use -filetype=null

Author: paperchalice

llvm/test/Analysis/DotMachineCFG/AMDGPU/functions.mir

@@ -1,6 +1,6 @@
 # RUN: llc -mtriple=amdgcn-- -run-pass=dot-machine-cfg  -mcfg-dot-filename-prefix=%t -mcfg-func-name=func2 -o -  %s 2>&1 > /dev/null
 # RUN: FileCheck %s -input-file=%t.func2.dot --check-prefix=MCFG
-# RUN: llc -mtriple=amdgcn-- -passes=dot-machine-cfg  -mcfg-dot-filename-prefix=%t -mcfg-func-name=func2 -o -  %s 2>&1 > /dev/null
+# RUN: llc -mtriple=amdgcn-- -passes=dot-machine-cfg  -mcfg-dot-filename-prefix=%t -mcfg-func-name=func2 -filetype=null %s
 # RUN: FileCheck %s -input-file=%t.func2.dot --check-prefix=MCFG
 
 # MCFG-NOT: digraph "Machine CFG for 'func1' function"

llvm/test/Analysis/DotMachineCFG/AMDGPU/irreducible.mir

@@ -2,9 +2,9 @@
 # RUN: FileCheck %s -input-file=%t.irreducible.dot --check-prefix=MCFG
 # RUN: llc -mtriple=amdgcn-- -run-pass=dot-machine-cfg  -mcfg-dot-filename-prefix=%t -dot-mcfg-only -o -  %s 2>&1 > /dev/null
 # RUN: FileCheck %s -input-file=%t.irreducible.dot --check-prefix=MCFG-ONLY
-# RUN: llc -mtriple=amdgcn-- -passes=dot-machine-cfg  -mcfg-dot-filename-prefix=%t -o -  %s 2>&1 > /dev/null
+# RUN: llc -mtriple=amdgcn-- -passes=dot-machine-cfg  -mcfg-dot-filename-prefix=%t -filetype=null %s
 # RUN: FileCheck %s -input-file=%t.irreducible.dot --check-prefix=MCFG
-# RUN: llc -mtriple=amdgcn-- -passes=dot-machine-cfg  -mcfg-dot-filename-prefix=%t -dot-mcfg-only -o -  %s 2>&1 > /dev/null
+# RUN: llc -mtriple=amdgcn-- -passes=dot-machine-cfg  -mcfg-dot-filename-prefix=%t -dot-mcfg-only -filetype=null %s
 # RUN: FileCheck %s -input-file=%t.irreducible.dot --check-prefix=MCFG-ONLY
 
 # MCFG: digraph "Machine CFG for 'irreducible' function"