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

[Stepan Dyatkovskiy]

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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