[X86] mfence.ll - add COMMON prefix + replace X32 with X86 prefix

We try to only use X32 for gnux32 triple

Noticed while reviewing #106555

Author: RKSimon

llvm/test/CodeGen/X86/mfence.ll

@@ -1,30 +1,25 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: llc < %s -mtriple=i386-unknown-unknown -mattr=+sse2 | FileCheck %s --check-prefix=X32
-; RUN: llc < %s -mtriple=x86_64-unknown-unknown -mattr=-sse2 | FileCheck %s --check-prefix=X64
+; RUN: llc < %s -mtriple=i386-unknown-unknown -mattr=+sse2 | FileCheck %s --check-prefixes=CHECK,X86
+; RUN: llc < %s -mtriple=x86_64-unknown-unknown -mattr=-sse2 | FileCheck %s --check-prefixes=CHECK,X64
 
 ; It doesn't matter if an x86-64 target has specified "no-sse2"; we still can use mfence.
 
 define void @test() {
-; X32-LABEL: test:
-; X32:       # %bb.0:
-; X32-NEXT:    mfence
-; X32-NEXT:    retl
-;
-; X64-LABEL: test:
-; X64:       # %bb.0:
-; X64-NEXT:    mfence
-; X64-NEXT:    retq
+; CHECK-LABEL: test:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    mfence
+; CHECK-NEXT:    ret{{[l|q]}}
   fence seq_cst
   ret void
 }
 
 define i32 @fence(ptr %ptr) {
-; X32-LABEL: fence:
-; X32:       # %bb.0:
-; X32-NEXT:    movl {{[0-9]+}}(%esp), %eax
-; X32-NEXT:    mfence
-; X32-NEXT:    movl (%eax), %eax
-; X32-NEXT:    retl
+; X86-LABEL: fence:
+; X86:       # %bb.0:
+; X86-NEXT:    movl {{[0-9]+}}(%esp), %eax
+; X86-NEXT:    mfence
+; X86-NEXT:    movl (%eax), %eax
+; X86-NEXT:    retl
 ;
 ; X64-LABEL: fence:
 ; X64:       # %bb.0: