[linux-port] Fix a handful of warnings in headers (#1299)

Just a few warning conditions in a handful of common headers
was producing pages and pages of warning messages. By fixing them,
the output spew is reduced significantly.

Static variables in a header produce a separate variable for every
file that includes it. In many of these, these variables were unused.
Instead, variables used in multiple files should be defined only
once in a source file and declared as extern in the header.

Many unsigned variables were checked to be greater than zero and less
than 3 in HlslTypes.h. If they were somehow assigned a negative
value, it would appear as much greater than 3 in unsigned form.
So we can just check that they are less than or equal to 3.

In Type.h, parammods_begin() was casting its return value to the
proper pointer, but without const, producing an error. The best
part is that the function returned a const pointer. The cast was
just wrong. Adding const silences the warning.

include/dxc/HLSL/DxilConstants.h

@@ -965,22 +965,12 @@ namespace DXIL {
   };
 
 
-  // TODO: revisit data layout descriptions for the following:
-  //      - x64 pointers?
-  //      - Keep elf manging(m:e)?
-
-  // For legacy data layout, everything less than 32 align to 32.
-  static const char* kLegacyLayoutString = "e-m:e-p:32:32-i1:32-i8:32-i16:32-i32:32-i64:64-f16:32-f32:32-f:64:64-n8:16:32:64";
-
-  // New data layout with native low precision types
-  static const char* kNewLayoutString = "e-m:e-p:32:32-i1:32-i8:8-i16:16-i32:32-i64:64-f16:16-f32:32-f64:64-n8:16:32:64";
-
-  // Function Attributes
-  // TODO: consider generating attributes from hctdb
-  static const char* kFP32DenormKindString          = "fp32-denorm-mode";
-  static const char* kFP32DenormValueAnyString      = "any";
-  static const char* kFP32DenormValuePreserveString = "preserve";
-  static const char* kFP32DenormValueFtzString      = "ftz";
+  extern const char* kLegacyLayoutString;
+  extern const char* kNewLayoutString;
+  extern const char* kFP32DenormKindString;
+  extern const char* kFP32DenormValueAnyString;
+  extern const char* kFP32DenormValuePreserveString;
+  extern const char* kFP32DenormValueFtzString;
 
 } // namespace DXIL
 

tools/clang/include/clang/AST/HlslTypes.h

@@ -117,15 +117,15 @@ struct MatrixMemberAccessPositions {
     default:
     case 3: *row = R3_Row; *col = R3_Col; break;
     }
-    assert(0 <= *row && *row <= 3);
-    assert(0 <= *col && *col <= 3);
+    assert(*row <= 3);
+    assert(*col <= 3);
   }
 
   void SetPosition(uint32_t index, uint32_t row, uint32_t col)
   {
     assert(index < 4);
-    assert(0 <= row && row <= 3);
-    assert(0 <= col && col <= 3);
+    assert(row <= 3);
+    assert(col <= 3);
     switch (index)
     {
     case 0: R0_Row = row; R0_Col = col; break;
@@ -168,13 +168,13 @@ struct VectorMemberAccessPositions {
     default:
     case 3: *col = Swz3; break;
     }
-    assert(0 <= *col && *col <= 3);
+    assert(*col <= 3);
   }
 
   void SetPosition(uint32_t index, uint32_t col)
   {
     assert(index < 4);
-    assert(0 <= col && col <= 3);
+    assert(col <= 3);
     switch (index)
     {
     case 0: Swz0 = col; break;

tools/clang/include/clang/AST/Type.h

@@ -3298,7 +3298,7 @@ public:
   }
   const hlsl::ParameterModifier *parammods_begin() const {
     // param modifiers begin where exceptions end
-    return (hlsl::ParameterModifier*)exception_end();
+    return (const hlsl::ParameterModifier*)exception_end();
   }
   const hlsl::ParameterModifier *parammods_end() const {
     // modifiers begin where arguments end (in place of exceptions, in HLSL)

tools/clang/lib/CodeGen/CGHLSLMS.cpp

@@ -53,6 +53,28 @@ using std::unique_ptr;
 
 static const bool KeepUndefinedTrue = true; // Keep interpolation mode undefined if not set explicitly.
 
+// Define constant variables exposed in DxilConstants.h
+namespace hlsl {
+namespace DXIL {
+  // TODO: revisit data layout descriptions for the following:
+  //      - x64 pointers?
+  //      - Keep elf manging(m:e)?
+
+  // For legacy data layout, everything less than 32 align to 32.
+  const char* kLegacyLayoutString = "e-m:e-p:32:32-i1:32-i8:32-i16:32-i32:32-i64:64-f16:32-f32:32-f:64:64-n8:16:32:64";
+
+  // New data layout with native low precision types
+  const char* kNewLayoutString = "e-m:e-p:32:32-i1:32-i8:8-i16:16-i32:32-i64:64-f16:16-f32:32-f64:64-n8:16:32:64";
+
+  // Function Attributes
+  // TODO: consider generating attributes from hctdb
+  const char* kFP32DenormKindString          = "fp32-denorm-mode";
+  const char* kFP32DenormValueAnyString      = "any";
+  const char* kFP32DenormValuePreserveString = "preserve";
+  const char* kFP32DenormValueFtzString      = "ftz";
+} // DXIL
+} // hlsl
+
 namespace {
 
 /// Use this class to represent HLSL cbuffer in high-level DXIL.