I was wondering if anyone could tell me how to write an (empty)
instruction pattern that does a truncate/extend conversion on a register
'in place'.
All the conversions I see are like this one in ia64/ia64.md:
(define_insn "extendsfdf2"
[(set (match_operand:DF 0 "fr_register_operand" "=f")
(float_extend:DF (match_operand:SF 1 "fr_register_operand" "f")))]
""
"fnorm.d %0 = %1"
[(set_attr "itanium_class" "fmac")])
Where the source and the destination may or may not be the same
register.
I am trying to create an empty extend operation I can use to 'convert' a
SFmode register into a DFmode register without actually generating any
code. Since I don't want this extend called in place of the normal one
I defined it as an UNSPEC operation instead of a float_extend operation
and since it doesn't generate any code and it cannot move the result
from one register to another I need to define it with only one operand.
But my attempt to do this doesn't seem to work and I was wondering if
anyone could tell me why or perhaps point me to an example of an
instruction that does a conversion in place that might help me
understand how to write such an instruction.
My attempt:
(define_insn "nop_extendsfdf"
[(set (match_operand:DF 0 "fr_register_operand" "+f")
(unspec:DF [(match_dup:SF 0)] UNSPEC_NOP_EXTEND))]
""
""
[(set_attr "itanium_class" "ignore")
(set_attr "predicable" "no")
(set_attr "empty" "yes")])
I think the match_dup may be wrong since I am using it with SF but the
original match_operand has DF. Do I need to make this modeless? Or is
there some other way to create an empty conversion instruction.
Steve Ellcey
[EMAIL PROTECTED]
