[msan] A no-op implementation of VarArg handling.

This stuff is used on platforms where MSan does not have a proper VarArg
implementation (anything other than x86_64 at the moment).

llvm-svn: 182375

3 files changed, 39 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
index cc5743b9380..d4664a95636 100644
--- a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
@@ -74,6 +74,7 @@
 #include "llvm/ADT/DepthFirstIterator.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Triple.h"
 #include "llvm/ADT/ValueMap.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/Function.h"
@@ -1963,9 +1964,29 @@ struct VarArgAMD64Helper : public VarArgHelper {
   }
 };
 
-VarArgHelper* CreateVarArgHelper(Function &Func, MemorySanitizer &Msan,
+/// \brief A no-op implementation of VarArgHelper.
+struct VarArgNoOpHelper : public VarArgHelper {
+  VarArgNoOpHelper(Function &F, MemorySanitizer &MS,
+                   MemorySanitizerVisitor &MSV) {}
+
+  void visitCallSite(CallSite &CS, IRBuilder<> &IRB) {}
+
+  void visitVAStartInst(VAStartInst &I) {}
+
+  void visitVACopyInst(VACopyInst &I) {}
+
+  void finalizeInstrumentation() {}
+};
+
+VarArgHelper *CreateVarArgHelper(Function &Func, MemorySanitizer &Msan,
                                  MemorySanitizerVisitor &Visitor) {
-  return new VarArgAMD64Helper(Func, Msan, Visitor);
+  // VarArg handling is only implemented on AMD64. False positives are possible
+  // on other platforms.
+  llvm::Triple TargetTriple(Func.getParent()->getTargetTriple());
+  if (TargetTriple.getArch() == llvm::Triple::x86_64)
+    return new VarArgAMD64Helper(Func, Msan, Visitor);
+  else
+    return new VarArgNoOpHelper(Func, Msan, Visitor);
 }
 
 }  // namespace
diff --git a/llvm/test/Instrumentation/MemorySanitizer/X86/vararg.ll b/llvm/test/Instrumentation/MemorySanitizer/X86/vararg.ll
new file mode 100644
index 00000000000..518c3dbf41d
--- /dev/null
+++ b/llvm/test/Instrumentation/MemorySanitizer/X86/vararg.ll
@@ -0,0 +1,15 @@
+; RUN: opt < %s -msan -msan-check-access-address=0 -S
+; Test that code using va_start can be compiled on i386.
+
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32-S128"
+target triple = "i386-unknown-linux-gnu"
+
+define void @VaStart(i8* %s, ...) {
+entry:
+  %vl = alloca i8*, align 4
+  %vl1 = bitcast i8** %vl to i8*
+  call void @llvm.va_start(i8* %vl1)
+  ret void
+}
+
+declare void @llvm.va_start(i8*)
diff --git a/llvm/test/Instrumentation/MemorySanitizer/msan_basic.ll b/llvm/test/Instrumentation/MemorySanitizer/msan_basic.ll
index 0d9ac8e1fd1..320860ce77b 100644
--- a/llvm/test/Instrumentation/MemorySanitizer/msan_basic.ll
+++ b/llvm/test/Instrumentation/MemorySanitizer/msan_basic.ll
@@ -1,6 +1,7 @@
 ; RUN: opt < %s -msan -msan-check-access-address=0 -S | FileCheck %s
 ; RUN: opt < %s -msan -msan-check-access-address=0 -msan-track-origins=1 -S | FileCheck -check-prefix=CHECK-ORIGINS %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"
 
 ; Check the presence of __msan_init
 ; CHECK: @llvm.global_ctors {{.*}} @__msan_init