backend: fix mem2reg & regalloc

they were broken, especially for unstructured control flow. most
significant fix is to register allocator for temporaries that are used
before the first definition in the source order, e.g.:

    @1:
        %x = add %y, 1
        b @3
    @2
        %y = ...
        b @1

it's legal for %x to use %y there (assuming @2 dominates @1) but from
the point of view of the register allocator %y is defined and freed
and then used again, which broke things. the fix is to introduce phis
for this situation:

    @1:
        %y.1 = phi @2 %y
        %x = add %y.1, 1
        b @3
    @2
        %y = ...
        b @1

then regalloc phi handling code makes it work

1 files changed, 9 insertions, 0 deletions

diff --git a/common.h b/common.h
index a47837a..252cfa4 100644
--- a/common.h
+++ b/common.h
@@ -367,6 +367,12 @@ xbgrow_(void **p, size_t n)
 #define xbgrow(p, n) xbgrow_((void **)(p), (n) * sizeof**(p))
 #define xbpush(p, n, x) (xbgrow(p, (*(n) + 1)), (*(p))[(*(n))++] = (x))
 #define xbfree(p) ((p) ? free(&xbcap_(p)) : (void)0)
+#define xbcap(p) ((p) ? xbcap_(p) / sizeof*(p) : 0)
+#define xbgrowz(p, n) do {                       \
+   size_t tmp = *(p) ? xbcap_(*(p)) : 0;         \
+   xbgrow(p, n);                                 \
+   memset((char*)*(p)+tmp, 0, xbcap_(*(p))-tmp); \
+} while (0)
 
 struct arena *newarena(uint chunksiz);
 void *alloc(struct arena **, uint siz, uint align);
@@ -431,6 +437,9 @@ int pmap_set_(struct pmapbase *, void **v, uint vsiz, const void *k);
 #define pmap_get(m, k) (((m)->tmp = pmap_get_(&(m)->mb, k)) < 0 ? NULL : &(m)->v[(m)->tmp])
 #define pmap_set(m, k, x) ((m)->tmp = pmap_set_(&(m)->mb, (void **)&(m)->v, sizeof*(m)->v, k), \
                            (m)->v[(m)->tmp] = (x))
+#define pmap_each(m,kx,pvx) \
+   for (int _i = 0; _i < (m)->mb.N && ((kx) = (m)->mb.k[_i], (pvx) = &(m)->v[_i], 1); ++_i) \
+      if (kx)
 
 static inline bool
 bstest(const struct bitset *bs, uint i)