Disable Subzero IR generation for performance testing.

tests_lit/reader_tests/phi.ll

 ; Test reading phi instructions.
 
 ; RUN: %p2i -i %s --insts | FileCheck %s
+; RUN: %if --need=allow_disable_ir_gen --command \
+; RUN:   %p2i -i %s --args -notranslate -timing -no-ir-gen \
+; RUN: | %if --need=allow_disable_ir_gen --command \
+; RUN:   FileCheck --check-prefix=NOIR %s
 
 ; TODO(kschimpf) Add forward reference examples.
 
 define internal i32 @testPhi1(i32 %arg) {
 entry:
   %cmp1 = icmp sgt i32 %arg, 0
   br i1 %cmp1, label %next, label %target
 next:
   br label %target
 target:
   %merge = phi i1 [ %cmp1, %entry ], [ false, %next ]
   %result = zext i1 %merge to i32
   ret i32 %result
 }
 
 ; CHECK:      define internal i32 @testPhi1(i32 %arg) {
 ; CHECK-NEXT: entry:
 ; CHECK-NEXT:   %cmp1 = icmp sgt i32 %arg, 0
 ; CHECK-NEXT:   br i1 %cmp1, label %next, label %target
 ; CHECK-NEXT: next:
 ; CHECK-NEXT:   br label %target
 ; CHECK-NEXT: target:
 ; CHECK-NEXT:   %merge = phi i1 [ %cmp1, %entry ], [ false, %next ]
 ; CHECK-NEXT:   %result = zext i1 %merge to i32
 ; CHECK-NEXT:   ret i32 %result
 ; CHECK-NEXT: }
 
+; NOIR: Total across all functions