[PowerPC] Remove redundant TOC saves

This patch adds a peep hole optimization to remove any redundant toc save
instructions added as part of the call sequence for indirect calls. It removes
any toc saves within a function that are dominated by another toc save.

Differential Revision: https://reviews.llvm.org/D39736

llvm-svn: 319087

1 files changed, 14 insertions, 0 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp b/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
index 99a52902a52..f25b929c808 100644
--- a/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
+++ b/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
@@ -2266,6 +2266,20 @@ static bool isZeroExtendingOp(const MachineInstr &MI) {
   return false;
 }
 
+// This function returns true if the input MachineInstr is a TOC save
+// instruction.
+bool PPCInstrInfo::isTOCSaveMI(const MachineInstr &MI) const {
+  if (!MI.getOperand(1).isImm() || !MI.getOperand(2).isReg())
+    return false;
+  unsigned TOCSaveOffset = Subtarget.getFrameLowering()->getTOCSaveOffset();
+  unsigned StackOffset = MI.getOperand(1).getImm();
+  unsigned StackReg = MI.getOperand(2).getReg();
+  if (StackReg == PPC::X1 && StackOffset == TOCSaveOffset)
+    return true;
+
+  return false;
+}
+
 // We limit the max depth to track incoming values of PHIs or binary ops
 // (e.g. AND) to avoid exsessive cost.
 const unsigned MAX_DEPTH = 1;