https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91633
Bug ID: 91633
Summary: Why -funroll-loops affect code without loop.
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: crazylht at gmail dot com
CC: hjl.tools at gmail dot com, skpgkp2 at gmail dot com
Target Milestone: ---
Target: i386, x86-64
This testcase is cut from 538.exchange_r in SPEC2017.
---
typedef struct pixel{
float red;
float green;
float blue;
}pixel;
typedef struct pixel2{
unsigned short red;
unsigned short green;
unsigned short blue;
}pixel2;
extern double* p;
int foo (pixel* a, pixel2* b)
{
double ret = (a->red-b->red) * (a->red-b->red)
+ (a->green-b->green) * (a->green-b->green)
+ (a->blue-b->blue) * (a->blue-b->blue);
if (ret <= *p)
return 1;
return 0;
}
---
It is supposed -funroll-loops wouldn't affect code generation, but currently
it's not, refer to https://godbolt.org/z/6hvQC7.
What i got in function process_options in toplev.c:
----
if (flag_rename_registers == AUTODETECT_VALUE)
flag_rename_registers = flag_unroll_loops;
----
Also note pass rnreg will affect sched2.
