[InstCombine] auto-generate test CHECK lines; NFC

The check line was not enabled until bfb1559,
and then it was excessive, so the test started failing.

llvm/test/Transforms/InstCombine/2008-01-06-VoidCast.ll

@@ -1,12 +1,20 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature
 ; RUN: opt < %s -passes=instcombine -S | FileCheck %s
 
 define void @f(i16 %y) {
+; CHECK-LABEL: define {{[^@]+}}@f
+; CHECK-SAME: (i16 [[Y:%.*]]) {
+; CHECK-NEXT:    ret void
+;
   ret void
 }
 
 define i32 @g(i32 %y) {
-; CHECK-LABEL: @g(
-; CHECK-NEXT: %x = call i32 @f(i32 %y)		; <i32> [#uses=1]
-  %x = call i32 @f( i32 %y )		; <i32> [#uses=1]
+; CHECK-LABEL: define {{[^@]+}}@g
+; CHECK-SAME: (i32 [[Y:%.*]]) {
+; CHECK-NEXT:    [[X:%.*]] = call i32 @f(i32 [[Y]])
+; CHECK-NEXT:    ret i32 [[X]]
+;
+  %x = call i32 @f( i32 %y )
   ret i32 %x
 }