diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
diff --git a/llvm/lib/CodeGen/TargetPassConfig.cpp b/llvm/lib/CodeGen/TargetPassConfig.cpp
@@ -600,8 +600,14 @@ void TargetPassConfig::addIRPasses() {
       addPass(createPrintFunctionPass(dbgs(), "\n\n*** Code after LSR ***\n"));
   }
 
-  if (getOptLevel() != CodeGenOpt::None && EnableMergeICmps) {
-    addPass(createMergeICmpsPass());
+  if (getOptLevel() != CodeGenOpt::None) {
+    // 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 lowering hook.
+    if (EnableMergeICmps)
+      addPass(createMergeICmpsPass());
+    addPass(createExpandMemCmpPass());
   }
 
   // Run GC lowering passes for builtin collectors

diff --git a/llvm/lib/Transforms/Scalar/CMakeLists.txt b/llvm/lib/Transforms/Scalar/CMakeLists.txt
@@ -9,6 +9,7 @@ add_llvm_library(LLVMScalarOpts
   DeadStoreElimination.cpp
   DivRemPairs.cpp
   EarlyCSE.cpp
+  ExpandMemCmp.cpp
   FlattenCFGPass.cpp
   Float2Int.cpp
   GuardWidening.cpp

diff --git a/llvm/lib/Transforms/Scalar/ExpandMemCmp.cpp b/llvm/lib/Transforms/Scalar/ExpandMemCmp.cpp
diff --git a/llvm/lib/Transforms/Scalar/Scalar.cpp b/llvm/lib/Transforms/Scalar/Scalar.cpp
@@ -48,6 +48,7 @@ void llvm::initializeScalarOpts(PassRegistry &Registry) {
   initializeNewGVNLegacyPassPass(Registry);
   initializeEarlyCSELegacyPassPass(Registry);
   initializeEarlyCSEMemSSALegacyPassPass(Registry);
+  initializeExpandMemCmpPassPass(Registry);
   initializeGVNHoistLegacyPassPass(Registry);
   initializeGVNSinkLegacyPassPass(Registry);
   initializeFlattenCFGPassPass(Registry);

diff --git a/llvm/test/CodeGen/Generic/llc-start-stop.ll b/llvm/test/CodeGen/Generic/llc-start-stop.ll
@@ -13,15 +13,15 @@
 ; STOP-BEFORE-NOT: Loop Strength Reduction
 
 ; RUN: llc < %s -debug-pass=Structure -start-after=loop-reduce -o /dev/null 2>&1 | FileCheck %s -check-prefix=START-AFTER
-; START-AFTER: -machine-branch-prob -gc-lowering
+; START-AFTER: -machine-branch-prob -expandmemcmp
 ; START-AFTER: FunctionPass Manager
-; START-AFTER-NEXT: Lower Garbage Collection Instructions
+; START-AFTER-NEXT: Expand memcmp() to load/stores
 
 ; RUN: llc < %s -debug-pass=Structure -start-before=loop-reduce -o /dev/null 2>&1 | FileCheck %s -check-prefix=START-BEFORE
 ; START-BEFORE: -machine-branch-prob -domtree
 ; START-BEFORE: FunctionPass Manager
 ; START-BEFORE: Loop Strength Reduction
-; START-BEFORE-NEXT: Lower Garbage Collection Instructions
+; START-BEFORE-NEXT: Expand memcmp() to load/stores
 
 ; RUN: not llc < %s -start-before=nonexistent -o /dev/null 2>&1 | FileCheck %s -check-prefix=NONEXISTENT-START-BEFORE
 ; RUN: not llc < %s -stop-before=nonexistent -o /dev/null 2>&1 | FileCheck %s -check-prefix=NONEXISTENT-STOP-BEFORE

diff --git a/llvm/test/CodeGen/X86/memcmp-optsize.ll b/llvm/test/CodeGen/X86/memcmp-optsize.ll
diff --git a/llvm/test/CodeGen/X86/memcmp.ll b/llvm/test/CodeGen/X86/memcmp.ll
diff --git a/llvm/test/Transforms/ExpandMemCmp/X86/lit.local.cfg b/llvm/test/Transforms/ExpandMemCmp/X86/lit.local.cfg
@@ -0,0 +1,3 @@
+if not 'X86' in config.root.targets:
+    config.unsupported = True
+
diff --git a/...t/Transforms/CodeGenPrepare/X86/memcmp.ll → ...est/Transforms/ExpandMemCmp/X86/memcmp.ll b/...t/Transforms/CodeGenPrepare/X86/memcmp.ll → ...est/Transforms/ExpandMemCmp/X86/memcmp.ll
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,3 @@
		if not 'X86' in config.root.targets:
		config.unsupported = True