Add arith.constant support.

Handles scalar and vector.

Author: mshahneo

mlir/lib/Conversion/ArithToSPIRV/ArithToSPIRV.cpp

@@ -99,6 +99,14 @@ static FloatAttr convertFloatAttr(FloatAttr srcAttr, FloatType dstType,
   return builder.getF32FloatAttr(dstVal.convertToFloat());
 }
 
+// Get IntegerAttr from FloatAttr.
+IntegerAttr getIntegerAttrFromFloatAttr(FloatAttr floatAttr, Type dstType,
+                                        ConversionPatternRewriter &rewriter) {
+  APFloat floatVal = floatAttr.getValue();
+  APInt intVal = floatVal.bitcastToAPInt();
+  return rewriter.getIntegerAttr(dstType, intVal);
+}
+
 /// Returns true if the given `type` is a boolean scalar or vector type.
 static bool isBoolScalarOrVector(Type type) {
   assert(type && "Not a valid type");
@@ -296,8 +304,16 @@ struct ConstantCompositeOpPattern final
       SmallVector<Attribute, 8> elements;
       if (isa<FloatType>(srcElemType)) {
         for (FloatAttr srcAttr : dstElementsAttr.getValues<FloatAttr>()) {
-          FloatAttr dstAttr =
-              convertFloatAttr(srcAttr, cast<FloatType>(dstElemType), rewriter);
+          Attribute dstAttr = nullptr;
+          // Handle 8-bit float conversion to 8-bit integer.
+          if (srcElemType.getIntOrFloatBitWidth() == 8 &&
+              isa<IntegerType>(dstElemType)) {
+            dstAttr =
+                getIntegerAttrFromFloatAttr(srcAttr, dstElemType, rewriter);
+          } else {
+            dstAttr = convertFloatAttr(srcAttr, cast<FloatType>(dstElemType),
+                                       rewriter);
+          }
           if (!dstAttr)
             return failure();
           elements.push_back(dstAttr);
@@ -361,11 +377,17 @@ struct ConstantScalarOpPattern final
     // Floating-point types.
     if (isa<FloatType>(srcType)) {
       auto srcAttr = cast<FloatAttr>(cstAttr);
-      auto dstAttr = srcAttr;
+      Attribute dstAttr = srcAttr;
 
       // Floating-point types not supported in the target environment are all
       // converted to float type.
-      if (srcType != dstType) {
+      if (srcType.getIntOrFloatBitWidth() == 8 && isa<IntegerType>(dstType) &&
+          dstType.getIntOrFloatBitWidth() == 8) {
+        // If the source is an 8-bit float, convert it to a 8-bit integer.
+        dstAttr = getIntegerAttrFromFloatAttr(srcAttr, dstType, rewriter);
+        if (!dstAttr)
+          return failure();
+      } else if (srcType != dstType) {
         dstAttr = convertFloatAttr(srcAttr, cast<FloatType>(dstType), rewriter);
         if (!dstAttr)
           return failure();