SILGen: Avoid attempting to profile any ClangImporter synthesized function.

ClangImporter synthesized declarations inherently do not have user written
code. Unfortunately, despite that they are not always marked implicit as they
should be. This was causing a crash when attempting to generate profile
coverage maps for synthesized constructors for imported structs.

I tried marking the constructors implicit, but that had too many knock-on
effects in tests. This more targeted fix unblocks compatibility suite testing
without trying to grapple with the implications of that more fundamental fix.

Resolves rdar://139486938.

Author: tshortli

lib/SIL/IR/SILDeclRef.cpp

@@ -316,6 +316,14 @@ bool SILDeclRef::hasUserWrittenCode() const {
       // Never has user-written code, is just a forwarding initializer.
       return false;
     default:
+      if (auto decl = getDecl()) {
+        // Declarations synthesized by ClangImporter by definition don't have
+        // user written code, but despite that they aren't always marked
+        // implicit.
+        auto moduleContext = decl->getDeclContext()->getModuleScopeContext();
+        if (isa<ClangModuleUnit>(moduleContext))
+          return false;
+      }
       // TODO: This checking is currently conservative, we ought to
       // exhaustively handle all the cases here, and use emitOrDelayFunction
       // in more cases to take advantage of it.

test/Profiler/Inputs/issue-57483/cmodule.h renamed to test/Profiler/Inputs/CModule/cmodule.h

@@ -1,14 +1,17 @@
-// RUN: %target-swift-frontend -emit-ir -profile-generate -profile-coverage-mapping -Xcc -fprofile-instr-generate -Xcc -fcoverage-mapping -I %S/Inputs/issue-57483 %s | %FileCheck %s
+// RUN: %target-swift-frontend -emit-ir -profile-generate -profile-coverage-mapping -Xcc -fprofile-instr-generate -Xcc -fcoverage-mapping -I %S/Inputs/CModule %s | %FileCheck %s
 
 // https://github.com/apple/swift/issues/57483 (rdar://82820628)
-// Make sure we don't crash in IRGen attempting to emit the coverage map for the
-// implicit Clang getter for the member bitfield.
-
-// CHECK: define {{.*}} @"$So7cstructV$member$getter"
+// Make sure we don't crash in IRGen attempting to emit the coverage map for any
+// implicit Clang decls.
 
 import CModule
 
-func foo(_ x: UnsafePointer<cstruct>?) {
+func testStruct(_ x: UnsafePointer<cstruct>?) {
   _ = x?.pointee.member
+  _ = cstruct()
+  _ = cstruct(member: 5)
 }
-foo(nil)
+testStruct(nil)
+
+// CHECK: define {{.*}} @"$So7cstructV$member$setter"
+// CHECK: define {{.*}} @"$So7cstructV$member$getter"