[fpc-devel] sse2 registers

[Vincent Snijders]

I am trying out the sse2 support in fpc 2.1.1 and compile my code with 
-Cfsse2.

The program is the mandelbrot benchmark:
http://shootout.alioth.debian.org/gp4/benchmark.php?test=mandelbrot&lang=fpascal

The innerloop is like this:
       Zr := 0;  Zi := 0; Tr := 0; Ti := 0;
       i := 0;
       while (i<50) and (Tr + Ti< limit) do begin
         inc(i);
         Zi := 2*Zr*Zi + Ci;
         Zr := Tr - Ti + Cr;
         Ti := Zi * Zi;
         Tr := Zr * Zr;
       end;

If I look at the generated assembler, I noticed that only %xmm0 is used 
and all each time the variable needs to be retrieved from the stack.

# Var Zr located in register mreg0md
# Var Zi located in register mreg0md
# Var Ti located in register mreg0md
# Var Tr located in register mreg0md
# Var Cr located in register mreg0md
# Var Ci located in register mreg0md

...

# [33] Zr := Tr - Ti + Cr;
	movsd	-88(%ebp),%xmm0
	subsd	-80(%ebp),%xmm0
	addsd	-96(%ebp),%xmm0
	movsd	%xmm0,-112(%ebp)
# [34] Ti := Zi * Zi;
	movsd	-72(%ebp),%xmm0
	mulsd	-72(%ebp),%xmm0
	movsd	%xmm0,-80(%ebp)

I thought there were more than one xmm registers. Why aren't they used?

Vincent