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ARM mode Thumb mode switching

Dave Mathew
Note: This was originally posted on 13th January 2011 at http://forums.arm.com

Hi,

Let me explain my problem,
i come across one situation

cmp r1,#0
beq labels_of1

i would like to merge both the instructions in to one. for that i would like to use cbz (thumb instruction)

but my compiler shows an error message that this particular instruction not present in the Instruction.

Since the instruction is cbz the compilation should be in thum mode. how can i modify my make file and how can i switch the mode from ARM to thumb for execute the optimized instruction.

please let me know the mode change needs any extra cycle.


Rgds
Dave
Parents
  • Note: This was originally posted on 19th January 2011 at http://forums.arm.com


      SUB  r3,r0,r1
      SUB  r4,r1,r2
      ADDS    r3,r3,#(25-1)
      ADDS    r4,r4,#(30-1) 
      CMP  r3,#(2*(25-1))
      SUB  r3,r2,r0
      CMPLS   r4,#(2*(30-1))
      ADD  r3,r3,#(45-1)
      BHI  Take_None   // modify none
      CMP  r3,#(2*(45-1))
      BHI  Take_Second // modify a0,b0
      B    Take_First  // modify a0,b0,c0


    Hum. Yes that's nice !
    Great ;)

    Why do you used ADDS ??? ADD is enough no?

    Etienne

Reply
  • Note: This was originally posted on 19th January 2011 at http://forums.arm.com


      SUB  r3,r0,r1
      SUB  r4,r1,r2
      ADDS    r3,r3,#(25-1)
      ADDS    r4,r4,#(30-1) 
      CMP  r3,#(2*(25-1))
      SUB  r3,r2,r0
      CMPLS   r4,#(2*(30-1))
      ADD  r3,r3,#(45-1)
      BHI  Take_None   // modify none
      CMP  r3,#(2*(45-1))
      BHI  Take_Second // modify a0,b0
      B    Take_First  // modify a0,b0,c0


    Hum. Yes that's nice !
    Great ;)

    Why do you used ADDS ??? ADD is enough no?

    Etienne

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