POC: automatically move scope array literals to the stack

dlang · Sep 27, 2024 · 62bc416 · 62bc416
1 parent 1d0b93b
commit 62bc416
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diff --git a/compiler/src/dmd/escape.d b/compiler/src/dmd/escape.d
@@ -2056,6 +2056,23 @@ void finishScopeParamInference(FuncDeclaration funcdecl, ref TypeFunction f)
         f.isScopeQual = funcdecl.vthis.isScope();
         f.isScopeInferred = !!(funcdecl.vthis.storage_class & STC.scopeinferred);
     }
+
+    import dmd.foreachvar;
+    void dgVar(VarDeclaration v)
+    {
+        if (v.maybeScope && v._init)
+            if (auto ei = v._init.isExpInitializer())
+                if (auto ce = ei.exp.isConstructExp())
+                    if (auto ale = ce.e2.isArrayLiteralExp())
+                        ale.onstack = true;
+    }
+
+    void dgExp(Expression e)
+    {
+        foreachVar(e, &dgVar);
+    }
+
+    foreachExpAndVar(funcdecl.fbody, &dgExp, &dgVar);
 }
 
 /************************************************

diff --git a/compiler/test/runnable/betterc.d b/compiler/test/runnable/betterc.d
@@ -43,6 +43,7 @@ extern (C) void main()
     testRuntimeLowerings();
     test18457();
     test20737();
+    testScopeInferenceArrayLiteral();
 }
 
 /*******************************************/
@@ -221,3 +222,15 @@ void test22427()
     char[] p;
     auto a = cast(int[])p;
 }
+
+/*******************************************/
+// Test that local variable can be inferred scope, moving
+// array literal from GC to stack, allowing usage in betterC
+
+auto testScopeInferenceArrayLiteral()
+{
+    auto x = [10, 20, 30] ~ [40];
+    x[0] = 50;
+    assert(x[0] + x[1] == 70);
+    return x[0];
+}