hi
example code:
function roo(lk:longint):byte;
var k : longint;
bit : longint;
num : byte;
begin
num:=0;
for k:=0 to 25 do
begin
bit:= longint(1) shl k;
if (lk and bit) 0 then
begin
lk:=lk xor bit;
inc(num);
end;
end;
roo:=num;
end;
begin
end.asm code
# [109] bit:= longint(1) shl k;
movslq %ecx,%rdx
# Register r8d allocated
movl $1,%r8d
# Register edx,edx allocated
shlx %edx,%r8d,%edx
# Register r8d released
# Register edx allocated
movl %edx,%esi
# Peephole Optimization: %esi = %edx; changed to minimise pipeline stall (MovXXX2MovXXX) # Peephole Optimization: Mov2Nop 4 done
what purpose serve: movslq %ecx,%rdx ?
movl %edx,%esi seems unnecessary,
when just enough would be
movl $1,%esi
shlx %ecx,%esi,%esi