Index: clang/lib/Basic/Targets/AMDGPU.h
===================================================================
--- clang/lib/Basic/Targets/AMDGPU.h
+++ clang/lib/Basic/Targets/AMDGPU.h
@@ -41,6 +41,7 @@
 
   llvm::AMDGPU::GPUKind GPUKind;
   unsigned GPUFeatures;
+  unsigned WavefrontSize;
 
   /// Target ID is device name followed by optional feature name postfixed
   /// by plus or minus sign delimitted by colon, e.g. gfx908:xnack+:sram-ecc-.
@@ -407,6 +408,8 @@
         getAllPossibleTargetIDFeatures(getTriple(), getArchNameAMDGCN(GPUKind));
     llvm::for_each(Features, [&](const auto &F) {
       assert(F.front() == '+' || F.front() == '-');
+      if (F == "+wavefrontsize64")
+        WavefrontSize = 64;
       bool IsOn = F.front() == '+';
       StringRef Name = StringRef(F).drop_front();
       if (llvm::find(TargetIDFeatures, Name) == TargetIDFeatures.end())
Index: clang/lib/Basic/Targets/AMDGPU.cpp
===================================================================
--- clang/lib/Basic/Targets/AMDGPU.cpp
+++ clang/lib/Basic/Targets/AMDGPU.cpp
@@ -316,6 +316,7 @@
 
   HasLegalHalfType = true;
   HasFloat16 = true;
+  WavefrontSize = GPUFeatures & llvm::AMDGPU::FEATURE_WAVE32 ? 32 : 64;
 
   // Set pointer width and alignment for target address space 0.
   PointerWidth = PointerAlign = DataLayout->getPointerSizeInBits();
@@ -388,6 +389,8 @@
     Builder.defineMacro("__HAS_FP64__");
   if (hasFastFMA())
     Builder.defineMacro("FP_FAST_FMA");
+
+  Builder.defineMacro("__AMDGCN_WAVEFRONT_SIZE", Twine(WavefrontSize));
 }
 
 void AMDGPUTargetInfo::setAuxTarget(const TargetInfo *Aux) {
Index: clang/lib/Driver/ToolChains/AMDGPU.cpp
===================================================================
--- clang/lib/Driver/ToolChains/AMDGPU.cpp
+++ clang/lib/Driver/ToolChains/AMDGPU.cpp
@@ -390,15 +390,19 @@
     }
   }
 
-  if (Args.getLastArg(options::OPT_mwavefrontsize64)) {
-    Features.push_back("-wavefrontsize16");
-    Features.push_back("-wavefrontsize32");
-    Features.push_back("+wavefrontsize64");
-  }
-  if (Args.getLastArg(options::OPT_mno_wavefrontsize64)) {
-    Features.push_back("-wavefrontsize16");
-    Features.push_back("+wavefrontsize32");
-    Features.push_back("-wavefrontsize64");
+  // Get the last argument of -mwavefrontsize64 or -mno-wavefrontsize64.
+  for (auto WaveArg : Args.filtered_reverse(options::OPT_mwavefrontsize64,
+                                            options::OPT_mno_wavefrontsize64)) {
+    if (WaveArg->getOption().getID() == options::OPT_mwavefrontsize64) {
+      Features.push_back("-wavefrontsize16");
+      Features.push_back("-wavefrontsize32");
+      Features.push_back("+wavefrontsize64");
+    } else {
+      Features.push_back("-wavefrontsize16");
+      Features.push_back("+wavefrontsize32");
+      Features.push_back("-wavefrontsize64");
+    }
+    break;
   }
 
   handleTargetFeaturesGroup(
Index: clang/test/Driver/amdgpu-features.c
===================================================================
--- clang/test/Driver/amdgpu-features.c
+++ clang/test/Driver/amdgpu-features.c
@@ -25,9 +25,11 @@
 // NO-SRAM-ECC: "-target-feature" "-sram-ecc"
 
 // RUN: %clang -### -target amdgcn-amdpal -mcpu=gfx1010 -mwavefrontsize64 %s 2>&1 | FileCheck --check-prefix=WAVE64 %s
+// RUN: %clang -### -target amdgcn-amdpal -mcpu=gfx1010 -mno-wavefrontsize64 -mwavefrontsize64 %s 2>&1 | FileCheck --check-prefix=WAVE64 %s
 // WAVE64: "-target-feature" "-wavefrontsize16" "-target-feature" "-wavefrontsize32" "-target-feature" "+wavefrontsize64"
 
