Add register lookup as another fallback computation for address-expressions (#85492)
The idea behind the address-expression is that it handles all the common
expressions that produce addresses. It handles actual valid expressions
that return a scalar, and it handles useful cases that the various
source languages don't support. At present, the fallback handles:
<symbol_name>{+-}<offset>
which isn't valid C but is very handy.
This patch adds handling of:
$<reg_name>
and
$<reg_name>{+-}<offset>
That's kind of pointless in C because the C expression parser handles
that expression already. But some languages don't have a straightforward
way to represent register values like this (swift) so having this
fallback is quite a quality of life improvement.
I added a test which tests that I didn't mess up either of these
fallbacks, though it doesn't test the actually handling of registers
that I added, since the expression parser for C succeeds in that case
and returns before this code gets run.
I will add a test on the swift fork for that checks that this works the
same way for a swift frame after this check.
llvm-project
2c76e88e - Add register lookup as another fallback computation for address-expressions (#85492)
