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

[Stepan Dyatkovskiy]

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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