Accessing the final statement of an sblock via tail doesn't work in an
empty sblock because tail points to sblock->statements and thus the cast is
invalid. This bug has be lurking for a long time, but for some reason the
cse stuff tickled it (thankfully!!!).
flow_analyze_statement uses the statement type to quickly determin which
operands are inputs and which are outputs. It takes (optional) sets for
used variables, defined variables and killed variables (only partially
working, but I don't actually use kill sets yet). It also takes an optional
array for storing the operands: index 0 is the output, 1-3 are the inputs.
flow_analyze_statement clears any given sets on entry.
Live variable analysis now uses the sets rather than individual vars. Much
cleaner code :).
Dags are completely broken.
The types are expression, assignment, pointer assignment (ie, write to a
dereferenced pointer), move (special case of pointer assignment), state,
function call/return, and flow control. With this classification, it will
be easier (less code:) to determine which operands are inputs and which are
outputs.
Using "=" was rather confusing, so changing it to "<CONV>" seems to be a
good idea. As the string is used only for selecting opcodes at compile
time, only qfcc is affected.
They're now dot_sblock.c and print_sblock. The new names both better
reflect their purpose and free up "flow" for outputting the real flow
analysis graphs.
It turns out no code was being generated for x = *y. Ouch. I suspect I need
to take a better look at expr_deref at some time in the not too distant
future.
Conflicts:
tools/qfcc/source/statements.c
When mering if/goto (ie, if skipping a goto), the rest of the dead code
remover is used to delete the goto. That part of the code unuses the goto's
label. The if was getting the goto's label without the lable's used count
being incremented (the usaged temporarily increases by one). I have no idea
why the problem showed up randomly, but this seems to fix it (it fixes /a/
bug, anyway).
The naive implementation of the if/goto merging was letting the old target
of the if get dropped because the block would lose its label and thus be
judged unreachable because the preceeding goto block was still in the list.
Instead, when the if/goto are "merged", mark the goto block as unreachable,
the following block as reachable, and break out of the analysis loop to
force the removal of the goto block. Since the dead block removal function
loops until no action is taken, all other dead blocks will be removed.
The output can be controlled via --block-dot (not yet documented). The
files a named <sourcefile>.<function>.<stage>.dot. Currently, stage will be
one of "initial" (after expression to statement conversion), "thread"
(after jump threading), "dead" (after dead block removal), "final" (final
state before actual code emission).
Labels can be shared between multiple flow-control instructions, so use the
label's used counter to determine when to remove the label. This was
causing problems with the jump threading.
