Commit a838d1f7 authored by Joachim Breitner's avatar Joachim Breitner
Browse files

CmmSwitch: Do not trip over a case with no (valid) branches

This fixes #10245. I did not commit the test case, as it fails
unconditionally with a compiler built with -DDEBUG, so maybe it is bogus
Haskell anyways.
parent a1404e88
......@@ -88,7 +88,8 @@ minJumpTableOffset = 2
-- We use an Integer for the keys the map so that it can be used in switches on
-- unsigned as well as signed integers.
--
-- The map must not be empty.
-- The map may be empty (we prune out-of-range branches here, so it could be us
-- emptying it).
--
-- Before code generation, the table needs to be brought into a form where all
-- entries are non-negative, so that it can be compiled into a jump table.
......@@ -270,6 +271,7 @@ createSwitchPlan (SwitchTargets signed mbdef range m) =
--- Step 1: Splitting at large holes
---
splitAtHoles :: Integer -> M.Map Integer a -> [M.Map Integer a]
splitAtHoles _ m | M.null m = []
splitAtHoles holeSize m = map (\range -> restrictMap range m) nonHoles
where
holes = filter (\(l,h) -> h - l > holeSize) $ zip (M.keys m) (tail (M.keys m))
......@@ -282,7 +284,7 @@ splitAtHoles holeSize m = map (\range -> restrictMap range m) nonHoles
--- Step 2: Avoid small jump tables
---
-- We do not want jump tables below a certain size. This breaks them up
-- (into singleton maps, for now)
-- (into singleton maps, for now).
breakTooSmall :: M.Map Integer a -> [M.Map Integer a]
breakTooSmall m
| M.size m > minJumpTableSize = [m]
......
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