On 11/02/2015 04:06 PM, Jeff Law wrote:
On 10/30/2015 09:09 PM, David Wohlferd wrote:
I have updated the non-md text with (most of) the changes I think it
needs (attached). These changes are pleasantly minor, mostly just
adding some example text and a bit of formatting.
However. Trying to actually use the information on this page is turning
up some problems.
I think the fundamental problem here is we ought not be exposing those
modifiers to the user. They're inherently tied to the details of the
register allocation and reloading passes.
This is what I'm thinking as well. Why would a user even need
multi-alternative constraints in inline asm? An insn template might be
instantiated in many different contexts and need to deal with different
flavors of operands, but inline asm code is generally unique and the
programmer writing it knows very well what the operands are supposed to
be (this one is a register, that one is an address, etc).
Choosing the most efficient form of a logical-or instruction is hardly a
good motivating example, either -- nobody writes inline asm to do that.
I'm under the impression that the primary uses of inline asm are
either to access machine instructions not exposed by builtins, or to
provide a block of highly tuned code replacing all/most of a C function
body.
-Sandra
