------- Comment #3 from rbala at coresfoundation dot com 2009-02-15 20:43
-------
Hi all,
Correct me if I'm wrong.
@mp2 - newlib is a source of 'C' libraries for various arch's. You won't find a
directory as such called newlib. While building your toolchain, you compile all
the files in the newlib source.
Coming to your issue, I shall verify it again. I don't think it is a GCC
issue., but I shall verify it. I saw the assembly code, but I shall again
generate the assembly myself., atleast from my perspective, I would generate
the assembly by using a local function name rather than using main().
I mean I wouldn't use the fn.name as main() when I was to debug a function's
assembly, because main() being a generic fn. Name might induce some other
fn.calls(I may be wrong here) but what I'm saying is, its just a good practice.
>From what I'm seeing, I don't know if it might be a typecasting issue, (don't
know for sure), did you try something like this? " (float)out =
sqrt((float)in); "
(In reply to comment #2)
> (In reply to comment #1)
> > sqrt is usually implemented as a library function and GCC does not
> > implement it
> > for you. Do you use newlib?
>
> My previous reply doesn't seem to have made it into the system. Here it is
> again...
> As far as I can see, there is no library named newlib or anything near it on
> this system. What is this library and where do I get it?
>
> I am not convinced that this is a library issue as two of the sqrt() functions
> in the program work though the last has been pre-evaluated to a constant by
> the
> gcc compiler. The problem only happens when the result is stored in a
> variable.
>
> I cannot find any good documentation for the Arm9 assembler but by inspired
> guesswork interpreting the instruction names, the code generated for the
> program looks very odd as there appears to be a conditional jump around the
> sqrt() function.
>
> int main()
> {
> double in, out;
> in = 2.0;
> out = sqrt(in);
> printf("%f\n", out);
> printf("%f\n", sqrt(in));
> printf("%f\n", sqrt(2.0));
> return 0;
> }
>
> Assembler code...
>
> .file "a.c"
> .section .rodata
> .align 2
> .LC0:
> .ascii "%f\012\000"
> .text
> .align 2
> .global main
> .type main, %function
> main:
> @ args = 0, pretend = 0, frame = 24
> @ frame_needed = 1, uses_anonymous_args = 0
> mov ip, sp
> stmfd sp!, {r4, fp, ip, lr, pc}
> sub fp, ip, #4
> sub sp, sp, #24
> adr r3, .L4
> ldmia r3, {r3-r4}
> str r3, [fp, #-32]
> str r4, [fp, #-28]
> ldfd f0, [fp, #-32]
> sqtd f0, f0
> stfd f0, [fp, #-40]
> ldfd f0, [fp, #-40]
> ldfd f0, [fp, #-40]
> cmf f0, f0
> beq .L2 <============
> sub r0, fp, #32
> ldmia r0, {r0-r1}
> bl sqrt
> stfd f0, [fp, #-40]
> .L2:
> sub r3, fp, #40
> ldmia r3, {r3-r4}
> str r3, [fp, #-24]
> str r4, [fp, #-20]
> ldr r0, .L4+16
> sub r1, fp, #24
> ldmia r1, {r1-r2}
> bl printf
> sub r0, fp, #32
> ldmia r0, {r0-r1}
> bl sqrt
> stfd f0, [sp, #-8]!
> ldmfd sp!, {r3, r4}
> ldr r0, .L4+16
> mov r1, r3
> mov r2, r4
> bl printf
> ldr r0, .L4+16
> adr r1, .L4+8
> ldmia r1, {r1-r2}
> bl printf
> mov r3, #0
> mov r0, r3
> sub sp, fp, #16
> ldmfd sp, {r4, fp, sp, pc}
> .L5:
> .align 2
> .L4:
> .word 1073741824
> .word 0
> .word 1073127582
> .word 1719614413
> .word .LC0
> .size main, .-main
> .ident "GCC: (GNU) 4.1.2 20061115 (prerelease) (Debian 4.1.1-21)"
>
>
> Martin Phillips
> Ladybridge Systems Ltd
> 17b Coldstream Lane, Hardingstone, Northampton, NN4 6DB
> +44-(0)1604-709200
>
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39085