 // RUN: %clang -### -target amdgcn -mcpu=gfx1010 -mno-wavefrontsize64 %s 2>&1 | FileCheck --check-prefix=NO-WAVE64 %s
+// RUN: %clang -### -target amdgcn -mcpu=gfx1010 -mwavefrontsize64 -mno-wavefrontsize64 %s 2>&1 | FileCheck --check-prefix=NO-WAVE64 %s
 // NO-WAVE64: "-target-feature" "-wavefrontsize16" "-target-feature" "+wavefrontsize32" "-target-feature" "-wavefrontsize64"
 
 // RUN: %clang -### -target amdgcn -mcpu=gfx1010 -mcumode %s 2>&1 | FileCheck --check-prefix=CUMODE %s
Index: clang/test/Driver/amdgpu-macros.cl
===================================================================
--- clang/test/Driver/amdgpu-macros.cl
+++ clang/test/Driver/amdgpu-macros.cl
@@ -346,4 +346,42 @@
 // GFX1011-DAG: #define __amdgcn_processor__ "gfx1011"
 // GFX1012-DAG: #define __amdgcn_processor__ "gfx1012"
 // GFX1030-DAG: #define __amdgcn_processor__ "gfx1030"
-// GFX1031-DAG: #define __amdgcn_processor__ "gfx1031"
\ No newline at end of file
+// GFX1031-DAG: #define __amdgcn_processor__ "gfx1031"
+
+// GFX600-DAG: #define __AMDGCN_WAVEFRONT_SIZE 64
+// GFX601-DAG: #define __AMDGCN_WAVEFRONT_SIZE 64
+// GFX700-DAG: #define __AMDGCN_WAVEFRONT_SIZE 64
+// GFX701-DAG: #define __AMDGCN_WAVEFRONT_SIZE 64
+// GFX702-DAG: #define __AMDGCN_WAVEFRONT_SIZE 64
+// GFX703-DAG: #define __AMDGCN_WAVEFRONT_SIZE 64
+// GFX704-DAG: #define __AMDGCN_WAVEFRONT_SIZE 64
+// GFX801-DAG: #define __AMDGCN_WAVEFRONT_SIZE 64
+// GFX802-DAG: #define __AMDGCN_WAVEFRONT_SIZE 64
+// GFX803-DAG: #define __AMDGCN_WAVEFRONT_SIZE 64
+// GFX810-DAG: #define __AMDGCN_WAVEFRONT_SIZE 64
+// GFX900-DAG: #define __AMDGCN_WAVEFRONT_SIZE 64
+// GFX902-DAG: #define __AMDGCN_WAVEFRONT_SIZE 64
+// GFX904-DAG: #define __AMDGCN_WAVEFRONT_SIZE 64
+// GFX906-DAG: #define __AMDGCN_WAVEFRONT_SIZE 64
+// GFX908-DAG: #define __AMDGCN_WAVEFRONT_SIZE 64
+// GFX909-DAG: #define __AMDGCN_WAVEFRONT_SIZE 64
+// GFX1010-DAG: #define __AMDGCN_WAVEFRONT_SIZE 32
+// GFX1011-DAG: #define __AMDGCN_WAVEFRONT_SIZE 32
+// GFX1012-DAG: #define __AMDGCN_WAVEFRONT_SIZE 32
+// GFX1030-DAG: #define __AMDGCN_WAVEFRONT_SIZE 32
+// GFX1031-DAG: #define __AMDGCN_WAVEFRONT_SIZE 32
+
+// RUN: %clang -E -dM -target amdgcn -mcpu=gfx906 -mwavefrontsize64 \
+// RUN:   %s 2>&1 | FileCheck --check-prefixes=WAVE64 %s
+// RUN: %clang -E -dM -target amdgcn -mcpu=gfx1010 -mwavefrontsize64 \
+// RUN:   %s 2>&1 | FileCheck --check-prefixes=WAVE64 %s
+// RUN: %clang -E -dM -target amdgcn -mcpu=gfx906 -mwavefrontsize64 \
+// RUN:   -mno-wavefrontsize64 %s 2>&1 | FileCheck --check-prefixes=WAVE64 %s
+// RUN: %clang -E -dM -target amdgcn -mcpu=gfx1010 -mwavefrontsize64 \
+// RUN:   -mno-wavefrontsize64 %s 2>&1 | FileCheck --check-prefixes=WAVE32 %s
