Hi,
I am running into trouble with a volatile memory move on my port of
GCC4.4.4. The code is:
int main(void)
{
register volatile float sc = 1E35;
if(sc < 1.000050000e35)
return 1;
return 0;
}
The very first part of this code is being expanded as:
;; sc ={v} 1.0000000409184787596297531937521664e+35;
(insn 5 4 6 vol.c:3 (set (reg/f:QI 20)
(symbol_ref/u:QI ("*?LC0") [flags 0x2])) -1 (nil))
(insn 6 5 7 vol.c:3 (set (reg:QI 1 AL)
(mem/u/c/i:QI (plus:QI (reg/f:QI 20)
(const_int 1 [0x1])) [2 S1 A16])) -1 (nil))
(insn 7 6 8 vol.c:3 (set (reg:QI 0 AH)
(mem/u/c/i:QI (reg/f:QI 20) [2 S1 A16])) -1 (nil))
(insn 8 7 9 vol.c:3 (set (mem/v/c/i:QI (plus:QI (reg/f:QI 14
virtual-stack-vars)
(const_int 1 [0x1])) [2 sc+1 S1 A16])
(reg:QI 1 AL)) -1 (nil))
(insn 9 8 0 vol.c:3 (set (subreg:QI (mem/v/c/i:HI (reg/f:QI 14
virtual-stack-vars) [2 sc+0 S2 A16]) 0)
(reg:QI 0 AH)) -1 (nil))
Now, the problem with this comes with insn 9 that has a subreg:QI of a
mem:HI it seems. The raw move we are trying to do is:
(set (mem/v/c/i:HI (reg/f:QI 14 virtual-stack-vars) [2 sc+0 S2 A16])
(mem/u/c/i:HI (reg/f:QI 20) [2 S2 A16]))
To do this we need to go through two QImode registers AL and AH and I
have as part of my port:
emit_move_insn(gen_rtx_REG(QImode, RAL), gen_lowpart(QImode,
operands[1]));
emit_move_insn(gen_rtx_REG(QImode, RAH), gen_highpart(QImode,
operands[1]));
emit_move_insn(gen_lowpart(QImode, operands[0]),
gen_rtx_REG(QImode, RAL));
emit_move_insn(gen_highpart(QImode, operands[0]),
gen_rtx_REG(QImode, RAH));
The problem here comes with gen_lowpart and gen_highpart applied to:
(mem/v/c/i:HI (reg/f:QI 14 virtual-stack-vars) [2 sc+0 S2 A16])
gen_lowpart generates: (mem/v/c/i:QI (plus:QI (reg/f:QI 14
virtual-stack-vars)(const_int 1 [0x1]))
but gen_highpart generates:
(subreg:QI (mem/v/c/i:HI (reg/f:QI 14 virtual-stack-vars) [2 sc+0 S2
A16]) 0)
Why is that? Any suggestion on solving this situation?
Cheers,
Paulo Matos
