Expose clang option `-fdiagnostics-format=` in dxc (#6357)

This change exposes the clang 3.7 `-fdiagnostics-format=` flag in DXC with supported values `clang`, `msvc`, `mdvc-fallback`, and `vi`.

This option allows having DXC output diagnostic messages in string formats that are recognized natively by Visual Studio.

Resolves #6160 & #1811, both of which had been closed as not planned.

include/dxc/Support/HLSLOptions.h

@@ -156,6 +156,7 @@ public:
   llvm::StringRef DefaultLinkage;             // OPT_default_linkage
   llvm::StringRef ImportBindingTable;         // OPT_import_binding_table
   llvm::StringRef BindingTableDefine;         // OPT_binding_table_define
+  llvm::StringRef DiagnosticsFormat;          // OPT_fdiagnostics_format
   unsigned DefaultTextCodePage = DXC_CP_UTF8; // OPT_encoding
 
   bool AllResourcesBound = false;         // OPT_all_resources_bound

include/dxc/Support/HLSLOptions.td

@@ -121,6 +121,9 @@ def fconstexpr_depth_EQ : Joined<["-"], "fconstexpr-depth=">, Group<f_Group>;
 def fconstexpr_steps_EQ : Joined<["-"], "fconstexpr-steps=">, Group<f_Group>;
 def fconstexpr_backtrace_limit_EQ : Joined<["-"], "fconstexpr-backtrace-limit=">,
                                     Group<f_Group>;
+def fdiagnostics_format_EQ : Joined<["-"], "fdiagnostics-format=">, Group<hlslcomp_Group>,
+    Flags<[CoreOption]>,
+    HelpText<"Select diagnostic message format. Supported values: clang, msvc, mdvc-fallback, vi">;
 def fdiagnostics_show_option : Flag<["-"], "fdiagnostics-show-option">, Group<hlslcomp_Group>,
     Flags<[CoreOption]>, HelpText<"Print option name with mappable diagnostics">;
 def fno_diagnostics_show_option : Flag<["-"], "fno-diagnostics-show-option">, Group<hlslcomp_Group>,

lib/DxcSupport/HLSLOptions.cpp

@@ -538,6 +538,8 @@ int ReadDxcOpts(const OptTable *optionTable, unsigned flagsToInclude,
   opts.OutputReflectionFile = Args.getLastArgValue(OPT_Fre);
   opts.OutputRootSigFile = Args.getLastArgValue(OPT_Frs);
   opts.OutputShaderHashFile = Args.getLastArgValue(OPT_Fsh);
+  opts.DiagnosticsFormat =
+      Args.getLastArgValue(OPT_fdiagnostics_format_EQ, "clang");
   opts.ShowOptionNames = Args.hasFlag(OPT_fdiagnostics_show_option,
                                       OPT_fno_diagnostics_show_option, true);
   opts.UseColor = Args.hasFlag(OPT_Cc, OPT_INVALID, false);

tools/clang/test/DXC/fdiagnostics-format.test

@@ -0,0 +1,14 @@
+// RUN: %dxc -T ps_6_0 %s -verify
+// RUN: not %dxc -T ps_6_0 %s 2>&1 | FileCheck %s --check-prefix=CLANG
+// RUN: not %dxc -T ps_6_0 %s -fdiagnostics-format=clang 2>&1 | FileCheck %s --check-prefix=CLANG
+// RUN: not %dxc -T ps_6_0 %s -fdiagnostics-format=msvc 2>&1 | FileCheck %s --check-prefix=MSVC
+// RUN: not %dxc -T ps_6_0 %s -fdiagnostics-format=msvc-fallback 2>&1 | FileCheck %s --check-prefix=MSVC
+// RUN: not %dxc -T ps_6_0 %s -fdiagnostics-format=vi 2>&1 | FileCheck %s --check-prefix=VI
+// RUN: not %dxc -T ps_6_0 %s -fdiagnostics-format=nonsense 2>&1 | FileCheck %s --check-prefixes=NONSENSE,CLANG
+
+main() {} // expected-error{{HLSL requires a type specifier for all declarations}}
+
+// NONSENSE: warning: invalid option nonsense to -fdiagnostics-format: supported values are clang, msvc, msvc-fallback, and vi
+// VI: +9:1: error: HLSL requires a type specifier for all declarations
+// MSVC: (9,1) :  error: HLSL requires a type specifier for all declarations
+// CLANG: :9:1: error: HLSL requires a type specifier for all declarations

tools/clang/tools/dxcompiler/dxcompilerobj.cpp

@@ -1359,6 +1359,18 @@ public:
     compiler.createDiagnostics(diagPrinter, false);
     // don't output warning to stderr/file if "/no-warnings" is present.
     compiler.getDiagnostics().setIgnoreAllWarnings(!Opts.OutputWarnings);
+    if (Opts.DiagnosticsFormat.equals_lower("msvc") ||
+        Opts.DiagnosticsFormat.equals_lower("msvc-fallback"))
+      compiler.getDiagnosticOpts().setFormat(DiagnosticOptions::MSVC);
+    else if (Opts.DiagnosticsFormat.equals_lower("vi"))
+      compiler.getDiagnosticOpts().setFormat(DiagnosticOptions::Vi);
+    else if (!Opts.DiagnosticsFormat.equals_lower("clang")) {
+      auto const ID = compiler.getDiagnostics().getCustomDiagID(
+          clang::DiagnosticsEngine::Warning,
+          "invalid option %0 to -fdiagnostics-format: supported values are "
+          "clang, msvc, msvc-fallback, and vi");
+      compiler.getDiagnostics().Report(ID) << Opts.DiagnosticsFormat;
+    }
     compiler.createFileManager();
     compiler.createSourceManager(compiler.getFileManager());
     compiler.setTarget(