[mlir][llvm] Mark additional ops as pure.

[gysit]

Summary

The revision marks the overflow arithmetic intrinsics
and the freeze operation as pure. This change enables
inlining and possible other optimizations for these
operations.

[Dinistro]

LGTM!

mlir/include/mlir/Dialect/LLVMIR/LLVMIntrinsicOps.td

string mlirBuilder = [{
     $_op = $_builder.create<LLVM::LifetimeEndOp>(
       $_location, $_int_attr($size), $ptr);
   }];
 }
 
 // Intrinsics with multiple returns.
 
 class LLVM_ArithWithOverflowOp<string mnem>
-    : LLVM_IntrOp<mnem, [0], [], [SameOperandsElementType], 2>,
+    : LLVM_IntrOp<mnem, [0], [], [Pure, SameOperandsElementType], 2>,
       Arguments<(ins LLVM_ScalarOrVectorOf<AnySignlessInteger>,
                  LLVM_ScalarOrVectorOf<AnySignlessInteger>)>;
 
 def LLVM_SAddWithOverflowOp : LLVM_ArithWithOverflowOp<"sadd.with.overflow">;
 def LLVM_UAddWithOverflowOp : LLVM_ArithWithOverflowOp<"uadd.with.overflow">;
 def LLVM_SSubWithOverflowOp : LLVM_ArithWithOverflowOp<"ssub.with.overflow">;
 def LLVM_USubWithOverflowOp : LLVM_ArithWithOverflowOp<"usub.with.overflow">;
 def LLVM_SMulWithOverflowOp : LLVM_ArithWithOverflowOp<"smul.with.overflow">;

mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td

def LLVM_SelectOp
   string llvmInstName = "Select";
   string mlirBuilder = [{
     auto op = $_builder.create<LLVM::SelectOp>(
       $_location, $_resultType, $condition, $trueValue, $falseValue);
     moduleImport.setFastmathFlagsAttr(inst, op);
     $res = op;
   }];
 }
-def LLVM_FreezeOp : LLVM_Op<"freeze", [SameOperandsAndResultType]> {
+def LLVM_FreezeOp : LLVM_Op<"freeze", [Pure, SameOperandsAndResultType]> {
   let arguments = (ins LLVM_Type:$val);
   let results = (outs LLVM_Type:$res);
   let builders = [LLVM_OneResultOpBuilder];
   let assemblyFormat = "$val attr-dict `:` type($val)";
   string llvmInstName = "Freeze";
   string llvmBuilder = "$res = builder.CreateFreeze($val);";
   string mlirBuilder = [{
     $res = $_builder.create<LLVM::FreezeOp>($_location, $val);