Index: lib/Passes/PassBuilder.cpp
===================================================================
--- lib/Passes/PassBuilder.cpp
+++ lib/Passes/PassBuilder.cpp
@@ -362,6 +362,9 @@
 
   invokePeepholeEPCallbacks(FPM, Level);
 
+  if (!isOptimizingForSize(Level))
+    FPM.addPass(PGOMemOPSizeOpt());
+
   FPM.addPass(TailCallElimPass());
   FPM.addPass(SimplifyCFGPass());
 
Index: test/Other/new-pm-defaults.ll
===================================================================
--- test/Other/new-pm-defaults.ll
+++ test/Other/new-pm-defaults.ll
@@ -118,12 +118,25 @@
 ; CHECK-O2-NEXT: Running pass: LibCallsShrinkWrapPass
 ; CHECK-O3-NEXT: Running pass: LibCallsShrinkWrapPass
 ; CHECK-EP-PEEPHOLE-NEXT: Running pass: NoOpFunctionPass
+; CHECK-O1-NEXT: Running pass: PGOMemOPSizeOpt
+; CHECK-O2-NEXT: Running pass: PGOMemOPSizeOpt
+; CHECK-O3-NEXT: Running pass: PGOMemOPSizeOpt
+; CHECK-O1-NEXT: Running analysis: BlockFrequencyAnalysis
+; CHECK-O1-NEXT: Running analysis: LoopAnalysis
+; CHECK-O1-NEXT: Running analysis: BranchProbabilityAnalysis
+; CHECK-O2-NEXT: Running analysis: BlockFrequencyAnalysis
+; CHECK-O2-NEXT: Running analysis: LoopAnalysis
+; CHECK-O2-NEXT: Running analysis: BranchProbabilityAnalysis
+; CHECK-O3-NEXT: Running analysis: BlockFrequencyAnalysis
+; CHECK-O3-NEXT: Running analysis: LoopAnalysis
+; CHECK-O3-NEXT: Running analysis: BranchProbabilityAnalysis
 ; CHECK-O-NEXT: Running pass: TailCallElimPass
 ; CHECK-O-NEXT: Running pass: SimplifyCFGPass
 ; CHECK-O-NEXT: Running pass: ReassociatePass
 ; CHECK-O-NEXT: Running pass: RequireAnalysisPass<{{.*}}OptimizationRemarkEmitterAnalysis
 ; CHECK-O-NEXT: Running pass: FunctionToLoopPassAdaptor<{{.*}}LoopStandardAnalysisResults{{.*}}>
-; CHECK-O-NEXT: Running analysis: LoopAnalysis
+; CHECK-Oz-NEXT: Running analysis: LoopAnalysis
+; CHECK-Os-NEXT: Running analysis: LoopAnalysis
 ; CHECK-O-NEXT: Running analysis: ScalarEvolutionAnalysis
 ; CHECK-O-NEXT: Running analysis: InnerAnalysisManagerProxy
 ; CHECK-O-NEXT: Starting Loop pass manager run.
@@ -190,8 +203,10 @@
 ; CHECK-O-NEXT: Running pass: FunctionToLoopPassAdaptor<{{.*}}LoopRotatePass
 ; CHECK-O-NEXT: Running pass: LoopDistributePass
 ; CHECK-O-NEXT: Running pass: LoopVectorizePass
-; CHECK-O-NEXT: Running analysis: BlockFrequencyAnalysis
-; CHECK-O-NEXT: Running analysis: BranchProbabilityAnalysis
+; CHECK-Os-NEXT: Running analysis: BlockFrequencyAnalysis
+; CHECK-Os-NEXT: Running analysis: BranchProbabilityAnalysis
+; CHECK-Oz-NEXT: Running analysis: BlockFrequencyAnalysis
+; CHECK-Oz-NEXT: Running analysis: BranchProbabilityAnalysis
 ; CHECK-O-NEXT: Running pass: LoopLoadEliminationPass
