[SystemZ] Handle address clobbering in splitMove().

llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp

@@ -70,49 +70,62 @@ void SystemZInstrInfo::splitMove(MachineBasicBlock::iterator MI,
   MachineBasicBlock *MBB = MI->getParent();
   MachineFunction &MF = *MBB->getParent();
 
-  // Get two load or store instructions.  Use the original instruction for one
-  // of them (arbitrarily the second here) and create a clone for the other.
-  MachineInstr *EarlierMI = MF.CloneMachineInstr(&*MI);
-  MBB->insert(MI, EarlierMI);
+  // Get two load or store instructions.  Use the original instruction for
+  // one of them and create a clone for the other.
+  MachineInstr *HighPartMI = MF.CloneMachineInstr(&*MI);
+  MachineInstr *LowPartMI = &*MI;
+  MBB->insert(LowPartMI, HighPartMI);
 
   // Set up the two 64-bit registers and remember super reg and its flags.
-  MachineOperand &HighRegOp = EarlierMI->getOperand(0);
-  MachineOperand &LowRegOp = MI->getOperand(0);
+  MachineOperand &HighRegOp = HighPartMI->getOperand(0);
+  MachineOperand &LowRegOp = LowPartMI->getOperand(0);
   Register Reg128 = LowRegOp.getReg();
   unsigned Reg128Killed = getKillRegState(LowRegOp.isKill());
   unsigned Reg128Undef  = getUndefRegState(LowRegOp.isUndef());
   HighRegOp.setReg(RI.getSubReg(HighRegOp.getReg(), SystemZ::subreg_h64));
   LowRegOp.setReg(RI.getSubReg(LowRegOp.getReg(), SystemZ::subreg_l64));
 
-  if (MI->mayStore()) {
-    // Add implicit uses of the super register in case one of the subregs is
-    // undefined. We could track liveness and skip storing an undefined
-    // subreg, but this is hopefully rare (discovered with llvm-stress).
-    // If Reg128 was killed, set kill flag on MI.
-    unsigned Reg128UndefImpl = (Reg128Undef | RegState::Implicit);
-    MachineInstrBuilder(MF, EarlierMI).addReg(Reg128, Reg128UndefImpl);
-    MachineInstrBuilder(MF, MI).addReg(Reg128, (Reg128UndefImpl | Reg128Killed));
-  }
-
   // The address in the first (high) instruction is already correct.
   // Adjust the offset in the second (low) instruction.
-  MachineOperand &HighOffsetOp = EarlierMI->getOperand(2);
-  MachineOperand &LowOffsetOp = MI->getOperand(2);
+  MachineOperand &HighOffsetOp = HighPartMI->getOperand(2);
+  MachineOperand &LowOffsetOp = LowPartMI->getOperand(2);
   LowOffsetOp.setImm(LowOffsetOp.getImm() + 8);
 
-  // Clear the kill flags on the registers in the first instruction.
-  if (EarlierMI->getOperand(0).isReg() && EarlierMI->getOperand(0).isUse())
-    EarlierMI->getOperand(0).setIsKill(false);
-  EarlierMI->getOperand(1).setIsKill(false);
-  EarlierMI->getOperand(3).setIsKill(false);
-
   // Set the opcodes.
   unsigned HighOpcode = getOpcodeForOffset(NewOpcode, HighOffsetOp.getImm());
   unsigned LowOpcode = getOpcodeForOffset(NewOpcode, LowOffsetOp.getImm());
   assert(HighOpcode && LowOpcode && "Both offsets should be in range");
+  HighPartMI->setDesc(get(HighOpcode));
+  LowPartMI->setDesc(get(LowOpcode));
+
+  MachineInstr *FirstMI = HighPartMI;
+  if (MI->mayStore()) {
+    FirstMI->getOperand(0).setIsKill(false);
+    // Add implicit uses of the super register in case one of the subregs is
+    // undefined. We could track liveness and skip storing an undefined
+    // subreg, but this is hopefully rare (discovered with llvm-stress).
+    // If Reg128 was killed, set kill flag on MI.
+    unsigned Reg128UndefImpl = (Reg128Undef | RegState::Implicit);
+    MachineInstrBuilder(MF, HighPartMI).addReg(Reg128, Reg128UndefImpl);
+    MachineInstrBuilder(MF, LowPartMI).addReg(Reg128, (Reg128UndefImpl | Reg128Killed));
+  } else {
+    // If HighPartMI clobbers any of the address registers, it needs to come
+    // after LowPartMI.
+    auto overlapsAddressReg = [&](Register Reg) -> bool {
+      return RI.regsOverlap(Reg, MI->getOperand(1).getReg()) ||
+             RI.regsOverlap(Reg, MI->getOperand(3).getReg());
+    };
+    if (overlapsAddressReg(HighRegOp.getReg())) {
+      assert(!overlapsAddressReg(LowRegOp.getReg()) &&
+             "Both loads clobber address!");
+      MBB->splice(HighPartMI, MBB, LowPartMI);
+      FirstMI = LowPartMI;
+    }
+  }
 
-  EarlierMI->setDesc(get(HighOpcode));
-  MI->setDesc(get(LowOpcode));
+  // Clear the kill flags on the address registers in the first instruction.
+  FirstMI->getOperand(1).setIsKill(false);
+  FirstMI->getOperand(3).setIsKill(false);
 }
 
 // Split ADJDYNALLOC instruction MI.

llvm/test/CodeGen/SystemZ/splitMove_addressReg.mir

@@ -0,0 +1,26 @@
+# RUN: llc -mtriple=s390x-linux-gnu -run-pass=postrapseudos \
+# RUN:   %s -o - -verify-machineinstrs | FileCheck %s
+#
+# Test that a L128 reload do not overwrite an address register prematurely
+# after being split into two LGs.
+
+--- |
+  target triple = "s390x-unknown-unknown"
+
+  define void @fun() {
+    ret void
+  }
+
+...
+
+# CHECK: name: fun
+
+---
+name:            'fun'
+body:             |
+  bb.0:
+    liveins: $r4d, $r15d
+    $r4q = L128 $r15d, 14920, killed $r4d
+    Return
+
+...