https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70053
Bug ID: 70053
Summary: Returning a struct of _Decimal128 values generates
extraneous stores and loads
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: bergner at gcc dot gnu.org
Target Milestone: ---
If we compile the following testcase, we see uneeded stores to the stack
followed by immediate loads from the same stack slots just before the return.
One set of stores/loads is completely unneeded and the others can be replaced
by simple fmrs.
bergner@genoa:~/gcc/BUGS/DFP/arith128-P8AT9/src$ cat t.i
typedef struct
{
_Decimal128 td0;
_Decimal128 td1;
} TDx2_t;
TDx2_t
D256_add_finite (_Decimal128 a, _Decimal128 b, _Decimal128 c)
{
TDx2_t result;
result.td0 = a;
result.td1 = b;
if (b == c)
{
result.td0 = c;
result.td1 = c;
return result;
}
return result;
}
bergner@genoa:~/gcc/BUGS/DFP/$
/home/bergner/gcc/build/gcc-fsf-mainline-base-debug/gcc/xgcc
-B/home/bergner/gcc/build/gcc-fsf-mainline-base-debug/gcc -O2 -mcpu=power8 -S
t.i
bergner@genoa:~/gcc/BUGS/DFP/$ cat t.s
.file "t.i"
.abiversion 2
.section ".text"
.align 2
.p2align 4,,15
.globl D256_add_finite
.type D256_add_finite, @function
D256_add_finite:
dcmpuq 7,4,6
beq 7,.L5
stfd 3,-64(1)
stfd 2,-56(1)
stfd 5,-48(1)
stfd 4,-40(1)
ori 2,2,0
lfd 3,-64(1)
lfd 2,-56(1)
lfd 5,-48(1)
lfd 4,-40(1)
blr
.p2align 4,,15
.L5:
stfd 7,-64(1)
stfd 6,-56(1)
stfd 7,-48(1)
stfd 6,-40(1)
ori 2,2,0
lfd 3,-64(1)
lfd 2,-56(1)
lfd 5,-48(1)
lfd 4,-40(1)
blr
