[mlir][llvm] Fix verifier for const int and dense (#74340)

Continuation of #74247 to fix
#56962. Fixes verifier for
(Integer Attr):
```mlir
llvm.mlir.constant(1 : index) : f32
```
and (Dense Attr):
```mlir
llvm.mlir.constant(dense<100.0> : vector<1xf64>) : f32
```

## Integer Attr

The addition that this PR makes to `LLVM::ConstantOp::verify` is meant
to be exactly verifying the code in
`mlir::LLVM::detail::getLLVMConstant`:


https://github.com/llvm/llvm-project/blob/9f78edbd20ed922cced9482f7791deb9899a6d82/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp#L350-L353

One failure mode is when the `type` (`llvm.mlir.constant(<value>) :
<type>`) is not an `Integer`, because then the `cast` in
`getIntegerBitWidth` will crash:


https://github.com/llvm/llvm-project/blob/dca432cb7b1c282f5dc861095813c4f40f109619/llvm/include/llvm/IR/DerivedTypes.h#L97-L99

So that's now caught in the verifier.

Apart from that, I don't see anything we could check for. `sextOrTrunc`
means "Sign extend or truncate to width" and that one is quite
permissive. For example, the following doesn't have to be caught in the
verifier as it doesn't crash during `mlir-translate -mlir-to-llvmir`:

```mlir
llvm.func @main() -> f32 {
  %cst = llvm.mlir.constant(100 : i64) : f32
  llvm.return %cst : f32
}
```

## Dense Attr

Crash if not either a MLIR Vector type or one of these:


https://github.com/llvm/llvm-project/blob/9f78edbd20ed922cced9482f7791deb9899a6d82/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp#L375-L391

Author: rikhuijzer

mlir/lib/Dialect/LLVMIR/IR/LLVMDialect.cpp

@@ -2544,6 +2544,10 @@ LogicalResult LLVM::ConstantOp::verify() {
   if (!llvm::isa<IntegerAttr, ArrayAttr, FloatAttr, ElementsAttr>(getValue()))
     return emitOpError()
            << "only supports integer, float, string or elements attributes";
+  if (auto intAttr = dyn_cast<IntegerAttr>(getValue())) {
+    if (!llvm::isa<IntegerType>(getType()))
+      return emitOpError() << "expected integer type";
+  }
   if (auto floatAttr = dyn_cast<FloatAttr>(getValue())) {
     const llvm::fltSemantics &sem = floatAttr.getValue().getSemantics();
     unsigned floatWidth = APFloat::getSizeInBits(sem);
@@ -2558,6 +2562,12 @@ LogicalResult LLVM::ConstantOp::verify() {
       return emitOpError() << "expected integer type of width " << floatWidth;
     }
   }
+  if (auto splatAttr = dyn_cast<SplatElementsAttr>(getValue())) {
+    if (!getType().isa<VectorType>() && !getType().isa<LLVM::LLVMArrayType>() &&
+        !getType().isa<LLVM::LLVMFixedVectorType>() &&
+        !getType().isa<LLVM::LLVMScalableVectorType>())
+      return emitOpError() << "expected vector or array type";
+  }
   return success();
 }
 

mlir/test/Target/LLVMIR/llvmir-invalid.mlir

@@ -7,6 +7,14 @@ func.func @foo() {
 
 // -----
 
+llvm.func @vector_with_non_vector_type() -> f32 {
+  // expected-error @below{{expected vector or array type}}
+  %cst = llvm.mlir.constant(dense<100.0> : vector<1xf64>) : f32
+  llvm.return %cst : f32
+}
+
+// -----
+
 llvm.func @no_non_complex_struct() -> !llvm.array<2 x array<2 x array<2 x struct<(i32)>>>> {
   // expected-error @below{{expected struct type to be a complex number}}
   %0 = llvm.mlir.constant(dense<[[[1, 2], [3, 4]], [[42, 43], [44, 45]]]> : tensor<2x2x2xi32>) : !llvm.array<2 x array<2 x array<2 x struct<(i32)>>>>
@@ -31,6 +39,14 @@ llvm.func @struct_wrong_attribute_element_type() -> !llvm.struct<(f64, f64)> {
 
 // -----
 
+llvm.func @integer_with_float_type() -> f32 {
+  // expected-error @+1 {{expected integer type}}
+  %0 = llvm.mlir.constant(1 : index) : f32
+  llvm.return %0 : f32
+}
+
+// -----
+
 llvm.func @incompatible_float_attribute_type() -> f32 {
   // expected-error @below{{expected float type of width 64}}
   %cst = llvm.mlir.constant(1.0 : f64) : f32