ARMv7-M assembly ITEE usage

• Problem:

I'm trying to get the ITEE EQ ie 'If-Then-Else-Else Equal' block to work when R6==0, with THEN branching into the END label but the assembler called out an error on the line: BEQ END

• Program info:

I'm doing a program that is in pertinence with Optimization. I'm using a Gradient Descent to converge to the point where gradient is 0 to find the solution x* that minimises some function f(x). I'm using C language to call an assembly function which is this program here.

Here is my program where the error is:

        CMP R6, #0          @ Compare f'(x) with 0
        ITEE EQ             @ If R6 == 0, Then-Else-Else
        BEQ END             @ Calls END label if equal
        SUBNE R0, R6        @ Change R0(x) in the opp direction of gradient to get lower value of f(x) if not equal
        BNE optimize        @ Branch to optimize if not equal

This is my first assembly program using the NXP LPC1769 for a school assignment. Do let me know what I'm missing or I have done wrong. Thank you!

Here is my whole program:

.syntax unified
.cpu cortex-m3
.thumb
.align 2
.global optimize
.thumb_func

optimize:
@  Write optimization function in assembly language here

        MOV R5, INLAMBDA    @ R5 holds value of inverse lambda(10) ie to eliminate floating point
        LDR R6, #2          @ Load R6 with value '2' ie constant of f'(x)
        MUL R6, R1, R6      @ Multiply R6(2) with R1(a) & store to R6(results)
        MLA R6, R6, R0, R2  @ Multiply R6(results) with R0(x) & sum with R2(b) to get f'(x). Store & update results to R6
        SDIV R6, R5         @ Divide R6(results) by R5(1/lambda) to get f'(x) * lambda

        CMP R6, #0          @ Compare f'(x) with 0
        ITEE EQ             @ If R6 == 0, Then-Else-Else
        BEQ END             @ Calls END label if equal
        SUBNE R0, R6        @ Change R0(x) in the opp direction of gradient to get lower value of f(x) if not equal
        BNE optimize        @ Branch to optimize if not equal

@  End label
END:

BX LR

@ Define constant values
CONST: .word 123
INLAMBDA: .word 10      @ Inverse lambda 1 / lambda(0.1) is 10