[XCore] Support functions returning more than 4 words.

Summary:
If a function returns a large struct by value return the first 4 words
in registers and the rest on the stack in a location reserved by the
caller. This is needed to support the xC language which supports
functions returning an arbitrary number of return values.

Reviewers: robertlytton

Reviewed By: robertlytton

CC: llvm-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D2889

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202397 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/XCore/XCoreISelLowering.h

@@ -42,6 +42,9 @@ namespace llvm {
       // cp relative address
       CPRelativeWrapper,
 
+      // Load word from stack
+      LDWSP,
+
       // Store word to stack
       STWSP,