InstCombine: propagate deref via new addDereferenceableAttr

The "dereferenceable" attribute cannot be added via .addAttribute(),
since it also expects a size in bytes. AttrBuilder#addAttribute or
AttributeSet#addAttribute is wrapped by classes Function, InvokeInst,
and CallInst. Add corresponding wrappers to
AttrBuilder#addDereferenceableAttr.

Having done this, propagate the dereferenceable attribute via
gc.relocate, adding a test to exercise it. Note that -datalayout is
required during execution over and above -instcombine, because
InstCombine only optionally requires DataLayoutPass.

Differential Revision: http://reviews.llvm.org/D7510

llvm-svn: 229265

4 files changed, 33 insertions, 2 deletions

diff --git a/llvm/lib/IR/Attributes.cpp b/llvm/lib/IR/Attributes.cpp
index 04545ea919a..daac6b5f639 100644
--- a/llvm/lib/IR/Attributes.cpp
+++ b/llvm/lib/IR/Attributes.cpp
@@ -835,6 +835,13 @@ AttributeSet AttributeSet::removeAttributes(LLVMContext &C, unsigned Index,
   return get(C, AttrSet);
 }
 
+AttributeSet AttributeSet::addDereferenceableAttr(LLVMContext &C, unsigned Index,
+                                                  uint64_t Bytes) const {
+  llvm::AttrBuilder B;
+  B.addDereferenceableAttr(Bytes);
+  return addAttributes(C, Index, AttributeSet::get(C, Index, B));
+}
+
 //===----------------------------------------------------------------------===//
 // AttributeSet Accessor Methods
 //===----------------------------------------------------------------------===//
diff --git a/llvm/lib/IR/Function.cpp b/llvm/lib/IR/Function.cpp
index fe44f17d686..33e15262524 100644
--- a/llvm/lib/IR/Function.cpp
+++ b/llvm/lib/IR/Function.cpp
@@ -343,6 +343,12 @@ void Function::removeAttributes(unsigned i, AttributeSet attrs) {
   setAttributes(PAL);
 }
 
+void Function::addDereferenceableAttr(unsigned i, uint64_t Bytes) {
+  AttributeSet PAL = getAttributes();
+  PAL = PAL.addDereferenceableAttr(getContext(), i, Bytes);
+  setAttributes(PAL);
+}
+
 // Maintain the GC name for each function in an on-the-side table. This saves
 // allocating an additional word in Function for programs which do not use GC
 // (i.e., most programs) at the cost of increased overhead for clients which do
diff --git a/llvm/lib/IR/Instructions.cpp b/llvm/lib/IR/Instructions.cpp
index 132800efeeb..8c4eeafdf84 100644
--- a/llvm/lib/IR/Instructions.cpp
+++ b/llvm/lib/IR/Instructions.cpp
@@ -346,6 +346,12 @@ void CallInst::removeAttribute(unsigned i, Attribute attr) {
   setAttributes(PAL);
 }
 
+void CallInst::addDereferenceableAttr(unsigned i, uint64_t Bytes) {
+  AttributeSet PAL = getAttributes();
+  PAL = PAL.addDereferenceableAttr(getContext(), i, Bytes);
+  setAttributes(PAL);
+}
+
 bool CallInst::hasFnAttrImpl(Attribute::AttrKind A) const {
   if (AttributeList.hasAttribute(AttributeSet::FunctionIndex, A))
     return true;
@@ -605,6 +611,12 @@ void InvokeInst::removeAttribute(unsigned i, Attribute attr) {
   setAttributes(PAL);
 }
 
+void InvokeInst::addDereferenceableAttr(unsigned i, uint64_t Bytes) {
+  AttributeSet PAL = getAttributes();
+  PAL = PAL.addDereferenceableAttr(getContext(), i, Bytes);
+  setAttributes(PAL);
+}
+
 LandingPadInst *InvokeInst::getLandingPadInst() const {
   return cast<LandingPadInst>(getUnwindDest()->getFirstNonPHI());
 }
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 87dc8621a95..53a90d05af7 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1127,11 +1127,17 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
     if (isKnownNonNull(DerivedPtr))
       II->addAttribute(AttributeSet::ReturnIndex, Attribute::NonNull);
 
-    // TODO: dereferenceable -> deref attribute
+    // isDereferenceablePointer -> deref attribute
+    if (DerivedPtr->isDereferenceablePointer(DL)) {
+      if (Argument *A = dyn_cast<Argument>(DerivedPtr)) {
+        uint64_t Bytes = A->getDereferenceableBytes();
+        II->addDereferenceableAttr(AttributeSet::ReturnIndex, Bytes);
+      }
+    }
 
     // TODO: bitcast(relocate(p)) -> relocate(bitcast(p))
     // Canonicalize on the type from the uses to the defs
-    
+
     // TODO: relocate((gep p, C, C2, ...)) -> gep(relocate(p), C, C2, ...)
   }
   }