Add argmemonly attribute.

This change adds new attribute called "argmemonly". Function marked with this attribute can only access memory through it's argument pointers. This attribute directly corresponds to the "OnlyAccessesArgumentPointees" ModRef behaviour in alias analysis.

Differential Revision: http://reviews.llvm.org/D10398

llvm-svn: 241979

2 files changed, 12 insertions, 4 deletions

diff --git a/llvm/lib/IR/Attributes.cpp b/llvm/lib/IR/Attributes.cpp
index c3032f4ffc7..546a98670a2 100644
--- a/llvm/lib/IR/Attributes.cpp
+++ b/llvm/lib/IR/Attributes.cpp
@@ -190,6 +190,8 @@ std::string Attribute::getAsString(bool InAttrGrp) const {
     return "sanitize_address";
   if (hasAttribute(Attribute::AlwaysInline))
     return "alwaysinline";
+  if (hasAttribute(Attribute::ArgMemOnly))
+    return "argmemonly";
   if (hasAttribute(Attribute::Builtin))
     return "builtin";
   if (hasAttribute(Attribute::ByVal))
@@ -447,6 +449,9 @@ uint64_t AttributeImpl::getAttrMask(Attribute::AttrKind Val) {
     llvm_unreachable("dereferenceable_or_null attribute not supported in raw "
                      "format");
     break;
+  case Attribute::ArgMemOnly:
+    llvm_unreachable("argmemonly attribute not supported in raw format");
+    break;
   }
   llvm_unreachable("Unsupported attribute type");
 }
@@ -1356,7 +1361,8 @@ AttrBuilder &AttrBuilder::addRawValue(uint64_t Val) {
   for (Attribute::AttrKind I = Attribute::None; I != Attribute::EndAttrKinds;
        I = Attribute::AttrKind(I + 1)) {
     if (I == Attribute::Dereferenceable ||
-        I == Attribute::DereferenceableOrNull)
+        I == Attribute::DereferenceableOrNull ||
+        I == Attribute::ArgMemOnly)
       continue;
     if (uint64_t A = (Val & AttributeImpl::getAttrMask(I))) {
       Attrs[I] = true;
diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index 647920f23da..2a0a4ff393e 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -1273,7 +1273,8 @@ void Verifier::VerifyAttributeTypes(AttributeSet Attrs, unsigned Idx,
         I->getKindAsEnum() == Attribute::Cold ||
         I->getKindAsEnum() == Attribute::OptimizeNone ||
         I->getKindAsEnum() == Attribute::JumpTable ||
-        I->getKindAsEnum() == Attribute::Convergent) {
+        I->getKindAsEnum() == Attribute::Convergent ||
+        I->getKindAsEnum() == Attribute::ArgMemOnly) {
       if (!isFunction) {
         CheckFailed("Attribute '" + I->getAsString() +
                     "' only applies to functions!", V);
@@ -1531,8 +1532,9 @@ void Verifier::VerifyStatepoint(ImmutableCallSite CS) {
 
   const Instruction &CI = *CS.getInstruction();
 
-  Assert(!CS.doesNotAccessMemory() && !CS.onlyReadsMemory(),
-         "gc.statepoint must read and write memory to preserve "
+  Assert(!CS.doesNotAccessMemory() && !CS.onlyReadsMemory() &&
+         !CS.onlyAccessesArgMemory(),
+         "gc.statepoint must read and write all memory to preserve "
          "reordering restrictions required by safepoint semantics",
          &CI);