[OPENMP]Fix PR47158, case 2: do not report host-only functions in unused function in device mode.

[ABataev]

Summary

If the function is not marked exlicitly as declare target and it calls
function(s), marked as declare target device_type(host), these host-only
functions should be dignosed as used in device mode, if the caller
function is not used in device mode too.

[jdoerfert]

LGTM, nit: Is there a "not" missing in the the commit message?

[ABataev]

In D86164#2224577, @jdoerfert wrote:

LGTM, nit: Is there a "not" missing in the the commit message?

Yes, will add it, thanks!

clang/lib/Sema/Sema.cpp

public:
 
   void checkFunc(SourceLocation Loc, FunctionDecl *FD) {
     auto &Done = DoneMap[InOMPDeviceContext > 0 ? 1 : 0];
     FunctionDecl *Caller = UsePath.empty() ? nullptr : UsePath.back();
     if ((!ShouldEmitRootNode && !S.getLangOpts().OpenMP && !Caller) ||
         S.shouldIgnoreInHostDeviceCheck(FD) || InUsePath.count(FD))
       return;
     // Finalize analysis of OpenMP-specific constructs.
-    if (Caller && S.LangOpts.OpenMP && UsePath.size() == 1)
+    if (Caller && S.LangOpts.OpenMP && UsePath.size() == 1 &&
+        (ShouldEmitRootNode || InOMPDeviceContext))
       S.finalizeOpenMPDelayedAnalysis(Caller, FD, Loc);
     if (Caller)
       S.DeviceKnownEmittedFns[FD] = {Caller, Loc};
     // Always emit deferred diagnostics for the direct users. This does not
     // lead to explosion of diagnostics since each user is visited at most
     // twice.
     if (ShouldEmitRootNode || InOMPDeviceContext)
       emitDeferredDiags(FD, Caller);

clang/test/OpenMP/declare_target_messages.cpp

 #pragma omp declare target link(x) // expected-error {{'x' must not appear in both clauses 'to' and 'link'}}
 
 void bazz() {}
 #pragma omp declare target to(bazz) device_type(nohost) // omp45-error {{unexpected 'device_type' clause, only 'to' or 'link' clauses expected}} host5-note 3{{marked as 'device_type(nohost)' here}}
 void bazzz() {bazz();}
 #pragma omp declare target to(bazzz) device_type(nohost) // omp45-error {{unexpected 'device_type' clause, only 'to' or 'link' clauses expected}}
 void any() {bazz();} // host5-error {{function with 'device_type(nohost)' is not available on host}}
 void host1() {bazz();} // host5-error {{function with 'device_type(nohost)' is not available on host}}
-#pragma omp declare target to(host1) device_type(host) // omp45-error {{unexpected 'device_type' clause, only 'to' or 'link' clauses expected}} dev5-note 4 {{marked as 'device_type(host)' here}}
+#pragma omp declare target to(host1) device_type(host) // omp45-error {{unexpected 'device_type' clause, only 'to' or 'link' clauses expected}} dev5-note 3 {{marked as 'device_type(host)' here}}
 void host2() {bazz();} //host5-error {{function with 'device_type(nohost)' is not available on host}}
 #pragma omp declare target to(host2)
 void device() {host1();} // dev5-error {{function with 'device_type(host)' is not available on device}}
 #pragma omp declare target to(device) device_type(nohost) // omp45-error {{unexpected 'device_type' clause, only 'to' or 'link' clauses expected}} host5-note 2 {{marked as 'device_type(nohost)' here}}
 void host3() {host1();} // dev5-error {{function with 'device_type(host)' is not available on device}}
 #pragma omp declare target to(host3)
 
 #pragma omp declare target
 void any1() {any();}
 void any2() {host1();} // dev5-error {{function with 'device_type(host)' is not available on device}}
 void any3() {device();} // host5-error {{function with 'device_type(nohost)' is not available on host}}
 void any4() {any2();}
 #pragma omp end declare target
 
 void any5() {any();}
-void any6() {host1();} // dev5-error {{function with 'device_type(host)' is not available on device}}
+void any6() {host1();}
 void any7() {device();} // host5-error {{function with 'device_type(nohost)' is not available on host}}
 void any8() {any2();}
 
 #pragma omp declare target // expected-error {{expected '#pragma omp end declare target'}} expected-note {{to match this '#pragma omp declare target'}}