Fixes#147.
The Solver::reassign_in() method would previously not record fixed
register assignments for values that are already in the correct
register. The register would simply be marked as unavailable for the
solver.
This did have the effect of tripping up the sanity checks in
Solver::add_var() when that method was called with such a "reassigned"
value. The function can be called for a value that already has a fixed
assignment, but the sanity checks want to make sure the variable
constraints are compatible with the existing fixed assignment. When no
such assignment could be found, the method panicked.
To fix this, make sure that even identity reassignments are recorded
in the assignments vector. Instead, filter the identity assignments out
before scheduling a move sequence for the assignments.
Also add some debug tracing to the regalloc solver.
It's not necessary to explicitly track whether the last instruction is a
return; if the builder for the last block isn't filled by the time we reach
the end, it needs a return to fill it.
The phantom unreachable stack is only used when the real unreachable stack is
active, so it's sufficient to check whether the real unreachable stack is empty.
Use these encodings to test trapz.b1 and trapnz.b1.
When a b1 value is stored in a register, only the low 8 bits are valid.
This is so we can use the various setCC instructions to generate the b1
registers.
The legalizer can invalidate the dominator tree, but we don't actually
need a dominator tree during legalization, so defer the construction of
the domtree.
- Add an "invalid" state to the dominator tree along with clear() and
is_valid() methods to test it.
- Invalidate the dominator tree as part of legalization.
- Ensure that a valid dominator tree exists before the passes that need
it.
Together these features add up to a manual invalidation mechanism for
the dominator tree.
Future legalization patterns will have the ability to mutate the
flowgraph, so the domtree's list of RPO blocks is not a good guide for
iteration. Use the layout order instead. This will pick up any new EBBs
inserted.
The expansion of a heap_addr instruction depends on the type of heap and
its configuration, so this is handled by custom code.
Add a couple examples of heap access code to the language reference
manual.
Add preamble syntax for declaring static and dynamic heaps, and update
the langref section on heaps. Add IR support for heap references.
Remove the heap_load and heap_store as discussed in #144. We will use
heap_addr along with native load and store instructions in their place.
Add the heap_addr instruction and document its bounds checking
semantics.
