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

lib/Target/MSP430/MSP430ISelLowering.cpp

@@ -95,6 +95,8 @@ MSP430TargetLowering::MSP430TargetLowering(MSP430TargetMachine &tm) :
   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);

lib/Target/MSP430/MSP430RegisterInfo.cpp

@@ -328,7 +328,16 @@ void MSP430RegisterInfo::emitEpilogue(MachineFunction &MF,
   //  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) {

test/CodeGen/MSP430/2009-08-25-DynamicStackAlloc.ll

@@ -0,0 +1,30 @@
+; RUN: llvm-as < %s | llc
+; PR4769
+target datalayout = "e-p:16:8:8-i8:8:8-i16:8:8-i32:8:8"
+target triple = "msp430-generic-generic"
+
+define i16 @foo() nounwind readnone {
+entry:
+  %result = alloca i16, align 1                   ; <i16*> [#uses=2]
+  volatile store i16 0, i16* %result
+  %tmp = volatile load i16* %result               ; <i16> [#uses=1]
+  ret i16 %tmp
+}
+
+define i16 @main() nounwind {
+entry:
+  br label %while.cond
+
+while.cond:                                       ; preds = %while.cond, %entry
+  %call = call i16 @bar() nounwind                ; <i16> [#uses=1]
+  %tobool = icmp eq i16 %call, 0                  ; <i1> [#uses=1]
+  br i1 %tobool, label %while.end, label %while.cond
+
+while.end:                                        ; preds = %while.cond
+  %result.i = alloca i16, align 1                 ; <i16*> [#uses=2]
+  volatile store i16 0, i16* %result.i
+  %tmp.i = volatile load i16* %result.i           ; <i16> [#uses=0]
+  ret i16 0
+}
+
+declare i16 @bar()