[mlir] Mark CastOp class's shape constraint

[jpienaar]

Summary

These ops have the same operands and result shapes.

[jpienaar]

Rebase and fix new test that would fail due to different order of error checking now.

[ftynse]

Cool, better error messages!

mlir/include/mlir/Dialect/StandardOps/IR/Ops.td

class Std_Op<string mnemonic, list<OpTrait> traits = []> :
   let printer = [{ return ::print(p, *this); }];
   let verifier = [{ return ::verify(*this); }];
   let parser = [{ return ::parse$cppClass(parser, result); }];
 }
 
 // Base class for standard cast operations. Requires single operand and result,
 // but does not constrain them to specific types.
 class CastOp<string mnemonic, list<OpTrait> traits = []> :
-    Std_Op<mnemonic, !listconcat(traits, [NoSideEffect])> {
+    Std_Op<mnemonic,
+           !listconcat(traits, [NoSideEffect, SameOperandsAndResultShape])> {
 
   let results = (outs AnyType);
 
   let builders = [OpBuilder<
     "OpBuilder &builder, OperationState &result, Value source, Type destType", [{
        impl::buildCastOp(builder, result, source, destType);
   }]>];
 

mlir/test/IR/invalid-ops.mlir

func @fpext_f32_to_i32(%arg0 : f32) {
   // expected-error@+1 {{are cast incompatible}}
   %0 = fpext %arg0 : f32 to i32
   return
 }
 
 // -----
 
 func @fpext_vec(%arg0 : vector<2xf16>) {
-  // expected-error@+1 {{are cast incompatible}}
+  // expected-error@+1 {{requires the same shape for all operands and results}}
   %0 = fpext %arg0 : vector<2xf16> to vector<3xf32>
   return
 }
 
 // -----
 
 func @fpext_vec_f32_to_f16(%arg0 : vector<2xf32>) {
   // expected-error@+1 {{are cast incompatible}}
func @fptrunc_f32_to_i32(%arg0 : f32) {
   // expected-error@+1 {{are cast incompatible}}
   %0 = fptrunc %arg0 : f32 to i32
   return
 }
 
 // -----
 
 func @fptrunc_vec(%arg0 : vector<2xf16>) {
-  // expected-error@+1 {{are cast incompatible}}
+  // expected-error@+1 {{requires the same shape for all operands and results}}
   %0 = fptrunc %arg0 : vector<2xf16> to vector<3xf32>
   return
 }
 
 // -----
 
 func @fptrunc_vec_f16_to_f32(%arg0 : vector<2xf16>) {
   // expected-error@+1 {{are cast incompatible}}