[llvm-commits] [LLVM, loop-unswitch, bugfix for #11429] Wrong behaviour for switches.

[Stepan Dyatkovskiy]

ping.

-Stepan.
Stepan Dyatkovskiy wrote:
> ping.
>
> -Stepan.
>
> Stepan Dyatkovskiy wrote:
>> ping.
>>
>> -Stepan.
>>
>> Stepan Dyatkovskiy wrote:
>>> ping.
>>>
>>> -Stepan
>>>
>>> Stepan Dyatkovskiy wrote:
>>>> Hi all. Please find the patch in attachment for review. Regression tests
>>>> are attached in separated patch.
>>>>
>>>> Short tests description:
>>>>
>>>> 2011-11-18-SimpleSwitch.ll
>>>> Check simple that simple switch will totally unswitched:
>>>>
>>>> for (...)
>>>> switch(c) {
>>>> case 0: inc(); break;
>>>> case 1: dec(); break;
>>>> default: goto loop_exit;
>>>> }
>>>>
>>>> loop_exit:
>>>> ...
>>>>
>>>> Result of processing should be 2 additional loops for c == 0 and for c
>>>> == 1.
>>>>
>>>>
>>>> 2011-11-18-TwoSwitches.ll
>>>> Check that second switch will unswitched too. Check that switches will
>>>> not unswitched again in new loop:
>>>>
>>>> Initially we have the next:
>>>>
>>>> for (...) {
>>>> switch(c) {
>>>> case 0: inc(); break;
>>>> }
>>>> switch(d) {
>>>> case 0: inc(); break;
>>>> }
>>>> }
>>>>
>>>> After optimization we should got 3 additional loops: when (c == 0&&    d
>>>> == 0), when (c == 0&&    d != 0) and when (c != 0&&    d == 0). Original
>>>> loop will activated for (c != 0&&    d != 0):
>>>>
>>>> if (c == 0&&    d == 0) {
>>>> for (...) ... // All is clear here. Two "switch(0)" instructions.
>>>> } else if (c == 0&&    d != 0) {
>>>> for (...) {
>>>> switch (0) { // c == 0
>>>> case 0: inc(); break;
>>>> }
>>>> switch (d) {
>>>> case 0: goto unreachable; // CHECK: That it will not unswitched
>>>> // again, since it looks "trivial",
>>>> // see LoopUnswitch::IsTrivialUnswitchCondition
>>>> }
>>>> }
>>>> } else if (c != 0&&    d == 0) {
>>>> // the same...
>>>> ...
>>>> } else { // if (c != 0&&    d != 0)
>>>> // Original totally unswitched loop:
>>>> switch (c) {
>>>> case 0: goto unreachable;
>>>> }
>>>> switch (d) {
>>>> case 0: goto unreachable;
>>>> }
>>>> }
>>>>
>>>> Stepan.
>>>>
>>>>
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