 ; CHECK-O-NEXT: Running analysis: LoopAccessAnalysis
 ; CHECK-O-NEXT: Running pass: InstCombinePass
Index: test/Other/new-pm-thinlto-defaults.ll
===================================================================
--- test/Other/new-pm-thinlto-defaults.ll
+++ test/Other/new-pm-thinlto-defaults.ll
@@ -112,12 +112,25 @@
 ; CHECK-O1-NEXT: Running pass: LibCallsShrinkWrapPass
 ; CHECK-O2-NEXT: Running pass: LibCallsShrinkWrapPass
 ; CHECK-O3-NEXT: Running pass: LibCallsShrinkWrapPass
+; CHECK-O1-NEXT: Running pass: PGOMemOPSizeOpt
+; CHECK-O2-NEXT: Running pass: PGOMemOPSizeOpt
+; CHECK-O3-NEXT: Running pass: PGOMemOPSizeOpt
+; CHECK-O1-NEXT: Running analysis: BlockFrequencyAnalysis
+; CHECK-O2-NEXT: Running analysis: BlockFrequencyAnalysis
+; CHECK-O3-NEXT: Running analysis: BlockFrequencyAnalysis
+; CHECK-O1-NEXT: Running analysis: LoopAnalysis
+; CHECK-O2-NEXT: Running analysis: LoopAnalysis
+; CHECK-O3-NEXT: Running analysis: LoopAnalysis
+; CHECK-O1-NEXT: Running analysis: BranchProbabilityAnalysis
+; CHECK-O2-NEXT: Running analysis: BranchProbabilityAnalysis
+; CHECK-O3-NEXT: Running analysis: BranchProbabilityAnalysis
 ; CHECK-O-NEXT: Running pass: TailCallElimPass
 ; CHECK-O-NEXT: Running pass: SimplifyCFGPass
 ; CHECK-O-NEXT: Running pass: ReassociatePass
 ; CHECK-O-NEXT: Running pass: RequireAnalysisPass<{{.*}}OptimizationRemarkEmitterAnalysis
 ; CHECK-O-NEXT: Running pass: FunctionToLoopPassAdaptor<{{.*}}LoopStandardAnalysisResults{{.*}}>
-; CHECK-O-NEXT: Running analysis: LoopAnalysis
+; CHECK-Os-NEXT: Running analysis: LoopAnalysis
+; CHECK-Oz-NEXT: Running analysis: LoopAnalysis
 ; CHECK-O-NEXT: Running analysis: ScalarEvolutionAnalysis
 ; CHECK-O-NEXT: Running analysis: InnerAnalysisManagerProxy
 ; CHECK-O-NEXT: Starting Loop pass manager run.
@@ -178,8 +191,10 @@
 ; CHECK-POSTLINK-O-NEXT: Running pass: FunctionToLoopPassAdaptor<{{.*}}LoopRotatePass
 ; CHECK-POSTLINK-O-NEXT: Running pass: LoopDistributePass
 ; CHECK-POSTLINK-O-NEXT: Running pass: LoopVectorizePass
-; CHECK-POSTLINK-O-NEXT: Running analysis: BlockFrequencyAnalysis
-; CHECK-POSTLINK-O-NEXT: Running analysis: BranchProbabilityAnalysis
+; CHECK-POSTLINK-Os-NEXT: Running analysis: BlockFrequencyAnalysis
+; CHECK-POSTLINK-Oz-NEXT: Running analysis: BlockFrequencyAnalysis
+; CHECK-POSTLINK-Os-NEXT: Running analysis: BranchProbabilityAnalysis
+; CHECK-POSTLINK-Oz-NEXT: Running analysis: BranchProbabilityAnalysis
 ; CHECK-POSTLINK-O-NEXT: Running pass: LoopLoadEliminationPass
 ; CHECK-POSTLINK-O-NEXT: Running analysis: LoopAccessAnalysis
 ; CHECK-POSTLINK-O-NEXT: Running pass: InstCombinePass