https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70465
Bug ID: 70465
Summary: Poor code for x87 asm
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: law at redhat dot com
Target Milestone: ---
Compile with -O2 -fomit-frame-pointer -m32:
double
atan2 (double y, double x)
{
double res = 0.0;
asm ("fpatan"
: "=t" (res) : "u" (y), "0" (x) : "st(1)");
return res;
}
There's an unnecessary fxch insn. According to Jakub, it started somewhere
between r139525 and r139600. ie, gcc-4.3 got good code, gcc-4.4 has the
unwanted fxch
I briefly looked at the dumps, things seemed OK coming out of the register
allocator, but then reg-stack mucks things up.
