Disable Subzero IR generation for performance testing.

This CL allows one to time Subzero's bitcode parsing without IR generation
(other than types, function declarations, and uninitialized global variables)
for performance testing.

BUG=None
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/696383004
diff --git a/tests_lit/reader_tests/phi.ll b/tests_lit/reader_tests/phi.ll
index 3799d4b..a90bc4c 100644
--- a/tests_lit/reader_tests/phi.ll
+++ b/tests_lit/reader_tests/phi.ll
@@ -1,6 +1,10 @@
 ; 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.
 
@@ -28,3 +32,4 @@
 ; CHECK-NEXT:   ret i32 %result
 ; CHECK-NEXT: }
 
+; NOIR: Total across all functions