On 09/08/14 07:57, Jiong Wang wrote:
Conceptually OK. Some questions/concerns about the implementation.
Hi Jeff,
thanks very much for your review.
It seems to me that what you're trying to describe on the RHS is
REG_P || CONSTANT_P
yes.
and actually I am trying to detect all rtx which contains any number
of RTX_CONST_OBJs and no more than one REG.
Note that CONSTANT_P will catch things like (high (symbol_ref)) and
(lo_sum (reg) (symbol_ref)) which are often used to build addresses on
some targets.
With that in mind, rather than using a for_each_rtx callback, test
if (REG_P (src) || CONSTANT_P (src))
Note that SRC, when it is a CONSTANT_P, may have a variety of forms
with embedded registers. You'll need to verify that all of those
registers are not assigned after the insn with the CONSTANT_P source
operand. Right now you only perform that check when SRC is a REG_P.
I am using the for_each_rtx because I want to scan "src" so that
any sub-operands are checked, the number of REG and non-constant
objects are record in "reg_found" and "nonconst_found". the embedded
register found also record in the "reg" field of the structure
"rtx_search_arg",
Constants in this context are going to satisfy CONSTANT_P, you don't
need to manually verify them. It will include simple constants and
constants which are built up out of multiple instructions (symbolic
constants in particular).
I suspect you still need the callback to verify the # of registers is
just 1 so that the later tests work. However, please don't use
for_each_rtx, we're moving away from that to a more efficient walker
FOR_EACH_SUBRTX.
Jeff
