[llvm-commits] [llvm] r168970 - in /llvm/trunk: lib/Transforms/Utils/SimplifyCFG.cpp test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll

[Chandler Carruth]

On Fri, Nov 30, 2012 at 12:47 AM, Matt Beaumont-Gay
<matthewbg at google.com> wrote:
> On Fri, Nov 30, 2012 at 12:39 AM, Duncan Sands <baldrick at free.fr> wrote:
>> Hi,
>>
>>
>> On 30/11/12 08:21, Matt Beaumont-Gay wrote:
>>>
>>> Hi Evan,
>>>
>>> With this change, we're seeing stage2/stage3 differences in our
>>> bootstrap build. I haven't looked at it in detail, but I wanted to
>>> give everybody a heads-up.
>>
>>
>>>> --- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
>>>> +++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Thu Nov 29 20:02:42
>>>> 2012
>>>> @@ -3511,22 +3511,29 @@
>>>>   static bool ShouldBuildLookupTable(SwitchInst *SI,
>>>>                                      uint64_t TableSize,
>>>>                                      const DataLayout *TD,
>>>> +                                   const TargetTransformInfo *TTI,
>>>>                               const SmallDenseMap<PHINode*, Type*>&
>>>> ResultTypes) {
>>>>     // The table density should be at least 40%. This is the same
>>>> criterion as for
>>>>     // jump tables, see SelectionDAGBuilder::handleJTSwitchCase.
>>>>     // FIXME: Find the best cut-off.
>>>>     if (SI->getNumCases() > TableSize || TableSize >= UINT64_MAX / 10)
>>>>       return false; // TableSize overflowed, or mul below might overflow.
>>>> -  if (SI->getNumCases() * 10 >= TableSize * 4)
>>>> -    return true;
>>>>
>>>>     // If each table would fit in a register, we should build it anyway.
>>>> +  bool AllFit = true;
>>>> +  bool HasIllegalType = false;
>>>>     for (SmallDenseMap<PHINode*, Type*>::const_iterator I =
>>>> ResultTypes.begin(),
>>>>          E = ResultTypes.end(); I != E; ++I) {
>>
>>
>> Dense map iteration isn't deterministic, so...
>
> Oh, of course. I was staring too hard at the actual changed lines. Thanks!

Should be fixed in r168989.