Allow KILL MI with dangling MMO in MachineVerifier.

Author: JonPsson1

llvm/lib/CodeGen/MachineVerifier.cpp

@@ -2271,7 +2271,7 @@ void MachineVerifier::visitMachineInstrBefore(const MachineInstr *MI) {
 
   // Check the MachineMemOperands for basic consistency.
   for (MachineMemOperand *Op : MI->memoperands()) {
-    if (Op->isLoad() && !MI->mayLoad())
+    if (Op->isLoad() && (!MI->mayLoad() && !MI->isKill()))
       report("Missing mayLoad flag", MI);
     if (Op->isStore() && !MI->mayStore())
       report("Missing mayStore flag", MI);

llvm/test/CodeGen/SystemZ/machine-ver-kill-memop.ll

@@ -0,0 +1,30 @@
+; RUN: llc < %s -mtriple=s390x-linux-gnu -mcpu=z16 -disable-machine-dce \
+; RUN:   -verify-machineinstrs -O3
+;
+; Test that this passes the verifier even though a KILL instruction with a
+; dangling memory operand emerges.
+
+define void @fun(ptr %Src, ptr %Dst) {
+  br label %2
+
+2:
+  %3 = load i32, ptr %Src, align 4
+  %4 = freeze i32 %3
+  %5 = icmp eq i32 %4, 0
+  %6 = load i32, ptr poison, align 4
+  %7 = select i1 %5, i32 0, i32 %6
+  %8 = load i32, ptr %Src, align 4
+  %9 = freeze i32 %8
+  %10 = icmp eq i32 %9, 0
+  %11 = load i32, ptr poison, align 4
+  %12 = select i1 %10, i32 0, i32 %11
+  br label %13
+
+13:
+  %14 = phi i32 [ %12, %13 ], [ %7, %2 ]
+  %15 = icmp slt i32 %14, 5
+  %16 = zext i1 %15 to i64
+  %17 = xor i64 poison, %16
+  store i64 %17, ptr %Dst, align 8
+  br label %13
+}