ARC: Enforce function alignment at code emission time

Don't do this in the MachineFunctionInfo constructor. Also, ensure the
alignment rather than overwriting it outright. I vaguely remember
there was another place to enforce the target minimum alignment, but I
couldn't find it (it's there for instructions).

llvm/lib/Target/ARC/ARCAsmPrinter.cpp

@@ -42,6 +42,8 @@ public:
 
   StringRef getPassName() const override { return "ARC Assembly Printer"; }
   void emitInstruction(const MachineInstr *MI) override;
+
+  bool runOnMachineFunction(MachineFunction &MF) override;
 };
 
 } // end anonymous namespace
@@ -61,6 +63,12 @@ void ARCAsmPrinter::emitInstruction(const MachineInstr *MI) {
   EmitToStreamer(*OutStreamer, TmpInst);
 }
 
+bool ARCAsmPrinter::runOnMachineFunction(MachineFunction &MF) {
+  // Functions are 4-byte aligned.
+  MF.ensureAlignment(Align(4));
+  AsmPrinter::runOnMachineFunction(MF);
+}
+
 // Force static initialization.
 extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeARCAsmPrinter() {
   RegisterAsmPrinter<ARCAsmPrinter> X(getTheARCTarget());

llvm/lib/Target/ARC/ARCMachineFunctionInfo.h

@@ -33,10 +33,7 @@ public:
 
   explicit ARCFunctionInfo(MachineFunction &MF)
       : ReturnStackOffsetSet(false), VarArgsFrameIndex(0),
-        ReturnStackOffset(-1U), MaxCallStackReq(0) {
-    // Functions are 4-byte aligned.
-    MF.setAlignment(Align(4));
-  }
+        ReturnStackOffset(-1U), MaxCallStackReq(0) {}
 
   ~ARCFunctionInfo() {}