Add a dereferenceable attribute
This attribute indicates that the parameter or return pointer is
dereferenceable. Practically speaking, loads from such a pointer within the
associated byte range are safe to speculatively execute. Such pointer
parameters are common in source languages (C++ references, for example).
llvm-svn: 213385
diff --git a/llvm/lib/IR/Function.cpp b/llvm/lib/IR/Function.cpp
index 1443571..de59b26 100644
--- a/llvm/lib/IR/Function.cpp
+++ b/llvm/lib/IR/Function.cpp
@@ -77,11 +77,17 @@
}
/// hasNonNullAttr - Return true if this argument has the nonnull attribute on
-/// it in its containing function.
+/// it in its containing function. Also returns true if at least one byte is
+/// known to be dereferenceable and the pointer is in addrspace(0).
bool Argument::hasNonNullAttr() const {
if (!getType()->isPointerTy()) return false;
- return getParent()->getAttributes().
- hasAttribute(getArgNo()+1, Attribute::NonNull);
+ if (getParent()->getAttributes().
+ hasAttribute(getArgNo()+1, Attribute::NonNull))
+ return true;
+ else if (getDereferenceableBytes() > 0 &&
+ getType()->getPointerAddressSpace() == 0)
+ return true;
+ return false;
}
/// hasByValAttr - Return true if this argument has the byval attribute on it
@@ -113,6 +119,12 @@
}
+uint64_t Argument::getDereferenceableBytes() const {
+ assert(getType()->isPointerTy() &&
+ "Only pointers have dereferenceable bytes");
+ return getParent()->getDereferenceableBytes(getArgNo()+1);
+}
+
/// hasNestAttr - Return true if this argument has the nest attribute on
/// it in its containing function.
bool Argument::hasNestAttr() const {