https://bugs.llvm.org/show_bug.cgi?id=47625
Bug ID: 47625
Summary: Extra spilli/reload around function call
Product: libraries
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: enhancement
Priority: P
Component: Backend: X86
Assignee: unassignedb...@nondot.org
Reporter: david.bolvan...@gmail.com
CC: craig.top...@gmail.com, llvm-bugs@lists.llvm.org,
llvm-...@redking.me.uk, spatel+l...@rotateright.com
double a[8], b[8];
int x;
void __attribute__((noinline))
bar (void)
{
x = 1;
}
void __attribute__((noinline))
foo(int i)
{
double t1 = a[i];
bar ();
b[i] = 2*t1;
}
CLang -O3:
bar(): # @bar()
mov dword ptr [rip + x], 1
ret
foo(int): # @foo(int)
push rbx
sub rsp, 16
movsxd rbx, edi
movsd xmm0, qword ptr [8*rbx + a] # xmm0 = mem[0],zero
movsd qword ptr [rsp + 8], xmm0 # 8-byte Spill
call bar()
movsd xmm0, qword ptr [rsp + 8] # 8-byte Reload
addsd xmm0, xmm0
movsd qword ptr [8*rbx + b], xmm0
add rsp, 16
pop rbx
ret
GCC -O3:
bar():
mov DWORD PTR x[rip], 1
ret
foo(int):
movsx rdi, edi
movsd xmm0, QWORD PTR a[0+rdi*8]
call bar()
addsd xmm0, xmm0
movsd QWORD PTR b[0+rdi*8], xmm0
ret
https://godbolt.org/z/qKeEe8
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