[sanitizer] Simplify and future-proof maybeMarkSanitizerLibraryCallNoBuiltin().

Sanitizers set nobuiltin attribute on certain library functions to
avoid a situation where such function is neither instrumented nor
intercepted.

At the moment the list of interesting functions is hardcoded. This
change replaces it with logic based on
TargetLibraryInfo::hasOptimizedCodegen and the presense of readnone
function attribute (sanitizers are generally interested in memory
behavior of library functions).

This is expected to be a no-op change: the new logic matches exactly
the same set of functions.

r276771 (currently reverted) added mempcpy() to the list, breaking
MSan tests. With this change, r276771 can be safely re-landed.

llvm-svn: 277086

1 files changed, 6 insertions, 17 deletions

diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 40432680e38..3148bae292e 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -1954,23 +1954,12 @@ bool llvm::recognizeBSwapOrBitReverseIdiom(
 // in ASan/MSan/TSan/DFSan, and thus make us miss some memory accesses,
 // we mark affected calls as NoBuiltin, which will disable optimization
 // in CodeGen.
-void llvm::maybeMarkSanitizerLibraryCallNoBuiltin(CallInst *CI,
-                                          const TargetLibraryInfo *TLI) {
+void llvm::maybeMarkSanitizerLibraryCallNoBuiltin(
+    CallInst *CI, const TargetLibraryInfo *TLI) {
   Function *F = CI->getCalledFunction();
   LibFunc::Func Func;
-  if (!F || F->hasLocalLinkage() || !F->hasName() ||
-      !TLI->getLibFunc(F->getName(), Func))
-    return;
-  switch (Func) {
-    default: break;
-    case LibFunc::memcmp:
-    case LibFunc::memchr:
-    case LibFunc::strcpy:
-    case LibFunc::stpcpy:
-    case LibFunc::strcmp:
-    case LibFunc::strlen:
-    case LibFunc::strnlen:
-      CI->addAttribute(AttributeSet::FunctionIndex, Attribute::NoBuiltin);
-      break;
-  }
+  if (F && !F->hasLocalLinkage() && F->hasName() &&
+      TLI->getLibFunc(F->getName(), Func) && TLI->hasOptimizedCodeGen(Func) &&
+      !F->doesNotAccessMemory())
+    CI->addAttribute(AttributeSet::FunctionIndex, Attribute::NoBuiltin);
 }