diff --git a/llvm/utils/lit/lit/builtin_commands/diff.py b/llvm/utils/lit/lit/builtin_commands/diff.py
--- a/llvm/utils/lit/lit/builtin_commands/diff.py
+++ b/llvm/utils/lit/lit/builtin_commands/diff.py
@@ -89,7 +89,8 @@
     if flags.strip_trailing_cr:
         f = compose2(lambda line: line.replace('\r\n', '\n'), f)
     if flags.ignore_all_space or flags.ignore_space_change:
-        ignoreSpace = lambda line, separator: separator.join(line.split())
+        ignoreSpace = lambda line, separator: \
+                          separator.join(line.split()) + "\n"
         ignoreAllSpaceOrSpaceChange = functools.partial(ignoreSpace, separator='' if flags.ignore_all_space else ' ')
         f = compose2(ignoreAllSpaceOrSpaceChange, f)
 
diff --git a/llvm/utils/lit/tests/Inputs/shtest-shell/diff-b.txt b/llvm/utils/lit/tests/Inputs/shtest-shell/diff-b.txt
new file mode 100644
--- /dev/null
+++ b/llvm/utils/lit/tests/Inputs/shtest-shell/diff-b.txt
@@ -0,0 +1,8 @@
+# RUN: echo 'f o o' > %t.0
+# RUN: echo 'b a r' >> %t.0
+
+# RUN: echo 'f  o  o' > %t.1
+# RUN: echo 'bar' >> %t.1
+
+# Due to -b, only second line has a change.
+# RUN: diff -b %t.0 %t.1
diff --git a/llvm/utils/lit/tests/Inputs/shtest-shell/diff-w.txt b/llvm/utils/lit/tests/Inputs/shtest-shell/diff-w.txt
new file mode 100644
--- /dev/null
+++ b/llvm/utils/lit/tests/Inputs/shtest-shell/diff-w.txt
@@ -0,0 +1,10 @@
+# RUN: echo 'f o o' > %t.0
+# RUN: echo 'b a r' >> %t.0
+# RUN: echo 'b a z' >> %t.0
+
+# RUN: echo 'f  o  o' > %t.1
+# RUN: echo 'bar' >> %t.1
+# RUN: echo 'b a t' >> %t.1
+
+# Due to -w, only third line has a change.
+# RUN: diff -w %t.0 %t.1
diff --git a/llvm/utils/lit/tests/max-failures.py b/llvm/utils/lit/tests/max-failures.py
--- a/llvm/utils/lit/tests/max-failures.py
+++ b/llvm/utils/lit/tests/max-failures.py
@@ -8,7 +8,7 @@
 #
 # END.
 
-# CHECK: Failing Tests (33)
+# CHECK: Failing Tests (35)
 # CHECK: Failing Tests (1)
 # CHECK: Failing Tests (2)
 # CHECK: error: argument --max-failures: requires positive integer, but found '0'
diff --git a/llvm/utils/lit/tests/shtest-shell.py b/llvm/utils/lit/tests/shtest-shell.py
--- a/llvm/utils/lit/tests/shtest-shell.py
+++ b/llvm/utils/lit/tests/shtest-shell.py
@@ -34,6 +34,22 @@
 # CHECK: error: command failed with exit status: 127
 # CHECK: ***
 
+# CHECK: PASS: shtest-shell :: dev-null.txt
+
+# CHECK: FAIL: shtest-shell :: diff-b.txt
+# CHECK: *** TEST 'shtest-shell :: diff-b.txt' FAILED ***
+# CHECK: $ "diff" "-b" "{{[^"]*}}.0" "{{[^"]*}}.1"
+# CHECK: # command output:
+# CHECK: 1,2
+# CHECK-NEXT: {{^  }}f o o
+# CHECK-NEXT: ! b a r
+# CHECK-NEXT: ---
+# CHECK-NEXT: {{^  }}f o o
+# CHECK-NEXT: ! bar
+# CHECK-EMPTY:
+# CHECK: error: command failed with exit status: 1
+# CHECK: ***
+
 
 # CHECK: FAIL: shtest-shell :: diff-encodings.txt
 # CHECK: *** TEST 'shtest-shell :: diff-encodings.txt' FAILED ***
@@ -460,6 +476,22 @@
 # CHECK: ***
 
 
+# CHECK: FAIL: shtest-shell :: diff-w.txt
+# CHECK: *** TEST 'shtest-shell :: diff-w.txt' FAILED ***
+# CHECK: $ "diff" "-w" "{{[^"]*}}.0" "{{[^"]*}}.1"
+# CHECK: # command output:
+# CHECK: 1,3
+# CHECK-NEXT: {{^  }}foo
+# CHECK-NEXT: {{^  }}bar
+# CHECK-NEXT: ! baz
+# CHECK-NEXT: ---
+# CHECK-NEXT: {{^  }}foo
+# CHECK-NEXT: {{^  }}bar
+# CHECK-NEXT: ! bat
+# CHECK-EMPTY:
+# CHECK: error: command failed with exit status: 1
+# CHECK: ***
+
 # CHECK: FAIL: shtest-shell :: error-0.txt
 # CHECK: *** TEST 'shtest-shell :: error-0.txt' FAILED ***
 # CHECK: $ "not-a-real-command"
@@ -551,4 +583,4 @@
 # CHECK: ***
 
 # CHECK: PASS: shtest-shell :: valid-shell.txt
-# CHECK: Failing Tests (33)
+# CHECK: Failing Tests (35)