------- Additional Comments From dje at gcc dot gnu dot org 2005-07-27 22:03
-------
The testcase passes three structs with three members each for a total of nine
words. AIX, Darwin, and PPC64 Linux pass structs by value in GPRs r3-r10
allowing a maximum of 8 words. The ninth argument is passed on the stack. This
bug appears to be a problem with either argument passing or scheduling.
struct S a = { 3, 4, 5 }, b = { 6, 7, 8 }, c = { 9, 10, 11 };
main() calls baz3 (c, a, b) and the arguments are correct
9, 10, 11, 3, 4, 5, 6, 7 in GPRs and 8 on stack at 56(r1)
baz3 (struct S x, struct S y, struct S z)
{
return foo3 (y, z, x);
}
is compiled as:
addi r2,r1,24
addi r11,r1,36
stswi r3,r2,12 <== store baz3 argument x to r1+24,28,32
addi r2,r1,48 <== address of foo3 second argument
stswi r6,r11,12
lwz r0,32(r1) <== load x.c
stw r9,48(r1)
mr r9,r3
stw r10,52(r1)
stw r0,56(r1) <== store x.c to third argument last member on stack
lwz r10,28(r1)
lswi r3,r11,12
lswi r6,r2,12 <== load foo3 second argument from r2+48,52,56
b _foo3
GCC stores the argument passed on the stack for foo3 before loading the second
argument from the same location.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23090
