[LoongArch] Transfer MI flags when expand PseudoCALL

[wangleiat]

Summary

When expanding a PseudoCALL, the corresponding flags (e.g. nomerge)
need to be passed to the new instruction.

This patch also adds test for the nomerge attribute.

The nomerge attribute was added during LowerCall, but was lost
during expand PseudoCALL. Now add it back.

llvm/lib/Target/LoongArch/LoongArchExpandPseudoInsts.cpp

case CodeModel::Medium: {
     CALL.addGlobalAddress(GV, 0, LoongArchII::MO_PCREL_LO);
     break;
   }
   }
 
   // Transfer implicit operands.
   CALL.copyImplicitOps(MI);
 
+  // Transfer MI flags.
+  CALL.setMIFlags(MI.getFlags());
+
   MI.eraseFromParent();
   return true;
 }
 
 } // end namespace
 
 INITIALIZE_PASS(LoongArchPreRAExpandPseudo, "loongarch-prera-expand-pseudo",
                 LOONGARCH_PRERA_EXPAND_PSEUDO_NAME, false, false)
 
 namespace llvm {
 
 FunctionPass *createLoongArchPreRAExpandPseudoPass() {
   return new LoongArchPreRAExpandPseudo();
 }
 
 } // end namespace llvm

llvm/test/CodeGen/LoongArch/nomerge.ll

+; RUN: llc --mtriple=loongarch64 < %s | FileCheck %s
+
+define void @foo(i32 %i) {
+entry:
+  switch i32 %i, label %if.end3 [
+    i32 5, label %if.then
+    i32 7, label %if.then2
+  ]
+
+if.then:
+  tail call void @bar() #0
+  br label %if.end3
+
+if.then2:
+  tail call void @bar() #0
+  br label %if.end3
+
+if.end3:
+  tail call void @bar() #0
+  ret void
+}
+
+declare void @bar()
+
+attributes #0 = { nomerge }
+
+; CHECK-LABEL: foo:
+; CHECK: # %bb.0: # %entry
+; CHECK: # %bb.1: # %entry
+; CHECK: # %bb.2: # %if.then
+; CHECK-NEXT: bl %plt(bar)
+; CHECK: .LBB0_3: # %if.then2
+; CHECK-NEXT: bl %plt(bar)
+; CHECK: .LBB0_4: # %if.end3
+; CHECK: bl %plt(bar)