[clang] [llvm] [LV] Support generating masks for switch terminators. (PR #99808)

[via llvm-commits]

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@@ -7763,6 +7763,41 @@ VPValue *VPRecipeBuilder::createEdgeMask(BasicBlock *Src, BasicBlock *Dst) {
 
   VPValue *SrcMask = getBlockInMask(Src);
 
+  if (auto *SI = dyn_cast<SwitchInst>(Src->getTerminator())) {
+    // Create mask where the terminator in Src is a switch. We need to handle 2
+    // separate cases:
+    // 1. Dst is not the default desintation. Dst is reached if any of the cases
+    // with destination == Dst are taken. Join the conditions for each case
+    // where destination == Dst using a logical OR.
+    // 2. Dst is the default destination. Dst is reached if none of the cases
+    // with destination != Dst are taken. Join the conditions for each case
+    // where the destination is != Dst using a logical OR and negate it.
+    VPValue *Mask = nullptr;
+    VPValue *Cond = getVPValueOrAddLiveIn(SI->getCondition(), Plan);
+    bool IsDefault = SI->getDefaultDest() == Dst;
+    for (auto &C : SI->cases()) {
+      if (IsDefault) {
+        if (C.getCaseSuccessor() == Dst)
+          continue;
+      } else if (C.getCaseSuccessor() != Dst)
+        continue;
+
+      VPValue *Eq = EdgeMaskCache.lookup({Src, C.getCaseSuccessor()});
+      if (!Eq) {
+        VPValue *V = getVPValueOrAddLiveIn(C.getCaseValue(), Plan);
+        Eq = Builder.createICmp(CmpInst::ICMP_EQ, Cond, V);
+      }
+      if (Mask)
+        Mask = Builder.createOr(Mask, Eq);
----------------
ayalz wrote:

```suggestion
        Mask = Builder.createLogicalOr(Mask, Eq);
```

https://github.com/llvm/llvm-project/pull/99808