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author | Ömer Sinan Ağacan <omeragacan@gmail.com> | 2019-05-24 11:23:01 +0300 |
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committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2019-06-01 11:18:57 -0400 |
commit | 1503da32d26fb59fb6ebb620bfd0f8c08638f627 (patch) | |
tree | 8933e408efdbdec39de3e547b153aa1522c5714f /compiler/prelude/PrelRules.hs | |
parent | 76e5889017ee4ac688901d37f2fa684e807769b6 (diff) | |
download | haskell-1503da32d26fb59fb6ebb620bfd0f8c08638f627.tar.gz |
Fix rewriting invalid shifts to errors
Fixes #16449.
5341edf3 removed a code in rewrite rules for bit shifts, which broke the
"silly shift guard", causing generating invalid bit shifts or heap
overflow in compile time while trying to evaluate those invalid bit
shifts.
The "guard" is explained in Note [Guarding against silly shifts] in
PrelRules.hs.
More specifically, this was the breaking change:
--- a/compiler/prelude/PrelRules.hs
+++ b/compiler/prelude/PrelRules.hs
@@ -474,12 +474,11 @@ shiftRule shift_op
; case e1 of
_ | shift_len == 0
-> return e1
- | shift_len < 0 || wordSizeInBits dflags < shift_len
- -> return (mkRuntimeErrorApp rUNTIME_ERROR_ID wordPrimTy
- ("Bad shift length" ++ show shift_len))
This patch reverts this change.
Two new tests added:
- T16449_1: The original reproducer in #16449. This was previously
casing a heap overflow in compile time when CmmOpt tries to evaluate
the large (invalid) bit shift in compile time, using `Integer` as the
result type. Now it builds as expected. We now generate an error for
the shift as expected.
- T16449_2: Tests code generator for large (invalid) bit shifts.
Diffstat (limited to 'compiler/prelude/PrelRules.hs')
-rw-r--r-- | compiler/prelude/PrelRules.hs | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/compiler/prelude/PrelRules.hs b/compiler/prelude/PrelRules.hs index d9a1f8a023..bd18bfec63 100644 --- a/compiler/prelude/PrelRules.hs +++ b/compiler/prelude/PrelRules.hs @@ -467,13 +467,16 @@ shiftRule :: (DynFlags -> Integer -> Int -> Integer) -> RuleM CoreExpr -- Used for shift primops -- ISllOp, ISraOp, ISrlOp :: Word# -> Int# -> Word# -- SllOp, SrlOp :: Word# -> Int# -> Word# --- See Note [Guarding against silly shifts] shiftRule shift_op = do { dflags <- getDynFlags ; [e1, Lit (LitNumber LitNumInt shift_len _)] <- getArgs ; case e1 of _ | shift_len == 0 -> return e1 + -- See Note [Guarding against silly shifts] + | shift_len < 0 || shift_len > wordSizeInBits dflags + -> return $ mkRuntimeErrorApp rUNTIME_ERROR_ID wordPrimTy + ("Bad shift length " ++ show shift_len) -- Do the shift at type Integer, but shift length is Int Lit (LitNumber nt x t) |