[HIP] stop forcing the lang std in the driver

[scchan]

Summary

D103221 changed HIP's default to C++14, removing the driver logic to
force it into a different std.

Change-Id: I9f5220a7456687039b0bd3b3574f3124d3cc7665

[yaxunl]

LGTM. Thanks.

clang/lib/Driver/ToolChains/Clang.cpp

if (!types::isCXX(InputType)) {
       } else
         ImplyVCPPCVer = true;
     }
     else if (IsWindowsMSVC)
       ImplyVCPPCXXVer = true;
 
     Args.AddLastArg(CmdArgs, options::OPT_ftrigraphs,
                     options::OPT_fno_trigraphs);
-
-    // HIP headers has minimum C++ standard requirements. Therefore set the
-    // default language standard.
-    if (IsHIP)
-      CmdArgs.push_back(IsWindowsMSVC ? "-std=c++14" : "-std=c++11");
   }
 
   // GCC's behavior for -Wwrite-strings is a bit strange:
   //  * In C, this "warning flag" changes the types of string literals from
   //    'char[N]' to 'const char[N]', and thus triggers an unrelated warning
   //    for the discarded qualifier.
   //  * In C++, this is just a normal warning flag.
   //

clang/test/Driver/hip-std.hip

 // REQUIRES: x86-registered-target
 // REQUIRES: amdgpu-registered-target
 
 // RUN: %clang -### --target=x86_64-unknown-linux-gnu -offload-arch=gfx906 %s \
 // RUN:   2>&1 | FileCheck -check-prefixes=DEFAULT %s
-// DEFAULT: "-cc1"{{.*}}"-fcuda-is-device"{{.*}}"-std=c++11"
-// DEFAULT: "-cc1"{{.*}}"-std=c++11"
+// DEFAULT: "-cc1"{{.*}}"-fcuda-is-device"{{.*}}
+// DEFAULT-NOT: "-std="{{.*}}
+// DEFAULT: "-cc1"{{.*}}
+// DEFAULT-NOT: "-std="{{.*}}
 
 // RUN: %clang -### --target=x86_64-unknown-linux-gnu -offload-arch=gfx906 %s \
 // RUN:   -std=c++17 %s 2>&1 | FileCheck -check-prefixes=SPECIFIED %s
 // SPECIFIED: "-cc1"{{.*}}"-fcuda-is-device"{{.*}}"-std=c++17"
 // SPECIFIED: "-cc1"{{.*}}"-std=c++17"
 
 // RUN: %clang -### --target=x86_64-pc-windows-msvc -offload-arch=gfx906 %s \
 // RUN:   2>&1 | FileCheck -check-prefixes=MSVC-DEF %s
-// MSVC-DEF: "-cc1"{{.*}}"-fcuda-is-device"{{.*}}"-std=c++14"
-// MSVC-DEF: "-cc1"{{.*}}"-std=c++14"
+// MSVC-DEF: "-cc1"{{.*}}"-fcuda-is-device"{{.*}}
+// MSVC-DEF-NOT: "-std="{{.*}}
+// MSVC-DEF: "-cc1"{{.*}}
+// MSVC-DEF-NOT: "-std="{{.*}}
 
 // RUN: %clang -### --target=x86_64-pc-windows-msvc -offload-arch=gfx906 %s \
 // RUN:   -std=c++17 %s 2>&1 | FileCheck -check-prefixes=MSVC-SPEC %s
 // MSVC-SPEC: "-cc1"{{.*}}"-fcuda-is-device"{{.*}}"-std=c++17"
 // MSVC-SPEC: "-cc1"{{.*}}"-std=c++17"