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authorQuentin Carbonneaux <quentin@c9x.me>2019-04-11 19:36:13 +0200
committerQuentin Carbonneaux <quentin@c9x.me>2019-04-11 20:18:20 +0200
commit81da1cdebb213077a1ce2c1aaed051de0751e13c (patch)
tree0d4022e2db324543bf9e0caf802043a5b11495d7 /cfg.c
parentd84f5fcbb75dcf8f6ff1f12e7509d05598a4b561 (diff)
downloadroux-81da1cdebb213077a1ce2c1aaed051de0751e13c.tar.gz
properly detect ssa form
Previously, we would skip ssa construction when
a temporary has a single definition.  This is
only part of the ssa invariant: we must also
check that all uses are dominated by the single
definition.  The new code does this.

In fact, qbe does not store all the dominators
for a block, so instead of walking the idom
linked list we use a rough heuristic and declare
conservatively that B0 dominates B1 when one of
the two conditions is true:

  a. B0 is the start block
  b. B0 is B1

Some measurements on a big file from Michael
Forney show that the code is still as fast as
before this patch.
Diffstat (limited to 'cfg.c')
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