[SystemZ] Use LDE32 instead of LE, when Offset is small.

On z13, if eliminateFrameIndex() chooses LE (and not LEY), immediately
transform that LE to LDE32 to avoid partial register dependencies.

LEY should be generally preferred for big offsets over an expansion
into LAY + LDE32.

Reviewed by Ulrich Weigand.

llvm-svn: 266060

1 files changed, 7 insertions, 1 deletions

diff --git a/llvm/lib/Target/SystemZ/SystemZRegisterInfo.cpp b/llvm/lib/Target/SystemZ/SystemZRegisterInfo.cpp
index 6fd24e3df62..8d872b75d2e 100644
--- a/llvm/lib/Target/SystemZ/SystemZRegisterInfo.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZRegisterInfo.cpp
@@ -84,8 +84,14 @@ SystemZRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator MI,
   // accepts the offset exists.
   unsigned Opcode = MI->getOpcode();
   unsigned OpcodeForOffset = TII->getOpcodeForOffset(Opcode, Offset);
-  if (OpcodeForOffset)
+  if (OpcodeForOffset) {
+    if (OpcodeForOffset == SystemZ::LE &&
+        MF.getSubtarget<SystemZSubtarget>().hasVector()) {
+      // If LE is ok for offset, use LDE instead on z13.
+      OpcodeForOffset = SystemZ::LDE32;
+    }
     MI->getOperand(FIOperandNum).ChangeToRegister(BasePtr, false);
+  }
   else {
     // Create an anchor point that is in range.  Start at 0xffff so that
     // can use LLILH to load the immediate.