[PATCH] D139970: [llvm][CallBrPrepare] use SSAUpdater to use intrinsic value

[Nick Desaulniers via Phabricator via llvm-commits]

nickdesaulniers added inline comments.


================
Comment at: llvm/lib/CodeGen/CallBrPrepare.cpp:180
+
+    for (Use &U : CBR->uses()) {
+      PrintDebugDomInfo(DT, U, LandingPad, /*IsDefaultDest*/ false);
----------------
nickdesaulniers wrote:
> This will loop infinitely if we update a `Use` in flight;
> 
> ```
> diff --git a/llvm/lib/CodeGen/CallBrPrepare.cpp b/llvm/lib/CodeGen/CallBrPrepare.cpp
> index bbf14c5f8e97..7e9ad9593f45 100644
> --- a/llvm/lib/CodeGen/CallBrPrepare.cpp
> +++ b/llvm/lib/CodeGen/CallBrPrepare.cpp
> @@ -176,8 +176,11 @@ void CallBrPrepare::UpdateSSA(DominatorTree *DT) const {
>      CallBrInst *CBR = Pair.second;
>      BasicBlock *DefaultDest = CBR->getDefaultDest();
>      BasicBlock *LandingPad = Intrinsic->getParent();
> +    SmallPtrSet<Use *, 2> Visited;
>  
>      for (Use &U : CBR->uses()) {
> +      if (Visited.insert(&U).second)
> +        continue;
>        PrintDebugDomInfo(DT, U, LandingPad, /*IsDefaultDest*/ false);
>        PrintDebugDomInfo(DT, U, DefaultDest, /*IsDefaultDest*/ true);
> ```
errr, more like:
```
diff --git a/llvm/lib/CodeGen/CallBrPrepare.cpp b/llvm/lib/CodeGen/CallBrPrepare.cpp
index bbf14c5f8e97..c9542de943a2 100644
--- a/llvm/lib/CodeGen/CallBrPrepare.cpp
+++ b/llvm/lib/CodeGen/CallBrPrepare.cpp
@@ -190,8 +190,9 @@ void CallBrPrepare::UpdateSSA(DominatorTree *DT) const {
         continue;
       }
 
-      // If the Use is dominated by the default dest, do not touch it.
-      if (DT->dominates(DefaultDest, U))
+      // If the Use is in the default dest BasicBlock, or dominated by the
+      // default dest, do not touch it.
+      if (IsInSameBasicBlock(U, DefaultDest) || DT->dominates(DefaultDest, U))
         continue;
 
       SSAUpdate.Initialize(U->getType(), U->getName());
```


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https://reviews.llvm.org/D139970