[llvm] a80a802 - IROutliner: Use ValueMapper to remap constants in a function (#134850)

[via llvm-commits]

Author: Matt Arsenault
Date: 2025-04-10T22:31:02+02:00
New Revision: a80a802d2f077257bcfee3aec67ea12dfc4e94da

URL: https://github.com/llvm/llvm-project/commit/a80a802d2f077257bcfee3aec67ea12dfc4e94da
DIFF: https://github.com/llvm/llvm-project/commit/a80a802d2f077257bcfee3aec67ea12dfc4e94da.diff

LOG: IROutliner: Use ValueMapper to remap constants in a function (#134850)

Stop relying on the uselist of constants, which also required filtering
the uses that are in the correct function. I'm not sure why this pass is
doing its own cloning instead of building the value map while doing its
cloning.

Added: 
    

Modified: 
    llvm/lib/Transforms/IPO/IROutliner.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/IPO/IROutliner.cpp b/llvm/lib/Transforms/IPO/IROutliner.cpp
index fd76d3a32049c..8c5946fb07c65 100644
--- a/llvm/lib/Transforms/IPO/IROutliner.cpp
+++ b/llvm/lib/Transforms/IPO/IROutliner.cpp
@@ -24,6 +24,7 @@
 #include "llvm/IR/PassManager.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Transforms/IPO.h"
+#include "llvm/Transforms/Utils/ValueMapper.h"
 #include <optional>
 #include <vector>
 
@@ -1930,29 +1931,25 @@ replaceArgumentUses(OutlinableRegion &Region,
 /// \param Region [in] - The region of extracted code to be changed.
 void replaceConstants(OutlinableRegion &Region) {
   OutlinableGroup &Group = *Region.Parent;
+  Function *OutlinedFunction = Group.OutlinedFunction;
+  ValueToValueMapTy VMap;
+
   // Iterate over the constants that need to be elevated into arguments
   for (std::pair<unsigned, Constant *> &Const : Region.AggArgToConstant) {
     unsigned AggArgIdx = Const.first;
-    Function *OutlinedFunction = Group.OutlinedFunction;
     assert(OutlinedFunction && "Overall Function is not defined?");
     Constant *CST = Const.second;
     Argument *Arg = Group.OutlinedFunction->getArg(AggArgIdx);
     // Identify the argument it will be elevated to, and replace instances of
     // that constant in the function.
-
-    // TODO: If in the future constants do not have one global value number,
-    // i.e. a constant 1 could be mapped to several values, this check will
-    // have to be more strict.  It cannot be using only replaceUsesWithIf.
-
+    VMap[CST] = Arg;
     LLVM_DEBUG(dbgs() << "Replacing uses of constant " << *CST
                       << " in function " << *OutlinedFunction << " with "
-                      << *Arg << "\n");
-    CST->replaceUsesWithIf(Arg, [OutlinedFunction](Use &U) {
-      if (Instruction *I = dyn_cast<Instruction>(U.getUser()))
-        return I->getFunction() == OutlinedFunction;
-      return false;
-    });
+                      << *Arg << '\n');
   }
+
+  RemapFunction(*OutlinedFunction, VMap,
+                RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
 }
 
 /// It is possible that there is a basic block that already performs the same