Provide dynamic_stackalloc lowering for MSP430.
This fixes PR4769

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@80001 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/MSP430/MSP430ISelLowering.cpp b/lib/Target/MSP430/MSP430ISelLowering.cpp
index ec19c38..3e6169e 100644
--- a/lib/Target/MSP430/MSP430ISelLowering.cpp
+++ b/lib/Target/MSP430/MSP430ISelLowering.cpp
@@ -95,6 +95,8 @@
   setOperationAction(ISD::SELECT_CC,        MVT::i8,    Custom);
   setOperationAction(ISD::SELECT_CC,        MVT::i16,   Custom);
   setOperationAction(ISD::SIGN_EXTEND,      MVT::i16,   Custom);
+  setOperationAction(ISD::DYNAMIC_STACKALLOC, MVT::i8, Expand);
+  setOperationAction(ISD::DYNAMIC_STACKALLOC, MVT::i16, Expand);
 
   setOperationAction(ISD::CTTZ,             MVT::i8,    Expand);
   setOperationAction(ISD::CTTZ,             MVT::i16,   Expand);
diff --git a/lib/Target/MSP430/MSP430RegisterInfo.cpp b/lib/Target/MSP430/MSP430RegisterInfo.cpp
index d1401f5..72994eb 100644
--- a/lib/Target/MSP430/MSP430RegisterInfo.cpp
+++ b/lib/Target/MSP430/MSP430RegisterInfo.cpp
@@ -328,7 +328,16 @@
   //  mergeSPUpdatesUp(MBB, MBBI, StackPtr, &NumBytes);
 
   if (MFI->hasVarSizedObjects()) {
-    llvm_unreachable("Not implemented yet!");
+    BuildMI(MBB, MBBI, DL,
+            TII.get(MSP430::MOV16rr), MSP430::SPW).addReg(MSP430::FPW);
+    if (CSSize) {
+      MachineInstr *MI =
+        BuildMI(MBB, MBBI, DL,
+                TII.get(MSP430::SUB16ri), MSP430::SPW)
+        .addReg(MSP430::SPW).addImm(CSSize);
+      // The SRW implicit def is dead.
+      MI->getOperand(3).setIsDead();
+    }
   } else {
     // adjust stack pointer back: SPW += numbytes
     if (NumBytes) {