remove callconv hack

Author: gwenzek

src/clang.zig

@@ -1788,7 +1788,6 @@ pub const CallingConv = enum(c_int) {
     PreserveMost,
     PreserveAll,
     AArch64VectorCall,
-    PtxKernel,
 };
 
 pub const StorageClass = enum(c_int) {

src/codegen/llvm.zig

@@ -4520,9 +4520,7 @@ fn toLlvmCallConv(cc: std.builtin.CallingConvention, target: std.Target) llvm.Ca
         .SysV => .X86_64_SysV,
         .PtxKernel => return switch (target.cpu.arch) {
             .nvptx, .nvptx64 => .PTX_Kernel,
-            // TODO: this doesn't work as expected, because it only changes
-            // the cc for LLVM, but not for the rest of the compiler
-            else => .Fast,
+            else => unreachable,
         },
     };
 }

src/stage1/analyze.cpp

@@ -1973,8 +1973,6 @@ Error emit_error_unless_callconv_allowed_for_target(CodeGen *g, AstNode *source_
         case CallingConventionNaked:
         case CallingConventionAsync:
         case CallingConventionInline:
-        case CallingConventionPtxKernel:
-            break;
         case CallingConventionInterrupt:
             if (g->zig_target->arch != ZigLLVM_x86
                 && g->zig_target->arch != ZigLLVM_x86_64
@@ -2011,6 +2009,14 @@ Error emit_error_unless_callconv_allowed_for_target(CodeGen *g, AstNode *source_
             if (g->zig_target->arch != ZigLLVM_x86_64)
                 allowed_platforms = "x86_64";
             break;
+      case CallingConventionPtxKernel:
+            if (g->zig_target->arch != ZigLLVM_nvptx
+                && g->zig_target->arch != ZigLLVM_nvptx64)
+            {
+                allowed_platforms = "nvptx and nvptx64";
+            }
+            break;
+
     }
     if (allowed_platforms != nullptr) {
         add_node_error(g, source_node, buf_sprintf(

src/stage1/codegen.cpp

@@ -210,10 +210,9 @@ static ZigLLVM_CallingConv get_llvm_cc(CodeGen *g, CallingConvention cc) {
             assert(g->zig_target->arch == ZigLLVM_x86_64);
             return ZigLLVM_X86_64_SysV;
         case CallingConventionPtxKernel:
-            if (g->zig_target->arch == ZigLLVM_nvptx ||
-                g->zig_target->arch == ZigLLVM_nvptx64)
+            assert(g->zig_target->arch == ZigLLVM_nvptx ||
+                g->zig_target->arch == ZigLLVM_nvptx64);
                 return ZigLLVM_PTX_Kernel;
-            return ZigLLVM_Fast;
 
     }
     zig_unreachable();