Fix #5116 - Skip the sematics checks of compiler-generated functions and template instances in dcompute

gen/semantic-dcompute.cpp

@@ -212,6 +212,11 @@ struct DComputeSemanticAnalyser : public StoppableVisitor {
     }
   }
   void visit(CallExp *e) override {
+    // Indirect calls via function pointers / delegates have no associated
+    // FuncDeclaration, so there is no module to check.
+    if (!e->f)
+      return;
+
     // SynchronizedStatement is lowered to
     //    Critsec __critsec105; // 105 == line number
     //    _d_criticalenter(& __critsec105); <--
@@ -229,9 +234,15 @@ struct DComputeSemanticAnalyser : public StoppableVisitor {
       stop = true;
       return;
     }
-      
+
     Module *m = e->f->getModule();
-    if ((m == nullptr || (hasComputeAttr(m) == DComputeCompileFor::hostOnly)) &&
+    // Template-instantiated functions are cross-module by nature: the template
+    // declaration and the instantiated function live in different modules.
+    // getModule() returns the *declaration* module, which says nothing about
+    // whether the generated code can run on GPU. Skip the module check for them.
+    const bool isTemplateFunc = e->f->isInstantiated() != nullptr;
+    if (!isTemplateFunc &&
+        (m == nullptr || (hasComputeAttr(m) == DComputeCompileFor::hostOnly)) &&
         !isNonComputeCallExpVaild(e)) {
       error(e->loc, "can only call functions from other `@compute` modules in "
                     "`@compute` code");

tests/compilable/issue5116.d

@@ -0,0 +1,26 @@
+// Without this patch, template instantiations from non-@compute modules (e.g.
+// __equals from core.internal.array.equality) were walked, producing spurious errors.
+// And indirect calls via function pointers inside those bodies additionally caused a
+// null-pointer dereference crash.
+
+// REQUIRES: target_NVPTX
+// RUN: %ldc -mdcompute-targets=cuda-350 %s
+
+@compute(CompileFor.deviceOnly) module tests.compilable.issue5116;
+import ldc.dcompute;
+
+private enum N = 16u;
+
+struct S {
+    float[N] data;
+}
+
+@kernel void testEqualExp() {
+    float[N] a, b;
+    bool c = (a == b);
+}
+
+@kernel void testExplicitEquals() {
+    float[N] a, b;
+    bool c = __equals(a, b);
+}