[llvm] [ThinLTO][WPD] LICM a loop invariant check (PR #164862)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Teresa Johnson (teresajohnson)

<details>
<summary>Changes</summary>

Move a loop invariant check out of the innermost loop. I measured a
small but consistent thin link speedup from this change for a large
target (0.75%).


---
Full diff: https://github.com/llvm/llvm-project/pull/164862.diff


1 Files Affected:

- (modified) llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp (+6-6) 


``````````diff
diff --git a/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp b/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
index 6909a282b3129..5174e2361b66f 100644
--- a/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
+++ b/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
@@ -948,17 +948,17 @@ void llvm::updateVCallVisibilityInIndex(
     // linker, as we have no information on their eventual use.
     if (DynamicExportSymbols.count(P.first))
       continue;
+    // With validation enabled, we want to exclude symbols visible to regular
+    // objects. Local symbols will be in this group due to the current
+    // implementation but those with VCallVisibilityTranslationUnit will have
+    // already been marked in clang so are unaffected.
+    if (VisibleToRegularObjSymbols.count(P.first))
+      continue;
     for (auto &S : P.second.getSummaryList()) {
       auto *GVar = dyn_cast<GlobalVarSummary>(S.get());
       if (!GVar ||
           GVar->getVCallVisibility() != GlobalObject::VCallVisibilityPublic)
         continue;
-      // With validation enabled, we want to exclude symbols visible to regular
-      // objects. Local symbols will be in this group due to the current
-      // implementation but those with VCallVisibilityTranslationUnit will have
-      // already been marked in clang so are unaffected.
-      if (VisibleToRegularObjSymbols.count(P.first))
-        continue;
       GVar->setVCallVisibility(GlobalObject::VCallVisibilityLinkageUnit);
     }
   }

``````````

</details>


https://github.com/llvm/llvm-project/pull/164862