[Flang] Add type conversion for FIR integer kind

[kiranchandramohan]

Summary

Convert fir.int<kind> to their llvm equivalent type

This patch is part of the upstreaming effort from fir-dev branch.

Co-authored-by: Eric Schweitz <[e-mail]>

[awarzynski]

LGTM

[clementval]

LG

flang/lib/Optimizer/CodeGen/TypeConverter.h

LLVMTypeConverter(mlir::ModuleOp module)
     addConversion([&](BoxType box) { return convertBoxType(box); });
     addConversion([&](BoxCharType boxchar) {
       LLVM_DEBUG(llvm::dbgs() << "type convert: " << boxchar << '\n');
       return convertType(specifics->boxcharMemoryType(boxchar.getEleTy()));
     });
     addConversion(
         [&](fir::CharacterType charTy) { return convertCharType(charTy); });
     addConversion([&](HeapType heap) { return convertPointerLike(heap); });
+    addConversion([&](fir::IntegerType intTy) {
+      return mlir::IntegerType::get(
+          &getContext(), kindMapping.getIntegerBitsize(intTy.getFKind()));
+    });
     addConversion([&](fir::LogicalType boolTy) {
       return mlir::IntegerType::get(
           &getContext(), kindMapping.getLogicalBitsize(boolTy.getFKind()));
     });
     addConversion(
         [&](fir::PointerType pointer) { return convertPointerLike(pointer); });
     addConversion(
         [&](fir::RecordType derived) { return convertRecordType(derived); });

flang/test/Fir/types-to-llvm.fir

 // CHECK-SAME: !llvm.ptr<struct<"ZT", ()>>
 
 func private @foo8(%arg0: !fir.heap<!fir.type<_QMalloc_assignTt{i:i32}>>)
 // CHECK-LABEL: foo8
 // CHECK-SAME: !llvm.ptr<struct<"_QMalloc_assignTt", (i32)>>
 
 // -----
 
+// Test `!fir.integer<KIND>` conversion.
+
+func private @foo0(%arg0: !fir.int<1>)
+// CHECK-LABEL: foo0
+// CHECK-SAME: i8
+
+func private @foo1(%arg0: !fir.int<2>)
+// CHECK-LABEL: foo1
+// CHECK-SAME: i16
+
+func private @foo2(%arg0: !fir.int<4>)
+// CHECK-LABEL: foo2
+// CHECK-SAME: i32
+
+func private @foo3(%arg0: !fir.int<8>)
+// CHECK-LABEL: foo3
+// CHECK-SAME: i64
+
+func private @foo4(%arg0: !fir.int<16>)
+// CHECK-LABEL: foo4
+// CHECK-SAME: i128
+
+// -----
+
 // Test `!fir.logical<KIND>` conversion.
 
 func private @foo0(%arg0: !fir.logical<1>)
 // CHECK-LABEL: foo0
 // CHECK-SAME: i8
 
 func private @foo1(%arg0: !fir.logical<2>)
 // CHECK-LABEL: foo1