> From: Jamie Prescott <jpre...@yahoo.com>
> To: gcc@gcc.gnu.org
> Sent: Friday, May 22, 2009 10:36:47 AM
> Subject: Seeking suggestion
>
>
> Suppose you're writing the backend for a VM supporting two architectures, in
> which
> one of them clobbers the CC registers for certain instructions, while the
> other
> does not.
> The instructions themselves are exactly the same.
> What is the best/shortest/more-elegant way to write this, possibly w/out
> duplicating the
> instructions?
> I know I can write a define_expand and redirect, based on the TARGET, to two
> different
> instructions (one with "clobber", the other w/out), but that's basically
> three
> declarations
> for each insns. Is there a shorter way?
I ended up doing something like this (long way, but the only one I know of).
Example, for addsi3:
(define_insn "addsi3_xxx2"
[(set (match_operand:SI 0 "fullreg_operand" "=r,r")
(plus:SI (match_operand:SI 1 "fullreg_operand" "0,r")
(match_operand:SI 2 "fullreg_or_imm_operand" "rn,rn")))]
""
"@
add\t%0,%2,%0
add\t%1,%2,%0"
)
(define_insn "addsi3_xxx"
[(set (match_operand:SI 0 "fullreg_operand" "=r,r")
(plus:SI (match_operand:SI 1 "fullreg_operand" "0,r")
(match_operand:SI 2 "fullreg_or_imm_operand" "rn,rn")))
(clobber (reg:CC CC_REG))]
""
"@
add\t%0,%2,%0
add\t%1,%2,%0"
)
(define_expand "addsi3"
[(set (match_operand:SI 0 "fullreg_operand" "=r,r")
(plus:SI (match_operand:SI 1 "fullreg_operand" "0,r")
(match_operand:SI 2 "fullreg_or_imm_operand" "rn,rn")))]
""
{
if (!TARGET_XXX2)
emit_insn(gen_addsi3_xxx(operands[0], operands[1], operands[2]));
else
emit_insn(gen_addsi3_xxx2(operands[0], operands[1], operands[2]));
DONE;
}
)
But now I get and invalid rtx sharing from the push/pop parallels:
xxxx.c: In function 'test_dashr':
xxxx.c:32: error: invalid rtl sharing found in the insn
(insn 26 3 28 2 xxxx.c:26 (parallel [
(insn/f 25 0 0 (set (reg/f:SI 51 SP)
(minus:SI (reg/f:SI 51 SP)
(const_int 4 [0x4]))) -1 (nil))
(set/f (mem:SI (reg/f:SI 51 SP) [0 S4 A8])
(reg:SI 8 r8))
]) -1 (nil))
xxxx.c:32: error: shared rtx
(insn/f 25 0 0 (set (reg/f:SI 51 SP)
(minus:SI (reg/f:SI 51 SP)
(const_int 4 [0x4]))) -1 (nil))
xxxx.c:32: internal compiler error: internal consistency failure
Any insights?
Thanks,
- Jamie
