p.s. tested execution speed and there is no measurable difference.
> 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
> #
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);
- Reply to message -
Subject: Re: [fpc-devel] generate assembler with no clear purpose MOV
Date: otrd., 4 febr. 2020, 22:24
From: J. Gareth Moreton
To:
> To hazard a guess, it's sign-extending to the CPU word size as an
> intermediate step. It's not something the peephole optimizer
Are you able to dump the nodes as well with -an? (You'll need to define
-dEXTDEBUG though) That might give some clues behind the presence of
that movslq instruction.
Gareth aka. Kit
On 04/02/2020 21:15, Marģers . via fpc-devel wrote:
- Reply to message -
Subject: Re: [fpc-devel]
test plz ignore
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From: J. Gareth Moreton
To:
> Are you able to dump the nodes as well with -an? (You'll need to define
> -dEXTDEBUG though) That might give some clues behind the presence of
> that movslq instruction.
building compiler with -dEXTDEBUG does not work for me
make singlezipinstall
Hi everyone,
I have an idea in regards to improving compilation speed. It mostly applies to
the x86 family, but I see no
reason why it cannot be platform-agnostic. The idea is basically this:
- The optimisation level selected (-O1, -O2, -O3/-O4) dictates the MAXIMUM
number of times Pass 1