+// RUN: %clang -E -dM -target amdgcn -mcpu=gfx906 -mno-wavefrontsize64 \
+// RUN:   -mwavefrontsize64 %s 2>&1 | FileCheck --check-prefixes=WAVE64 %s
+// RUN: %clang -E -dM -target amdgcn -mcpu=gfx1010 -mno-wavefrontsize64 \
+// RUN:   -mwavefrontsize64 %s 2>&1 | FileCheck --check-prefixes=WAVE64 %s
+// WAVE64-DAG: #define __AMDGCN_WAVEFRONT_SIZE 64
+// WAVE32-DAG: #define __AMDGCN_WAVEFRONT_SIZE 32
Index: clang/test/Driver/hip-macros.hip
===================================================================
--- /dev/null
+++ clang/test/Driver/hip-macros.hip
@@ -0,0 +1,20 @@
+// RUN: %clang -E -dM --offload-arch=gfx906 -mwavefrontsize64 \
+// RUN:   --cuda-device-only -nogpuinc -nogpulib \
+// RUN:   %s 2>&1 | FileCheck --check-prefixes=WAVE64 %s
+// RUN: %clang -E -dM --offload-arch=gfx1010 -mwavefrontsize64 \
+// RUN:   --cuda-device-only -nogpuinc -nogpulib \
+// RUN:   %s 2>&1 | FileCheck --check-prefixes=WAVE64 %s
+// RUN: %clang -E -dM --offload-arch=gfx906 -mwavefrontsize64 \
+// RUN:   --cuda-device-only -nogpuinc -nogpulib \
+// RUN:   -mno-wavefrontsize64 %s 2>&1 | FileCheck --check-prefixes=WAVE64 %s
+// RUN: %clang -E -dM --offload-arch=gfx1010 -mwavefrontsize64 \
+// RUN:   --cuda-device-only -nogpuinc -nogpulib \
+// RUN:   -mno-wavefrontsize64 %s 2>&1 | FileCheck --check-prefixes=WAVE32 %s
+// RUN: %clang -E -dM --offload-arch=gfx906 -mno-wavefrontsize64 \
+// RUN:   --cuda-device-only -nogpuinc -nogpulib \
+// RUN:   -mwavefrontsize64 %s 2>&1 | FileCheck --check-prefixes=WAVE64 %s
+// RUN: %clang -E -dM --offload-arch=gfx1010 -mno-wavefrontsize64 \
+// RUN:   --cuda-device-only -nogpuinc -nogpulib \
+// RUN:   -mwavefrontsize64 %s 2>&1 | FileCheck --check-prefixes=WAVE64 %s
+// WAVE64-DAG: #define __AMDGCN_WAVEFRONT_SIZE 64
+// WAVE32-DAG: #define __AMDGCN_WAVEFRONT_SIZE 32
Index: clang/test/Driver/hip-toolchain-features.hip
===================================================================
--- clang/test/Driver/hip-toolchain-features.hip
+++ clang/test/Driver/hip-toolchain-features.hip
@@ -42,3 +42,12 @@
 // DUP-SAME: "-target-feature" "-wavefrontsize64"
 // DUP-SAME: "-target-feature" "+cumode"
 // DUP: {{.*}}lld{{.*}} "-plugin-opt=-mattr=-wavefrontsize16,+wavefrontsize32,-wavefrontsize64,+cumode"
+
+// RUN: %clang -### -target x86_64-linux-gnu -fgpu-rdc -nogpulib \
+// RUN:   --cuda-gpu-arch=gfx1010 %s \
+// RUN:   -mno-wavefrontsize64 -mwavefrontsize64 2>&1 \
+// RUN:   | FileCheck %s -check-prefix=WAVE64
+// WAVE64: {{.*}}clang{{.*}} "-target-feature" "-wavefrontsize16"
+// WAVE64-SAME: "-target-feature" "-wavefrontsize32"
+// WAVE64-SAME: "-target-feature" "+wavefrontsize64"
+// WAVE64: {{.*}}lld{{.*}} "-plugin-opt=-mattr=-wavefrontsize16,-wavefrontsize32,+wavefrontsize64"