I'm having trouble understanding part of the machine description
for PowerPC floating point operations.
There are a number of places where there are pairs of templates,
one with define_expand, the other with define_insn or
define_insn_and_split. For example, the fp negate templates:
(define_expand "negsf2"
[(set (match_operand:SF 0 "gpc_reg_operand" "")
(neg:SF (match_operand:SF 1 "gpc_reg_operand" "")))]
"TARGET_HARD_FLOAT"
"")
(define_insn "*negsf2"
[(set (match_operand:SF 0 "gpc_reg_operand" "=f")
(neg:SF (match_operand:SF 1 "gpc_reg_operand" "f")))]
"TARGET_HARD_FLOAT && TARGET_FPRS"
"fneg %0,%1"
[(set_attr "type" "fp")])
I've read the docs (sect 13.15) which describe define_expand,
but I have a feeling that I'm missing something that would make
it clear how these two templates interact. Clearly, the define_insn
template says that when the insn pattern is found, generate the
"fneg" instruction. What is the define_expand template doing?
Thanks!
--
Michael Eager [EMAIL PROTECTED]
1960 Park Blvd., Palo Alto, CA 94306 650-325-8077
