[llvm] [licm] don't drop `MD_prof` when dropping other metadata (PR #152420)

[Snehasish Kumar via llvm-commits]

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@@ -552,14 +552,19 @@ void Instruction::dropUBImplyingAttrsAndUnknownMetadata(
   CB->removeRetAttrs(UBImplyingAttributes);
 }
 
-void Instruction::dropUBImplyingAttrsAndMetadata() {
+void Instruction::dropUBImplyingAttrsAndMetadata(ArrayRef<unsigned> Keep) {
   // !annotation metadata does not impact semantics.
   // !range, !nonnull and !align produce poison, so they are safe to speculate.
   // !noundef and various AA metadata must be dropped, as it generally produces
   // immediate undefined behavior.
-  unsigned KnownIDs[] = {LLVMContext::MD_annotation, LLVMContext::MD_range,
-                         LLVMContext::MD_nonnull, LLVMContext::MD_align};
-  dropUBImplyingAttrsAndUnknownMetadata(KnownIDs);
+  static const unsigned KnownIDs[] = {
+      LLVMContext::MD_annotation, LLVMContext::MD_range,
+      LLVMContext::MD_nonnull, LLVMContext::MD_align};
+  SmallVector<unsigned> KeepIDs;
+  KeepIDs.reserve(Keep.size() + std::size(KnownIDs));
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snehasish wrote:

Is this useful in practice? SmallVector<unsigned> might already allocate enough inline storage to not require an allocation for the small number of metadata types we have.

https://github.com/llvm/llvm-project/pull/152420