Summary:
Failure to update the FP / vector state was causing daemon(3) to violate C ABI by failing to preserve nonvolatile registers.
This was causing a weird issue where moused was not working on PowerBook G4s when daemonizing, but was working fine when running it foreground.
Force saving off the same state that cpu_switch() does in cases where we are about to copy a thread.
MFC after: 1 week
Sponsored by: Tag1 Consulting, Inc.
Test Plan:
```
/*
* Test for ABI violation due to side effects of daemon(3).
*
* NOTE: Compile with -O2 to see the effect.
*/
/* Allow compiling for Linux too. */
static double test = 1234.56f;
/*
* This contrivance coerces clang to not bounce the double
* off of memory again in main.
*/
void __attribute__((noinline))
print_double(int j1, int j2, double d)
{
printf("%f\n", d);
}
int
main(int argc, char *argv[])
{
print_double(0, 0, test);
if (daemon(0, 1)) {
}
/* Compiler assumes nonvolatile regs are intact... */
print_double(0, 0, test);
return(0);
}
```
Working output:
```
1234.560059
1234.560059
```
Output in broken case:
```
1234.560059
0.0
```
Reviewers: #powerpc
Subscribers: jhibbits, luporl, alfredo
Tags: #powerpc
Differential Revision: https://reviews.freebsd.org/D29851
35a1aa5f9c