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| author | Ben Gamari <ben@smart-cactus.org> | 2019-06-10 09:25:57 -0400 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2019-06-14 10:48:51 -0400 |
| commit | 5279dda861f6a5cc804be88dc5f0ff2442660149 (patch) | |
| tree | 1ef81e731c456a2d30ee36430077d96399ebc369 /testsuite/tests/codeGen | |
| parent | effdd948056923f3bc03688c24d7e0339d6272f5 (diff) | |
| download | haskell-5279dda861f6a5cc804be88dc5f0ff2442660149.tar.gz | |
PrelRules: Don't break let/app invariant in shiftRule
Previously shiftRule would rewrite as invalid shift like
```
let x = I# (uncheckedIShiftL# n 80)
in ...
```
to
```
let x = I# (error "invalid shift")
in ...
```
However, this breaks the let/app invariant as `error` is not
okay-for-speculation. There isn't an easy way to avoid this so let's not
try. Instead we just take advantage of the undefined nature of invalid
shifts and return zero.
Fixes #16742.
Diffstat (limited to 'testsuite/tests/codeGen')
| -rw-r--r-- | testsuite/tests/codeGen/should_run/T16449_2.hs | 4 | ||||
| -rw-r--r-- | testsuite/tests/codeGen/should_run/T16449_2.stderr | 1 | ||||
| -rw-r--r-- | testsuite/tests/codeGen/should_run/T16449_2.stdout | 2 | ||||
| -rw-r--r-- | testsuite/tests/codeGen/should_run/all.T | 2 |
4 files changed, 7 insertions, 2 deletions
diff --git a/testsuite/tests/codeGen/should_run/T16449_2.hs b/testsuite/tests/codeGen/should_run/T16449_2.hs index 3424d43e25..acb885369c 100644 --- a/testsuite/tests/codeGen/should_run/T16449_2.hs +++ b/testsuite/tests/codeGen/should_run/T16449_2.hs @@ -5,5 +5,9 @@ module Main where import GHC.Prim import GHC.Int +-- Test that large unchecked shifts, which constitute undefined behavior, do +-- not crash the compiler and instead evaluate to 0. +-- See Note [Guarding against silly shifts] in PrelRules. + -- Shift should be larger than the word size (e.g. 64 on 64-bit) for this test. main = print (I# (uncheckedIShiftL# 1# 1000#)) diff --git a/testsuite/tests/codeGen/should_run/T16449_2.stderr b/testsuite/tests/codeGen/should_run/T16449_2.stderr deleted file mode 100644 index 869a5b0f91..0000000000 --- a/testsuite/tests/codeGen/should_run/T16449_2.stderr +++ /dev/null @@ -1 +0,0 @@ -T16449_2: Bad shift length 1000 diff --git a/testsuite/tests/codeGen/should_run/T16449_2.stdout b/testsuite/tests/codeGen/should_run/T16449_2.stdout new file mode 100644 index 0000000000..77ac542d4f --- /dev/null +++ b/testsuite/tests/codeGen/should_run/T16449_2.stdout @@ -0,0 +1,2 @@ +0 + diff --git a/testsuite/tests/codeGen/should_run/all.T b/testsuite/tests/codeGen/should_run/all.T index 5545c9ebb0..535ca8651e 100644 --- a/testsuite/tests/codeGen/should_run/all.T +++ b/testsuite/tests/codeGen/should_run/all.T @@ -196,4 +196,4 @@ test('T15892', extra_run_opts('+RTS -G1 -A32k -RTS') ], compile_and_run, ['-O']) test('T16617', normal, compile_and_run, ['']) -test('T16449_2', [expect_broken_for(16742, ['dyn', 'ghci', 'optasm', 'threaded2']), exit_code(1)], compile_and_run, ['']) +test('T16449_2', exit_code(0), compile_and_run, ['']) |