[clang][CUDA] Disable float128 diagnostics for device compilation (#83918)

Author: pranavk

clang/lib/Sema/SemaDeclAttr.cpp

@@ -4877,7 +4877,9 @@ void Sema::AddModeAttr(Decl *D, const AttributeCommonInfo &CI,
     NewElemTy = Context.getRealTypeForBitwidth(DestWidth, ExplicitType);
 
   if (NewElemTy.isNull()) {
-    Diag(AttrLoc, diag::err_machine_mode) << 1 /*Unsupported*/ << Name;
+    // Only emit diagnostic on host for 128-bit mode attribute
+    if (!(DestWidth == 128 && getLangOpts().CUDAIsDevice))
+      Diag(AttrLoc, diag::err_machine_mode) << 1 /*Unsupported*/ << Name;
     return;
   }
 

clang/lib/Sema/SemaType.cpp

@@ -1561,7 +1561,7 @@ static QualType ConvertDeclSpecToType(TypeProcessingState &state) {
     break;
   case DeclSpec::TST_float128:
     if (!S.Context.getTargetInfo().hasFloat128Type() &&
-        !S.getLangOpts().SYCLIsDevice &&
+        !S.getLangOpts().SYCLIsDevice && !S.getLangOpts().CUDAIsDevice &&
         !(S.getLangOpts().OpenMP && S.getLangOpts().OpenMPIsTargetDevice))
       S.Diag(DS.getTypeSpecTypeLoc(), diag::err_type_unsupported)
         << "__float128";

clang/test/SemaCUDA/float128.cu

@@ -0,0 +1,18 @@
+// CPU-side compilation on x86 (no errors expected).
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -aux-triple nvptx64 -x cuda -fsyntax-only -verify=cpu %s
+
+// GPU-side compilation on x86 (no errors expected)
+// RUN: %clang_cc1 -triple nvptx64 -aux-triple x86_64-unknown-linux-gnu -fcuda-is-device -x cuda -fsyntax-only -verify=gpu %s
+
+// cpu-no-diagnostics
+typedef _Complex float __cfloat128 __attribute__ ((__mode__ (__TC__)));
+typedef __float128 _Float128;
+
+// gpu-note@+1 {{'a' defined here}}
+__attribute__((device)) __float128 f(__float128 a, float b) {
+    // gpu-note@+1 {{'c' defined here}}
+  __float128 c = b + 1.0;
+  // gpu-error@+2 {{'a' requires 128 bit size '__float128' type support, but target 'nvptx64' does not support it}}
+  // gpu-error@+1 {{'c' requires 128 bit size '__float128' type support, but target 'nvptx64' does not support it}}
+  return a + c;
+}