diff --git a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
--- a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
@@ -307,6 +307,11 @@
                   cl::desc("Enable KernelMemorySanitizer instrumentation"),
                   cl::Hidden, cl::init(false));
 
+static cl::opt<bool>
+    ClNoSanitizeWholeFile("msan-no-sanitize-all",
+                          cl::desc("Apply no_sanitize to the whole file"),
+                          cl::Hidden, cl::init(false));
+
 // This is an experiment to enable handling of cases where shadow is a non-zero
 // compile-time constant. For some unexplainable reason they were silently
 // ignored in the instrumentation.
@@ -1095,7 +1100,8 @@
   MemorySanitizerVisitor(Function &F, MemorySanitizer &MS,
                          const TargetLibraryInfo &TLI)
       : F(F), MS(MS), VAHelper(CreateVarArgHelper(F, MS, *this)), TLI(&TLI) {
-    bool SanitizeFunction = F.hasFnAttribute(Attribute::SanitizeMemory);
+    bool SanitizeFunction =
+        F.hasFnAttribute(Attribute::SanitizeMemory) && !ClNoSanitizeWholeFile;
     InsertChecks = SanitizeFunction;
     PropagateShadow = SanitizeFunction;
     PoisonStack = SanitizeFunction && ClPoisonStack;
diff --git a/llvm/test/Instrumentation/MemorySanitizer/msan-no-sanitize-all.ll b/llvm/test/Instrumentation/MemorySanitizer/msan-no-sanitize-all.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Instrumentation/MemorySanitizer/msan-no-sanitize-all.ll
@@ -0,0 +1,49 @@
+; Test for -msan-no-sanitize-all, which should treat every function in the file
+; as if it didn't have the sanitize_memory attribute.
+; RUN: opt < %s -msan-check-access-address=0 -S -passes='module(msan-module),function(msan)' 2>&1 | FileCheck -allow-deprecated-dag-overlap -check-prefixes=CHECK,INSTR %s
+; RUN: opt < %s -msan-check-access-address=0 -S -passes='module(msan-module),function(msan)' -msan-no-sanitize-all=1 2>&1 | FileCheck -allow-deprecated-dag-overlap -check-prefixes=CHECK,NOSANITIZE %s
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+declare void @bar()
+
+define i32 @SanitizeFn(i32 %x) uwtable sanitize_memory {
+entry:
+  %tobool = icmp eq i32 %x, 0
+  br i1 %tobool, label %if.end, label %if.then
+
+if.then:                                          ; preds = %entry
+  tail call void @bar()
+  br label %if.end
+
+if.end:                                           ; preds = %entry, %if.then
+  ret i32 %x
+}
+
+; CHECK-LABEL: @SanitizeFn
+; INSTR: @__msan_warning
+; NOSANITIZE-NOT: @__msan_warning
+; NOSANITIZE: store i32 0, {{.*}} @__msan_retval_tls
+; CHECK: ret i32
+
+
+define i32 @NoSanitizeFn(i32 %x) uwtable {
+entry:
+  %tobool = icmp eq i32 %x, 0
+  br i1 %tobool, label %if.end, label %if.then
+
+if.then:                                          ; preds = %entry
+  tail call void @bar()
+  br label %if.end
+
+if.end:                                           ; preds = %entry, %if.then
+  ret i32 %x
+}
+
+
+; CHECK-LABEL: @NoSanitizeFn
+; CHECK-NOT: @__msan_warning
+; CHECK: store i32 0, {{.*}} @__msan_retval_tls
+; CHECK: ret i32
+