https://gcc.gnu.org/bugzilla/show_bug.cgi?id=128423
Bug ID: 128423
Summary: Missed simplification/reassociation for RISC-V
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: law at gcc dot gnu.org
Target Milestone: ---
Compile with -O2 -march=rv64gcbv:
typedef unsigned long uintptr_t;
int f(char *d, char *m, char *b)
{
return ((uintptr_t)d - (uintptr_t)b - 2 > 4) & ((uintptr_t)d - (uintptr_t)m -
2 > 4);
}
int g(char *d, char *m, char *b, int *x)
{
if (((uintptr_t)d - (uintptr_t)b - 2 > 4) & ((uintptr_t)d - (uintptr_t)m - 2
> 4))
return x[0];
return x[1];
}
In both cases we can improve by reassociating and doing the subtraction just
once. Something like this:
Before, f:
sub a1,a0,a1
sub a0,a0,a2
addi t1,a0,-2
addi t0,a1,-2
minu t2,t1,t0
sltiu a2,t2,5
xori a0,a2,1
ret
After, f:
addi t0,a0,-2
sub a1,t0,a1
sub a2,t0,a2
minu a1,a1,a2
sltiu a1,a1,5
xori a0,a1,1
ret
