[llvm] [InstCombine] Preserve metadata from orig load in select fold. (PR #115605)

[Nikita Popov via llvm-commits]

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@@ -1065,6 +1065,25 @@ Instruction *InstCombinerImpl::visitLoadInst(LoadInst &LI) {
         V1->setAtomic(LI.getOrdering(), LI.getSyncScopeID());
         V2->setAlignment(Alignment);
         V2->setAtomic(LI.getOrdering(), LI.getSyncScopeID());
+        // Can copy any metadata that cannot trigger UB. In particular do not
+        // copy !noundef or !invariant.load.
+        unsigned SafeMDKinds[] = {LLVMContext::MD_dbg,
+                                  LLVMContext::MD_tbaa,
+                                  LLVMContext::MD_prof,
+                                  LLVMContext::MD_fpmath,
+                                  LLVMContext::MD_tbaa_struct,
+                                  LLVMContext::MD_alias_scope,
+                                  LLVMContext::MD_noalias,
+                                  LLVMContext::MD_nontemporal,
+                                  LLVMContext::MD_mem_parallel_loop_access,
+                                  LLVMContext::MD_access_group,
+                                  LLVMContext::MD_nonnull,
+                                  LLVMContext::MD_align,
+                                  LLVMContext::MD_dereferenceable,
+                                  LLVMContext::MD_dereferenceable_or_null,
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nikic wrote:

dereferenceable is IUB.

https://github.com/llvm/llvm-project/pull/115605