1 files changed, 14 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
index d451653533a..bd5d01c8ad2 100644
--- a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
+++ b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -246,6 +246,18 @@ void PassManagerBuilder::addInstructionCombiningPass(
   PM.add(createInstructionCombiningPass(ExpensiveCombines));
 }
 
+void PassManagerBuilder::addMemcmpPasses(legacy::PassManagerBase &PM) const {
+  if (OptLevel > 0) {
+    // The MergeICmpsPass tries to create memcmp calls by grouping sequences of
+    // loads and compares. ExpandMemCmpPass then tries to expand those calls
+    // into optimally-sized loads and compares. The transforms are enabled by a
+    // target transform info hook.
+    PM.add(createMergeICmpsLegacyPass());
+    PM.add(createExpandMemCmpPass());
+    PM.add(createEarlyCSEPass());
+  }
+}
+
 void PassManagerBuilder::populateFunctionPassManager(
     legacy::FunctionPassManager &FPM) {
   addExtensionsToPM(EP_EarlyAsPossible, FPM);
@@ -391,6 +403,7 @@ void PassManagerBuilder::addFunctionSimplificationPasses(
                    : createGVNPass(DisableGVNLoadPRE)); // Remove redundancies
   }
   MPM.add(createMemCpyOptPass());             // Remove memcpy / form memset
+  addMemcmpPasses(MPM);                       // Merge/Expand comparisons.
   MPM.add(createSCCPPass());                  // Constant prop with SCCP
 
   // Delete dead bit computations (instcombine runs after to fold away the dead
@@ -910,6 +923,7 @@ void PassManagerBuilder::addLTOOptimizationPasses(legacy::PassManagerBase &PM) {
   PM.add(NewGVN ? createNewGVNPass()
                 : createGVNPass(DisableGVNLoadPRE)); // Remove redundancies.
   PM.add(createMemCpyOptPass());            // Remove dead memcpys.
+  addMemcmpPasses(PM);                      // Merge/Expand comparisons.
 
   // Nuke dead stores.
   PM.add(createDeadStoreEliminationPass());