[Mips] Add FileCheck to a test that just tested for a crash.

I believe the generated code here can suffer from double rounding.
So I wanted to capture the existing codegen so we can make
decisions about how to fix it.

llvm/test/CodeGen/Mips/uitofp.ll

@@ -1,6 +1,25 @@
-; RUN: llc -march=mips -mattr=+single-float < %s
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -march=mips -mattr=+single-float < %s | FileCheck %s
 
 define void @f0() nounwind {
+; CHECK-LABEL: f0:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    addiu $sp, $sp, -8
+; CHECK-NEXT:    addiu $1, $zero, 1
+; CHECK-NEXT:    sw $1, 4($sp)
+; CHECK-NEXT:    lui $1, %hi($CPI0_0)
+; CHECK-NEXT:    addiu $1, $1, %lo($CPI0_0)
+; CHECK-NEXT:    lw $2, 4($sp)
+; CHECK-NEXT:    srl $3, $2, 29
+; CHECK-NEXT:    andi $3, $3, 4
+; CHECK-NEXT:    addu $1, $1, $3
+; CHECK-NEXT:    lwc1 $f0, 0($1)
+; CHECK-NEXT:    mtc1 $2, $f1
+; CHECK-NEXT:    cvt.s.w $f1, $f1
+; CHECK-NEXT:    add.s $f0, $f1, $f0
+; CHECK-NEXT:    swc1 $f0, 0($sp)
+; CHECK-NEXT:    jr $ra
+; CHECK-NEXT:    addiu $sp, $sp, 8
 entry:
   %b = alloca i32, align 4
   %a = alloca float, align 4