[PATCH] D80450: [CUDA][HIP] Fix implicit HD function resolution

[Yaxun Liu via Phabricator via cfe-commits]

yaxunl created this revision.
yaxunl added a reviewer: tra.

When implicit HD function calls a function in device compilation,
if one candidate is an implicit HD function, current solution rule is:

D wins over HD and H
HD and H are equal

this caused regression when there is an otherwise worse D candidate

This patch changes that to

D, HD and H are all equal

The rationale is that we already know for host compilation there is already
a valid candidate in HD and H candidates that will not cause error. Allowing
HD and H gives us a fall back candidate that will not cause error. If D wins,
that means D has to be a better match otherwise, therefore D should also
be a valid candidate that will not cause error. In this way, we can guarantee
no regression.


https://reviews.llvm.org/D80450

Files:
  clang/lib/Sema/SemaOverload.cpp
  clang/test/SemaCUDA/function-overload.cu


Index: clang/test/SemaCUDA/function-overload.cu
===================================================================
--- clang/test/SemaCUDA/function-overload.cu
+++ clang/test/SemaCUDA/function-overload.cu
@@ -541,3 +541,51 @@
   }
 };
 }
+
+// Implicit HD candidate competes with device candidate.
+// a and b have implicit HD copy ctor. In copy ctor of b, ctor of a is resolved.
+// copy ctor of a should win over a(short), otherwise there will be ambiguity
+// due to conversion operator.
+namespace TestImplicitHDWithD {
+  struct a {
+    __attribute__((device)) a(short);
+    __attribute__((device)) operator unsigned() const;
+    __attribute__((device)) operator int() const;
+  };
+  struct b {
+    a d;
+  };
+  void f(b g) { b e = g; }
+}
+
+// Implicit HD candidate competes with host candidate.
+// a and b have implicit HD copy ctor. In copy ctor of b, ctor of a is resolved.
+// copy ctor of a should win over a(short), otherwise there will be ambiguity
+// due to conversion operator.
+namespace TestImplicitHDWithH {
+  struct a {
+    a(short);
+    __attribute__((device)) operator unsigned() const;
+    __attribute__((device)) operator int() const;
+  };
+  struct b {
+    a d;
+  };
+  void f(b g) { b e = g; }
+}
+
+// Implicit HD candidate comptes with HD candidate.
+// a and b have implicit HD copy ctor. In copy ctor of b, ctor of a is resolved.
+// copy ctor of a should win over a(short), otherwise there will be ambiguity
+// due to conversion operator.
+namespace TestImplicitHDWithHD {
+  struct a {
+    __attribute__((host,device)) a(short);
+    __attribute__((device)) operator unsigned() const;
+    __attribute__((device)) operator int() const;
+  };
+  struct b {
+    a d;
+  };
+  void f(b g) { b e = g; }
+}
Index: clang/lib/Sema/SemaOverload.cpp
===================================================================
--- clang/lib/Sema/SemaOverload.cpp
+++ clang/lib/Sema/SemaOverload.cpp
@@ -9534,7 +9534,7 @@
       auto EmitThreshold =
           (S.getLangOpts().CUDAIsDevice && IsCallerImplicitHD &&
            (IsCand1ImplicitHD || IsCand2ImplicitHD))
-              ? Sema::CFP_HostDevice
+              ? Sema::CFP_Never
               : Sema::CFP_WrongSide;
       auto Cand1Emittable = P1 > EmitThreshold;
       auto Cand2Emittable = P2 > EmitThreshold;


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