[LoongArch][MC] Pre-commit tests for instr bl fixupkind testing (#72826)

This patch is used to test whether fixupkind for bl can be returned
correctly. When BL has target-flags(loongarch-call), there is no error.
But without this flag, an assertion error will appear. So the test is
just tagged as "Expectedly Failed" now until the following patch fix it.

(cherry picked from commit 2ca028c)

Author: zhaoqi5

llvm/test/CodeGen/LoongArch/test_bl_fixupkind.mir

@@ -0,0 +1,66 @@
+## Tagged as "Expectedly Failed" until the following patch fix it
+# XFAIL: *
+# RUN: llc --mtriple=loongarch64 --filetype=obj %s -o - | \
+# RUN: llvm-objdump -d - | FileCheck %s
+
+# REQUIRES: asserts
+
+## Check that bl can get fixupkind correctly.
+## When BL has target-flags(loongarch-call), there is no error. But without
+## this flag, an assertion error will appear:
+## Assertion `FixupKind != LoongArch::fixup_loongarch_invalid && "Unhandled expression!"' failed.
+
+--- |
+  target datalayout = "e-m:e-p:64:64-i64:64-i128:128-n64-S128"
+  target triple = "loongarch64"
+  
+  define dso_local void @test_bl_fixupkind_with_flag() {
+  ; CHECK-LABEL: test_bl_fixupkind_with_flag
+  ; CHECK:         addi.d $sp, $sp, -16
+  ; CHECK-NEXT:    st.d $ra, $sp, 8
+  ; CHECK-NEXT:    bl 0 <test_bl_fixupkind_with_flag+0x8>
+  ; CHECK-NEXT:    ld.d $ra, $sp, 8
+  ; CHECK-NEXT:    addi.d $sp, $sp, 16
+  ; CHECK-NEXT:    ret
+  entry:
+    call void @foo()
+    ret void
+  }
+  
+  define dso_local void @test_bl_fixupkind_without_flag() {
+  ; CHECK-LABEL: test_bl_fixupkind_without_flag
+  ; CHECK:         addi.d $sp, $sp, -16
+  ; CHECK-NEXT:    st.d $ra, $sp, 8
+  ; CHECK-NEXT:    bl 0 <test_bl_fixupkind_without_flag+0x8>
+  ; CHECK-NEXT:    ld.d $ra, $sp, 8
+  ; CHECK-NEXT:    addi.d $sp, $sp, 16
+  ; CHECK-NEXT:    ret
+  entry:
+    call void @foo()
+    ret void
+  }
+  
+  declare dso_local void @foo(...)
+...
+---
+name:            test_bl_fixupkind_with_flag
+tracksRegLiveness: true
+body:             |
+  bb.0.entry:
+    ADJCALLSTACKDOWN 0, 0, implicit-def dead $r3, implicit $r3
+    BL target-flags(loongarch-call) @foo, csr_ilp32d_lp64d, implicit-def $r1, implicit-def dead $r1, implicit-def $r3
+    ADJCALLSTACKUP 0, 0, implicit-def dead $r3, implicit $r3
+    PseudoRET
+
+...
+---
+name:            test_bl_fixupkind_without_flag
+tracksRegLiveness: true
+body:             |
+  bb.0.entry:
+    ADJCALLSTACKDOWN 0, 0, implicit-def dead $r3, implicit $r3
+    BL @foo, csr_ilp32d_lp64d, implicit-def $r1, implicit-def dead $r1, implicit-def $r3
+    ADJCALLSTACKUP 0, 0, implicit-def dead $r3, implicit $r3
+    PseudoRET
+
+...