[PATCH] D128863: Add switch to use "source_file_name" instead of Module ID for globally promoted local

[Bill Wendling via Phabricator via llvm-commits]

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During LTO a local promoted to a global gets a unique suffix based
partially on the Module's ID. This has a problem, because the Module ID
is not the same as the original Module ID. So any tool that's validating
changes will see a change when there isn't one (i.e. the names of the
promoted locals are changed, but it doesn't reflect a real change).

Instead of using the Module's ID, we can use the "source_file_name" if
it exists to generate a unique identifier that doesn't change due to LTO
shenanigans.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D128863

Files:
  llvm/include/llvm/IR/ModuleSummaryIndex.h
  llvm/lib/Transforms/Utils/FunctionImportUtils.cpp


Index: llvm/lib/Transforms/Utils/FunctionImportUtils.cpp
===================================================================
--- llvm/lib/Transforms/Utils/FunctionImportUtils.cpp
+++ llvm/lib/Transforms/Utils/FunctionImportUtils.cpp
@@ -12,8 +12,13 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Transforms/Utils/FunctionImportUtils.h"
+#include "llvm/Support/CommandLine.h"
 using namespace llvm;
 
+static cl::opt<bool> UseSourceFileNameForPromotedLocals(
+    "use-source-file-name-for-promoted-locals", cl::Hidden,
+    cl::desc("Uses the source file name instead of the Module hash"));
+
 /// Checks if we should import SGV as a definition, otherwise import as a
 /// declaration.
 bool FunctionImportGlobalProcessing::doImportAsDefinition(
@@ -87,9 +92,31 @@
 std::string
 FunctionImportGlobalProcessing::getPromotedName(const GlobalValue *SGV) {
   assert(SGV->hasLocalLinkage());
+
   // For locals that must be promoted to global scope, ensure that
   // the promoted name uniquely identifies the copy in the original module,
   // using the ID assigned during combined index creation.
+  if (UseSourceFileNameForPromotedLocals &&
+      !SGV->getParent()->getSourceFileName().empty()) {
+    SmallString<256> Suffix(SGV->getParent()->getSourceFileName());
+    std::replace_if(Suffix.begin(), Suffix.end(),
+                    [&](char ch) {
+                      switch (ch) {
+                        case '/':
+                        case '\\':
+                        case '+':
+                        case '-':
+                        case '*':
+                        case ':':
+                          return true;
+                      }
+                      return isSpace(ch);
+                    }, '_');
+    std::replace(Suffix.begin(), Suffix.end(), '-', '_');
+    return ModuleSummaryIndex::getGlobalNameForLocal(
+        SGV->getName(), Suffix);
+  }
+
   return ModuleSummaryIndex::getGlobalNameForLocal(
       SGV->getName(),
       ImportIndex.getModuleHash(SGV->getParent()->getModuleIdentifier()));
Index: llvm/include/llvm/IR/ModuleSummaryIndex.h
===================================================================
--- llvm/include/llvm/IR/ModuleSummaryIndex.h
+++ llvm/include/llvm/IR/ModuleSummaryIndex.h
@@ -1459,10 +1459,15 @@
   /// Convenience method for creating a promoted global name
   /// for the given value name of a local, and its original module's ID.
   static std::string getGlobalNameForLocal(StringRef Name, ModuleHash ModHash) {
+    std::string Suffix = utostr((uint64_t(ModHash[0]) << 32) |
+                                ModHash[1]); // Take the first 64 bits
+    return getGlobalNameForLocal(Name, Suffix);
+  }
+
+  static std::string getGlobalNameForLocal(StringRef Name, StringRef Suffix) {
     SmallString<256> NewName(Name);
     NewName += ".llvm.";
-    NewName += utostr((uint64_t(ModHash[0]) << 32) |
-                      ModHash[1]); // Take the first 64 bits
+    NewName += Suffix;
     return std::string(NewName.str());
   }
 


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