[X86] Move target-generic code into CodeGen [NFC]

This code is the same for all platforms.

Differential Revision: https://reviews.llvm.org/D124566

1 files changed, 26 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/PrologEpilogInserter.cpp b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
index bc45450..f222b4a 100644
--- a/llvm/lib/CodeGen/PrologEpilogInserter.cpp
+++ b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
@@ -1227,7 +1227,7 @@ void PEI::insertZeroCallUsedRegs(MachineFunction &MF) {
     RegsToZero.set(Reg);
   }
 
-  // Remove registers that are live when leaving the function.
+  // Don't clear registers that are live when leaving the function.
   for (const MachineBasicBlock &MBB : MF)
     for (const MachineInstr &MI : MBB.terminators()) {
       if (!MI.isReturn())
@@ -1242,6 +1242,31 @@ void PEI::insertZeroCallUsedRegs(MachineFunction &MF) {
       }
     }
 
+  // Don't need to clear registers that are used/clobbered by terminating
+  // instructions.
+  for (const MachineBasicBlock &MBB : MF) {
+    if (!MBB.isReturnBlock())
+      continue;
+
+    MachineBasicBlock::const_iterator MBBI = MBB.getFirstTerminator();
+    for (MachineBasicBlock::const_iterator I = MBBI, E = MBB.end(); I != E;
+         ++I) {
+      for (const MachineOperand &MO : I->operands()) {
+        if (!MO.isReg())
+          continue;
+
+        for (const MCPhysReg &Reg :
+             TRI.sub_and_superregs_inclusive(MO.getReg()))
+          RegsToZero.reset(Reg);
+      }
+    }
+  }
+
+  // Don't clear registers that are reset before exiting.
+  for (const CalleeSavedInfo &CSI : MF.getFrameInfo().getCalleeSavedInfo())
+    for (MCRegister Reg : TRI.sub_and_superregs_inclusive(CSI.getReg()))
+      RegsToZero.reset(Reg);
+
   const TargetFrameLowering &TFI = *MF.getSubtarget().getFrameLowering();
   for (MachineBasicBlock &MBB : MF)
     if (MBB.isReturnBlock())