[MLIR][SPIRV] Add flat, location, and noperspective decorations

[Hazem]

Summary

Add support for flat, location, and noperspective decorations in the serializer and deserializer to be able to process basic shader files for graphics applications"

[antiagainst]

Thanks @Hazem ! Just a few nits. Could you just name the test file as decorations.mlir to follow the terms in the spec?

mlir/test/Dialect/SPIRV/Serialization/decorators.mlir

4 ↗

(On Diff #267361)

Acutally I think we should // CHECK: location = 0: i32 instead of the spv.globalVariable here given that's the purpose of the test? :)

Similarly for the rest: // CHECK: no_perspective , // CHECK: flat?

[Hazem]

• rename decorations test file and edit CHECK string values to reflect what the tests actually check

mlir/lib/Dialect/SPIRV/Serialization/Deserializer.cpp

case spirv::Decoration::ArrayStride:
     if (words.size() != 3) {
       return emitError(unknownLoc, "OpDecorate with ")
              << decorationName << " needs a single integer literal";
     }
     typeDecorations[words[0]] = words[2];
     break;
   case spirv::Decoration::Block:
   case spirv::Decoration::BufferBlock:
+  case spirv::Decoration::Flat:
+  case spirv::Decoration::NoPerspective:
     if (words.size() != 2) {
       return emitError(unknownLoc, "OpDecoration with ")
              << decorationName << "needs a single target <id>";
     }
     // Block decoration does not affect spv.struct type, but is still stored for
     // verification.
     // TODO: Update StructType to contain this information since
     // it is needed for many validation rules.
     decorations[words[0]].set(symbol, opBuilder.getUnitAttr());
     break;
+  case spirv::Decoration::Location:
   case spirv::Decoration::SpecId:
     if (words.size() != 3) {
       return emitError(unknownLoc, "OpDecoration with ")
              << decorationName << "needs a single integer literal";
     }
     decorations[words[0]].set(
         symbol, opBuilder.getI32IntegerAttr(static_cast<int32_t>(words[2])));
     break;

mlir/lib/Dialect/SPIRV/Serialization/Serializer.cpp

LogicalResult Serializer::processDecoration(Location loc, uint32_t resultID,
   if (!decoration) {
     return emitError(
                loc, "non-argument attributes expected to have snake-case-ified "
                     "decoration name, unhandled attribute with name : ")
            << attrName;
   }
   SmallVector<uint32_t, 1> args;
   switch (decoration.getValue()) {
-  case spirv::Decoration::DescriptorSet:
   case spirv::Decoration::Binding:
+  case spirv::Decoration::DescriptorSet:
+  case spirv::Decoration::Location:
     if (auto intAttr = attr.second.dyn_cast<IntegerAttr>()) {
       args.push_back(intAttr.getValue().getZExtValue());
       break;
     }
     return emitError(loc, "expected integer attribute for ") << attrName;
   case spirv::Decoration::BuiltIn:
     if (auto strAttr = attr.second.dyn_cast<StringAttr>()) {
       auto enumVal = spirv::symbolizeBuiltIn(strAttr.getValue());
       if (enumVal) {
         args.push_back(static_cast<uint32_t>(enumVal.getValue()));
         break;
       }
       return emitError(loc, "invalid ")
              << attrName << " attribute " << strAttr.getValue();
     }
     return emitError(loc, "expected string attribute for ") << attrName;
+  case spirv::Decoration::Flat:
+  case spirv::Decoration::NoPerspective:
+    if (auto unitAttr = attr.second.dyn_cast<UnitAttr>()) {
+      // For unit attributes, the args list has no values so we do nothing
+      break;
+    }
+    return emitError(loc, "expected unit attribute for ") << attrName;
   default:
     return emitError(loc, "unhandled decoration ") << decorationName;
   }
   return emitDecoration(resultID, decoration.getValue(), args);
 }
 
 LogicalResult Serializer::processName(uint32_t resultID, StringRef name) {
   assert(!name.empty() && "unexpected empty string for OpName");

mlir/test/Dialect/SPIRV/Serialization/decorations.mlir

+// RUN: mlir-translate -split-input-file -test-spirv-roundtrip %s | FileCheck %s
+
+spv.module Logical GLSL450 requires #spv.vce<v1.0, [Shader], []> {
+  // CHECK: location = 0 : i32
+  spv.globalVariable @var1 {location = 0 : i32} : !spv.ptr<vector<4xf32>, Input>
+}
+
+// -----
+
+spv.module Logical GLSL450 requires #spv.vce<v1.0, [Shader], []> {
+  // CHECK: no_perspective
+  spv.globalVariable @var1 {no_perspective} : !spv.ptr<vector<4xf32>, Input>
+}
+
+// -----
+
+spv.module Logical GLSL450 requires #spv.vce<v1.0, [Shader], []> {
+  // CHECK: flat
+  spv.globalVariable @var2 {flat} : !spv.ptr<si32, Input>
+}
+