[X86] Add test case for PR43758. NFC

test/CodeGen/X86/leaFixup64.mir

@@ -148,6 +148,10 @@
     ret i32 0
   }
 
+  define i32 @pr43758() {
+    ret i32 0
+  }
+
 
 ...
 ---
@@ -1129,6 +1133,62 @@ body:             |
     RETQ $ebp
 
 ...
+---
+name:            pr43758
+alignment:       16
+exposesReturnsTwice: false
+legalized:       false
+regBankSelected: false
+selected:        false
+tracksRegLiveness: true
+liveins:
+  - { reg: '$rax' }
+  - { reg: '$rbp' }
+frameInfo:
+  isFrameAddressTaken: false
+  isReturnAddressTaken: false
+  hasStackMap:     false
+  hasPatchPoint:   false
+  stackSize:       0
+  offsetAdjustment: 0
+  maxAlignment:    0
+  adjustsStack:    false
+  hasCalls:        false
+  maxCallFrameSize: 0
+  hasOpaqueSPAdjustment: false
+  hasVAStart:      false
+  hasMustTailInVarArgFunc: false
+body:             |
+  bb.0 (%ir-block.0):
+    liveins: $rax, $rbp
+
+    ; CHECK-LABEL: name: pr43758
+    ; CHECK: liveins: $rax, $rbp
+    ; CHECK: DBG_VALUE 0, $noreg
+    ; CHECK: NOOP
+    ; CHECK: NOOP
+    ; CHECK: NOOP
+    ; CHECK: NOOP
+    ; CHECK: $ebp = LEA64_32r killed $rbp, 1, killed $rax, 0, $noreg
+    ; CHECK: NOOP
+    ; CHECK: NOOP
+    ; CHECK: NOOP
+    ; CHECK: NOOP
+    ; CHECK: RETQ $ebp
+    DBG_VALUE 0, $noreg
+    NOOP
+    NOOP
+    NOOP
+    NOOP
+    $ebp = LEA64_32r killed $rbp, 1, killed $rax, 0, $noreg
+    NOOP
+    NOOP
+    NOOP
+    NOOP
+    RETQ $ebp
+
+...
+...