RomRaider

Hi i'm new to disassemble, someone can explain which is correct for the below SH4B instruction?

let assume R0=H'A

shll R0 ; R0 should shift left one bit, so it is H'A0 or H'B?

another question,

mov.w @R13, R6
cmp/gt R6,R14 ;if R6<R14, so T=0
bt loc_2D9A0
mov R6,R14
bra loc_2d976

since T=0 so need skip the bt loc_2D9A0, do we need execute mov R6,R14 or skip bt and mov all together?

It would be H'14

This is correctly stated as:
cmp/gt R6,R14 ;When signed and R14 > R6, T=1
(don't forget the condition when they are equal)
The move instruction would be skipped if T=1 as the BT instruction is not a BT/S instruction.

You'd be best to read the software manual, assuming this is a SH705x processor your are working with.
http://documentation.renesas.com/doc/pr ... h_2esm.pdf

thanks for the explanation. read that manual many times just can't understand with just one example

finally understand how is pull2d routine work. pull3d is much more complicated

how is the stack pointer R15 refer in below code?

fmov.s fr3,@(r0,r15)

r0 would be 8, but what is r15 refer to?

pull3D is just pull2D executed twice, once time against each axis. The result of the two intercept points in then blended together.
There is more that one pull2D and pull3D. There are quite a few of them depending on the data type table being pulled from. I know there's separate routines for tables with and without scaling entries, float, byte and word data.
There's also references to the data types in the pull routines, int8, unit8, int16, unit16 etc...

r15 is the stack pointer, so you will never know its true value. As code is executed the stack pointer changes with every call and interrupt. All you need to know is r15 is an address in RAM and all references to r15 is a reference to some address X (btw: at boot r15 is set to the 4-byte value stored at ROM address 0x04). So the statements:
mov.l r14, @-r15 means decrement r15 by 4 bytes then put the current value of r14 on the stack where r15 points.

For your example with r0 == 8;
fmov.s fr3,@(r0,r15) means, at the location pointed to by (r15+8) put the value of fr3. The value of r15 does not change.

You'll have to make your own map of where r15 points to in each routine. So if this routine calls another routine before this one is finished then r15 will change in the called routine and have a different map than the current routine.
More info is in the software manual section 5.2 Addressing Modes (Indirect indexed register addressing).