Hi, Ian,
I have created a simpler example, just a function computing a sum of
its arguments:
int sum(int a, int b, int c, int d, int e, int f, int g, int h)
{
return a + b + c + d + e + f + g + h;
}
The "argp" is a pseudo-register included in all register classes, that
contain normal general-purpose regs. Here is the assembly output
(msp430-gcc -O0):
sum:
push r4
mov r1, argp
add #4, argp
sub #8, r1
mov r1, r4
/* prologue ends here (frame size = 8) */
.L__FrameSize_sum=0x8
.L__FrameOffset_sum=0xa
mov r15, @r4
mov r14, 2(r4)
mov r13, 4(r4)
mov r12, 6(r4)
mov @r4, r15
add 2(r4), r15
add 4(r4), r15
add 6(r4), r15
add @r16, r15
add 2(r16), r15
add 4(r16), r15
add 6(r16), r15
/* epilogue: frame size = 8 */
add #8, r1
pop r4
ret
.Lfe1:
.size sum,.Lfe1-sum
;; End of function
As you can see, argp does not get eliminated. During reload phase,
all pseudo-registers have reg_equiv_mem[i] and reg_equiv_address[i]
set to NULL, that prevents elimination from being executed.
Looks that some transformation before elimination has already
substituted "argp+offset" values into INSNs, preventing them from
being processed by elimination procedure. Here is a short example from
the test.c.172r.ira dump file (that should correspond to pre-reload
pass):
(insn 12 11 13 2 2.c:3 (set (reg:HI 15 r15 [orig:24 D.1206 ] [24])
(plus:HI (reg:HI 15 r15 [orig:25 D.1205 ] [25])
(mem/c/i:HI (reg/f:HI 16 argp) [0 e+0 S2 A16]))) 73 {*addhi3_3}
(nil))
Presently I am trying to compare RTL dumps from different passes with
ones produced by i386-gcc. It seems that in x86 the argp register gets
eliminated before the reload phase. However, on my msp430 port this
does not happen due to some reason.
Do you have any ideas, what other code can be responsible for
eliminating argp?
--
Best regards,
Ivan Shcherbakov mailto:shcherba...@eit.uni-kl.de
TU Kaiserslautern, Germany
Department of Real-Time Systems
