[llvm] [ReachingDefAnalysis] Fix management of MBBFrameObjsReachingDefs (PR #124943)

[Michael Maitland via llvm-commits]

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@@ -344,15 +342,10 @@ int ReachingDefAnalysis::getReachingDef(MachineInstr *MI, Register Reg) const {
     int Key = FrameIndex - ObjectIndexBegin;
 
     // Check that there was a reaching def.
-    auto Lookup1 = MBBFrameObjsReachingDefs.find(MBBNumber);
-    if (Lookup1 == MBBFrameObjsReachingDefs.end())
-      return LatestDef;
-    auto &InnerMap = Lookup1->second;
-    auto Lookup2 = InnerMap.find(Key);
-    if (Lookup2 == InnerMap.end())
+    auto Lookup = MBBFrameObjsReachingDefs.find({MBBNumber, Key});
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michaelmaitland wrote:

There is no testing for a non-zero ObjectIndexBegin, so it ended up behaving as if Key == FrameIndex. Do you want me  to add a test for a non-zero ObjectIndexBegin?

https://github.com/llvm/llvm-project/pull/124943