https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95792
Bug ID: 95792
Summary: Failure to optimize assignment of struct members to
memset
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: gabravier at gmail dot com
Target Milestone: ---
#define F0(a) i##a,
#define F1(a) F0(a##0) F0(a##1) F0(a##2) F0(a##3) F0(a##4) F0(a##5) F0(a##6)
F0(a##7)
#define F2(a) F1(a##0) F1(a##1) F1(a##2) F1(a##3) F1(a##4) F1(a##5) F1(a##6)
F1(a##7)
#define F3(a) F2(a##0) F2(a##1) F2(a##2) F2(a##3) F2(a##4) F2(a##5) F2(a##6)
F2(a##7)
#define F4(a) F3(a##0) F3(a##1) F3(a##2) F3(a##3) F3(a##4) F3(a##5) F3(a##6)
F3(a##7)
#define H0(a) s->i##a = 0;
#define H1(a) H0(a##0) H0(a##1) H0(a##2) H0(a##3) H0(a##4) H0(a##5) H0(a##6)
H0(a##7)
#define H2(a) H1(a##0) H1(a##1) H1(a##2) H1(a##3) H1(a##4) H1(a##5) H1(a##6)
H1(a##7)
#define H3(a) H2(a##0) H2(a##1) H2(a##2) H2(a##3) H2(a##4) H2(a##5) H2(a##6)
H2(a##7)
#define H4(a) H3(a##0) H3(a##1) H3(a##2) H3(a##3) H3(a##4) H3(a##5) H3(a##6)
H3(a##7)
struct foo {
int
F4(0)
bar;
};
void f (struct foo *s)
{
H4(0)
}
With -O3, GCC "optimizes" this by storing words containing 0 for the entire
struct. LLVM instead just calls memset, which looks more reasonable.
