[HIP] Change default offload arch to gfx906

[yaxunl]

Summary

Change default offload arch to gfx906 since
it is the lowest officially supported offload
arch (https://docs.amd.com/bundle/ROCm-Release-Notes-v5.4/page/About_This_Document.html#d2e131).

clang/lib/Driver/Driver.cpp

class HIPActionBuilder final : public CudaActionBuilderBase {
     // only compilation. Bundle other type of output files only if
     // --gpu-bundle-output is specified for device only compilation.
     std::optional<bool> BundleOutput;
 
   public:
     HIPActionBuilder(Compilation &C, DerivedArgList &Args,
                      const Driver::InputList &Inputs)
         : CudaActionBuilderBase(C, Args, Inputs, Action::OFK_HIP) {
-      DefaultCudaArch = CudaArch::GFX803;
+      DefaultCudaArch = CudaArch::GFX906;
       if (Args.hasArg(options::OPT_gpu_bundle_output,
                       options::OPT_no_gpu_bundle_output))
         BundleOutput = Args.hasFlag(options::OPT_gpu_bundle_output,
                                     options::OPT_no_gpu_bundle_output, true);
     }
 
     bool canUseBundlerUnbundler() const override { return true; }
 

clang/test/Driver/cuda-flush-denormals-to-zero.cu

 // RUN: %clang -x hip -### --target=x86_64-linux-gnu -c -march=haswell --cuda-gpu-arch=gfx803 -fno-gpu-flush-denormals-to-zero -nocudainc -nogpulib %s 2>&1 | FileCheck -check-prefix=NOFTZ %s
 
 // RUN: %clang -x hip -### --target=x86_64-linux-gnu -c -march=haswell --cuda-gpu-arch=gfx900 -fgpu-flush-denormals-to-zero -nocudainc -nogpulib %s 2>&1 | FileCheck -check-prefix=FTZ %s
 // RUN: %clang -x hip -### --target=x86_64-linux-gnu -c -march=haswell --cuda-gpu-arch=gfx900 -fno-gpu-flush-denormals-to-zero -nocudainc -nogpulib %s 2>&1 | FileCheck -check-prefix=NOFTZ %s
 
 // Test the default changing with no argument based on the subtarget in HIP mode
 // RUN: %clang -x hip -### --target=x86_64-linux-gnu -c -march=haswell --cuda-gpu-arch=gfx803 -nocudainc -nogpulib %s 2>&1 | FileCheck -check-prefix=FTZ %s
 // RUN: %clang -x hip -### --target=x86_64-linux-gnu -c -march=haswell --cuda-gpu-arch=gfx900 -nocudainc -nogpulib %s 2>&1 | FileCheck -check-prefix=NOFTZ %s
+// RUN: %clang -x hip -### --target=x86_64-linux-gnu -c -march=haswell --cuda-gpu-arch=gfx906 -nocudainc -nogpulib %s 2>&1 | FileCheck -check-prefix=NOFTZ %s
 
-// Test no subtarget, which should get the denormal setting of the default gfx803
-// RUN: %clang -x hip -### --target=x86_64-linux-gnu -c -march=haswell -nocudainc -nogpulib %s 2>&1 | FileCheck -check-prefix=FTZ %s
+// Test no subtarget, which should get the denormal setting of the default gfx906
+// RUN: %clang -x hip -### --target=x86_64-linux-gnu -c -march=haswell -nocudainc -nogpulib %s 2>&1 | FileCheck -check-prefix=NOFTZ %s
 
 // Test multiple offload archs with different defaults.
 // RUN: %clang -x hip -### --target=x86_64-linux-gnu -c -march=haswell --cuda-gpu-arch=gfx803 --cuda-gpu-arch=gfx900 -nocudainc -nogpulib %s 2>&1 | FileCheck -check-prefix=MIXED-DEFAULT-MODE %s
 // RUN: %clang -x hip -### --target=x86_64-linux-gnu -c -march=haswell -fgpu-flush-denormals-to-zero --cuda-gpu-arch=gfx803 --cuda-gpu-arch=gfx900 -nocudainc -nogpulib %s 2>&1 | FileCheck -check-prefix=FTZX2 %s
 // RUN: %clang -x hip -### --target=x86_64-linux-gnu -c -march=haswell -fno-gpu-flush-denormals-to-zero --cuda-gpu-arch=gfx803 --cuda-gpu-arch=gfx900 -nocudainc -nogpulib %s 2>&1 | FileCheck -check-prefix=NOFTZ %s
 
 
 // CPUFTZ-NOT: -fdenormal-fp-math

clang/test/Driver/hip-default-gpu-arch.hip

 // REQUIRES: x86-registered-target
 // REQUIRES: amdgpu-registered-target
 
 // RUN: %clang -### -c %s 2>&1 | FileCheck %s
 
-// CHECK: {{.*}}clang{{.*}}"-target-cpu" "gfx803"
+// CHECK: {{.*}}clang{{.*}}"-target-cpu" "gfx906"