[ARM] Don't run the block placement pass at O0

The block placement pass shouldn't run unless optimisations are enabled.

Differential Revision: https://reviews.llvm.org/D94691

Author: SamTebbs33

llvm/lib/Target/ARM/ARMBlockPlacement.cpp

@@ -58,6 +58,8 @@ INITIALIZE_PASS(ARMBlockPlacement, DEBUG_TYPE, "ARM block placement", false,
                 false)
 
 bool ARMBlockPlacement::runOnMachineFunction(MachineFunction &MF) {
+  if (skipFunction(MF.getFunction()))
+      return false;
   const ARMSubtarget &ST = static_cast<const ARMSubtarget &>(MF.getSubtarget());
   if (!ST.hasLOB())
     return false;

llvm/lib/Target/ARM/ARMTargetMachine.cpp

@@ -553,11 +553,11 @@ void ARMPassConfig::addPreEmitPass() {
     return MF.getSubtarget<ARMSubtarget>().isThumb2();
   }));
 
-  addPass(createARMBlockPlacementPass());
-
-  // Don't optimize barriers at -O0.
-  if (getOptLevel() != CodeGenOpt::None)
+  // Don't optimize barriers or block placement at -O0.
+  if (getOptLevel() != CodeGenOpt::None) {
+    addPass(createARMBlockPlacementPass());
     addPass(createARMOptimizeBarriersPass());
+  }
 }
 
 void ARMPassConfig::addPreEmitPass2() {