[llvm] [SimplifyCFG] Drop UB-implying metadata when hoisting past side effects (PR #226746)

[Nikita Popov via llvm-commits]

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@@ -2053,6 +2053,20 @@ bool SimplifyCFGOpt::hoistCommonCodeFromSuccessors(Instruction *TI,
         I1->applyMergedLocation(I1->getDebugLoc(), I2->getDebugLoc());
         I2->eraseFromParent();
       }
+      // I1 now executes before the instructions we skipped.
+      unsigned SkippedFlags = 0;
+      for (const SuccIterPair &P : SuccIterPairs)
+        SkippedFlags |= P.second;
+      if (SkippedFlags & SkipImplicitControlFlow) {
+        // One of them may throw or not return, so I1 is speculated.
+        I1->dropUBImplyingAttrsAndMetadata();
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nikic wrote:

This bit looks fine.

https://github.com/llvm/llvm-project/pull/226746