[HLSL] Introduce address space hlsl_constant(2) for constant buffer declarations (#123411)

Introduces a new address space `hlsl_constant(2)` for constant buffer
declarations.

This address space is applied to declarations inside `cbuffer` block.
Later on, it will also be applied to `ConstantBuffer<T>` syntax and the
default `$Globals` constant buffer.

Clang codegen translates constant buffer declarations to global
variables and loads from `hlsl_constant(2)` address space. More work
coming soon will include addition of metadata that will map these
globals to individual constant buffers and enable their transformation
to appropriate constant buffer load intrinsics later on in an LLVM pass.

Fixes #123406

Author: hekota

clang/include/clang/Basic/AddressSpaces.h

@@ -58,6 +58,7 @@ enum class LangAS : unsigned {
 
   // HLSL specific address spaces.
   hlsl_groupshared,
+  hlsl_constant,
 
   // Wasm specific address spaces.
   wasm_funcref,

clang/lib/AST/TypePrinter.cpp

@@ -2552,10 +2552,12 @@ std::string Qualifiers::getAddrSpaceAsString(LangAS AS) {
     return "__uptr __ptr32";
   case LangAS::ptr64:
     return "__ptr64";
-  case LangAS::wasm_funcref:
-    return "__funcref";
   case LangAS::hlsl_groupshared:
     return "groupshared";
+  case LangAS::hlsl_constant:
+    return "hlsl_constant";
+  case LangAS::wasm_funcref:
+    return "__funcref";
   default:
     return std::to_string(toTargetAddressSpace(AS));
   }

clang/lib/Basic/Targets/AArch64.h

@@ -44,6 +44,7 @@ static const unsigned ARM64AddrSpaceMap[] = {
     static_cast<unsigned>(AArch64AddrSpace::ptr32_uptr),
     static_cast<unsigned>(AArch64AddrSpace::ptr64),
     0, // hlsl_groupshared
+    0, // hlsl_constant
     // Wasm address space values for this target are dummy values,
     // as it is only enabled for Wasm targets.
     20, // wasm_funcref

clang/lib/Basic/Targets/AMDGPU.cpp

@@ -59,6 +59,7 @@ const LangASMap AMDGPUTargetInfo::AMDGPUDefIsGenMap = {
     llvm::AMDGPUAS::FLAT_ADDRESS,     // ptr32_uptr
     llvm::AMDGPUAS::FLAT_ADDRESS,     // ptr64
     llvm::AMDGPUAS::FLAT_ADDRESS,     // hlsl_groupshared
+    llvm::AMDGPUAS::CONSTANT_ADDRESS, // hlsl_constant
 };
 
 const LangASMap AMDGPUTargetInfo::AMDGPUDefIsPrivMap = {
@@ -74,16 +75,16 @@ const LangASMap AMDGPUTargetInfo::AMDGPUDefIsPrivMap = {
     llvm::AMDGPUAS::CONSTANT_ADDRESS, // cuda_constant
     llvm::AMDGPUAS::LOCAL_ADDRESS,    // cuda_shared
     // SYCL address space values for this map are dummy
-    llvm::AMDGPUAS::FLAT_ADDRESS, // sycl_global
-    llvm::AMDGPUAS::FLAT_ADDRESS, // sycl_global_device
-    llvm::AMDGPUAS::FLAT_ADDRESS, // sycl_global_host
-    llvm::AMDGPUAS::FLAT_ADDRESS, // sycl_local
-    llvm::AMDGPUAS::FLAT_ADDRESS, // sycl_private
-    llvm::AMDGPUAS::FLAT_ADDRESS, // ptr32_sptr
-    llvm::AMDGPUAS::FLAT_ADDRESS, // ptr32_uptr
-    llvm::AMDGPUAS::FLAT_ADDRESS, // ptr64
-    llvm::AMDGPUAS::FLAT_ADDRESS, // hlsl_groupshared
-
+    llvm::AMDGPUAS::FLAT_ADDRESS,     // sycl_global
+    llvm::AMDGPUAS::FLAT_ADDRESS,     // sycl_global_device
+    llvm::AMDGPUAS::FLAT_ADDRESS,     // sycl_global_host
+    llvm::AMDGPUAS::FLAT_ADDRESS,     // sycl_local
+    llvm::AMDGPUAS::FLAT_ADDRESS,     // sycl_private
+    llvm::AMDGPUAS::FLAT_ADDRESS,     // ptr32_sptr
+    llvm::AMDGPUAS::FLAT_ADDRESS,     // ptr32_uptr
+    llvm::AMDGPUAS::FLAT_ADDRESS,     // ptr64
+    llvm::AMDGPUAS::FLAT_ADDRESS,     // hlsl_groupshared
+    llvm::AMDGPUAS::CONSTANT_ADDRESS, // hlsl_constant
 };
 } // namespace targets
 } // namespace clang

clang/lib/Basic/Targets/DirectX.h

@@ -42,6 +42,7 @@ static const unsigned DirectXAddrSpaceMap[] = {
     0, // ptr32_uptr
     0, // ptr64
     3, // hlsl_groupshared
+    2, // hlsl_constant
     // Wasm address space values for this target are dummy values,
     // as it is only enabled for Wasm targets.
     20, // wasm_funcref

clang/lib/Basic/Targets/NVPTX.h

@@ -46,6 +46,7 @@ static const unsigned NVPTXAddrSpaceMap[] = {
     0, // ptr32_uptr
     0, // ptr64
     0, // hlsl_groupshared
+    0, // hlsl_constant
     // Wasm address space values for this target are dummy values,
     // as it is only enabled for Wasm targets.
     20, // wasm_funcref

clang/lib/Basic/Targets/SPIR.h

@@ -47,6 +47,7 @@ static const unsigned SPIRDefIsPrivMap[] = {
     0, // ptr32_uptr
     0, // ptr64
     0, // hlsl_groupshared
+    2, // hlsl_constant
     // Wasm address space values for this target are dummy values,
     // as it is only enabled for Wasm targets.
     20, // wasm_funcref
@@ -80,6 +81,7 @@ static const unsigned SPIRDefIsGenMap[] = {
     0, // ptr32_uptr
     0, // ptr64
     0, // hlsl_groupshared
+    0, // hlsl_constant
     // Wasm address space values for this target are dummy values,
     // as it is only enabled for Wasm targets.
     20, // wasm_funcref

clang/lib/Basic/Targets/SystemZ.h

@@ -42,6 +42,7 @@ static const unsigned ZOSAddressMap[] = {
     1, // ptr32_uptr
     0, // ptr64
     0, // hlsl_groupshared
+    0, // hlsl_constant
     0  // wasm_funcref
 };
 

clang/lib/Basic/Targets/TCE.h

@@ -51,6 +51,7 @@ static const unsigned TCEOpenCLAddrSpaceMap[] = {
     0, // ptr32_uptr
     0, // ptr64
     0, // hlsl_groupshared
+    0, // hlsl_constant
     // Wasm address space values for this target are dummy values,
     // as it is only enabled for Wasm targets.
     20, // wasm_funcref

clang/lib/Basic/Targets/WebAssembly.h

@@ -42,6 +42,7 @@ static const unsigned WebAssemblyAddrSpaceMap[] = {
     0,  // ptr32_uptr
     0,  // ptr64
     0,  // hlsl_groupshared
+    0,  // hlsl_constant
     20, // wasm_funcref
 };