                                auto sle = cast(StructLiteralExp)dve.e1;
+                                sle.sym = irs.shidden;
+                                writetohp = true;
+                            }
+                        }
+                    }
                 }
                 e = toElemDtor(s.exp, irs);
                 assert(e);
 
-                if (s.exp.op == TOKstructliteral ||
+                if (writetohp ||
                     (func.nrvo_can && func.nrvo_var))
                 {
                     // Return value via hidden pointer passed as parameter

diff --git a/test/runnable/sdtor.d b/test/runnable/sdtor.d
@@ -2815,6 +2815,33 @@ void test9985()
     static assert(is(typeof(retX) == F2));
 }
 
+/**********************************/
+
+// https://issues.dlang.org/show_bug.cgi?id=17457
+
+void delegate() dg17457;
+
+struct S17457 {
+    ulong[10] data;
+
+    this(int seconds) {
+        dg17457 = &mfunc;
+    }
+    void mfunc() {}
+}
+
+auto foo17457() {
+    pragma(inline, false);
+    return S17457(18);
+}
+
+void test17457()
+{
+    auto x = foo17457();
+    //printf("%p vs %p\n", &x, dg17457.ptr);
+    assert(&x == dg17457.ptr);
+}
+
 /**********************************/
 // 9994
 
@@ -4546,6 +4573,7 @@ int main()
     test9899();
     test9907();
     test9985();
+    test17457();
     test9994();
     test10094();
     test10244();