[llvm] [SSAUpdaterBulk] Fix incorrect live-in values for a block. (PR #131762)

[Antonio Frighetto via llvm-commits]

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@@ -143,34 +136,65 @@ void SSAUpdaterBulk::RewriteAllUses(DominatorTree *DT,
     SmallVector<BasicBlock *, 32> IDFBlocks;
     SmallPtrSet<BasicBlock *, 32> LiveInBlocks;
     ComputeLiveInBlocks(UsingBlocks, DefBlocks, LiveInBlocks, PredCache);
-    IDF.resetLiveInBlocks();
     IDF.setLiveInBlocks(LiveInBlocks);
     IDF.calculate(IDFBlocks);
 
+    // Important: reserve sufficient buckets to prevent map growth. [1]
+    BBInfos.init(LiveInBlocks.size() + DefBlocks.size());
+
+    for (auto [BB, V] : R.Defines)
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antoniofrighetto wrote:

```suggestion
    for (const auto &[BB, V] : R.Defines)
```

https://github.com/llvm/llvm-project/pull/131762