JAL Computing
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Sample IL Program in AssemblerHere is some fun with bit level code that takes an int32 and outputs the bit value by left shifting the binary representation of the integer 32 times. This code demonstrates the use of try catch IL and the use of local variables to store temporary values. The CLR (Common Language Runtime) will complain if the try catch logic can lead to invalid states. We initialize the local variable n_input before we try to assign it a user value in try. This makes the CLR happy! // TestILAssembler.il
// 11.28.04 Jeff Louie
.assembly extern mscorlib {}
.assembly TestILAssembler {.ver 1:0:1:0}
.method private static void Main(string[] args) cil managed
{
.entrypoint
.custom instance void [mscorlib]System.STAThreadAttribute::.ctor() =
( 01 00 00 00 )
.maxstack 4
.locals init ([0] int32 n_counter,[1] int32 n_input)
.try // get user input
{
ldstr "Enter number: "
call void [mscorlib]System.Console::Write(string)
call string [mscorlib]System.Console::ReadLine()
call int32 [mscorlib]System.Int32::Parse(string)
// parse may throw exception
stloc.1 // place valid user input into n_input
leave.s got_value // leave don't branch from try
} // end .try
catch [mscorlib]System.Object
{
pop // remove exception from stack
ldstr "Invalid Number."
call void [mscorlib]System.Console::WriteLine(string)
leave exit // invalid input so exit program
} // end handler
got_value: ldloc.1 // push value n_input onto stack dup call void [mscorlib]System.Console::Write(int32) ldstr " [Input value] " call void [mscorlib]System.Console::WriteLine(string) // **** (for int i=0; i<32; i++) **** load_counter: ldc.i4 0 // initialize n_counter 0 stloc.0 // store in local variable n_count begin_loop: ldloc.0 // get current counter value ldc.i4 32 bge end_loop // break loop if counter is >=32 dup ldc.i4 0x80000000 // bit mask 10000000000000000000000000000000 and // clear all bits except most significant ldc.i4 0x80000000 ceq // push 1 if most sig bit is true, else 0 call void [mscorlib]System.Console::Write(int32) ldc.i4 1 // push 1 shl // *** shift left 1, zero least sig bit **** ldloc.0 // get n_counter ldc.i4 1 add // add 1 to n_counter, postfix increment stloc.0 // store new n_counter value br begin_loop // branch to loop again // **** end for loop **** end_loop: pop // remove input value should be all zeros ldstr " [32 bit value] " end_algo: call void [mscorlib]System.Console::WriteLine(string) exit: ldstr "JAL 11.25.04" call void [mscorlib]System.Console::WriteLine(string) ret } // end of method Main Here is the output [input]: Enter number: 10 Pretty cool! |
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