[PATCH] D115962: [DSE] Make isRemovable() for calls more robust (NFCI)

[Nikita Popov via Phabricator via llvm-commits]

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We can only drop calls if they have an analyzable write, the return value is not used, they don't throw and they don't diverge. The last two conditions were previously not checked, because all the libcalls with analyzable writes already happened to satisfy those conditions anyway. This may not be true for generalizations (with D115904 <https://reviews.llvm.org/D115904> in mind).

No test changes because the necessary attributes are already inferred for supported libcalls.


https://reviews.llvm.org/D115962

Files:
  llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp


Index: llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
@@ -206,9 +206,9 @@
     }
   }
 
-  // note: only get here for calls with analyzable writes - i.e. libcalls
+  // note: only get here for calls with analyzable writes.
   if (auto *CB = dyn_cast<CallBase>(I))
-    return CB->use_empty();
+    return CB->use_empty() && CB->willReturn() && CB->doesNotThrow();
 
   return false;
 }


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