[SystemZ] Allocate a second register scavenging slot

This is another prerequisite for frame-to-frame MVC copies.
I'll commit the patch that makes use of the slot separately.

The downside of trying to test many corner cases with each of the
available addressing modes is that a fair few tests need to account
for the new frame layout.  I do still think it's useful to have all
these tests though, since it's something that wouldn't get much coverage
otherwise.

llvm-svn: 185698

1 files changed, 6 insertions, 2 deletions

diff --git a/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp b/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
index 3ae59782f60..a58da901720 100644
--- a/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
@@ -270,10 +270,14 @@ processFunctionBeforeFrameFinalized(MachineFunction &MF,
   MachineFrameInfo *MFFrame = MF.getFrameInfo();
   uint64_t MaxReach = (MFFrame->estimateStackSize(MF) +
                        SystemZMC::CallFrameSize * 2);
-  if (!isUInt<12>(MaxReach))
-    // We may need a register scavenging slot if some parts of the frame
+  if (!isUInt<12>(MaxReach)) {
+    // We may need register scavenging slots if some parts of the frame
     // are outside the reach of an unsigned 12-bit displacement.
+    // Create 2 for the case where both addresses in an MVC are
+    // out of range.
     RS->addScavengingFrameIndex(MFFrame->CreateStackObject(8, 8, false));
+    RS->addScavengingFrameIndex(MFFrame->CreateStackObject(8, 8, false));
+  }
 }
 
 // Emit instructions before MBBI (in MBB) to add NumBytes to Reg.