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

include/llvm/IR/Attributes.h

@@ -282,6 +282,11 @@ public:
   AttributeSet removeAttributes(LLVMContext &C, unsigned Index, 
                                 AttributeSet Attrs) const;
 
+  /// \brief Add the dereferenceable attribute to the attribute set at the given
+  /// index. Since attribute sets are immutable, this returns a new set.
+  AttributeSet addDereferenceableAttr(LLVMContext &C, unsigned Index,
+                                      uint64_t Bytes) const;
+
   //===--------------------------------------------------------------------===//
   // AttributeSet Accessors
   //===--------------------------------------------------------------------===//

include/llvm/IR/Function.h

@@ -239,6 +239,9 @@ public:
   /// @brief removes the attributes from the list of attributes.
   void removeAttributes(unsigned i, AttributeSet attr);
 
+  /// @brief adds the dereferenceable attribute to the list of attributes.
+  void addDereferenceableAttr(unsigned i, uint64_t Bytes);
+
   /// @brief Extract the alignment for a call or parameter (0=unknown).
   unsigned getParamAlignment(unsigned i) const {
     return AttributeSets.getParamAlignment(i);

include/llvm/IR/Instructions.h

@@ -1375,6 +1375,9 @@ public:
   /// removeAttribute - removes the attribute from the list of attributes.
   void removeAttribute(unsigned i, Attribute attr);
 
+  /// \brief adds the dereferenceable attribute to the list of attributes.
+  void addDereferenceableAttr(unsigned i, uint64_t Bytes);
+
   /// \brief Determine whether this call has the given attribute.
   bool hasFnAttr(Attribute::AttrKind A) const {
     assert(A != Attribute::NoBuiltin &&
@@ -3056,6 +3059,9 @@ public:
   /// removeAttribute - removes the attribute from the list of attributes.
   void removeAttribute(unsigned i, Attribute attr);
 
+  /// \brief removes the dereferenceable attribute to the list of attributes.
+  void addDereferenceableAttr(unsigned i, uint64_t Bytes);
+
   /// \brief Determine whether this call has the given attribute.
   bool hasFnAttr(Attribute::AttrKind A) const {
     assert(A != Attribute::NoBuiltin &&

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
 //===----------------------------------------------------------------------===//

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

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());
 }

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, ...)
   }
   }

test/Transforms/InstCombine/gc.relocate.ll

@@ -0,0 +1,20 @@
+; RUN: opt < %s -datalayout -instcombine -S | FileCheck %s
+
+; Uses InstCombine with DataLayout to propagate dereferenceable
+; attribute via gc.relocate: if the derived ptr is dereferenceable(N),
+; then the return attribute of gc.relocate is dereferenceable(N).
+
+declare zeroext i1 @return_i1()
+declare i32 @llvm.experimental.gc.statepoint.p0f_i1f(i1 ()*, i32, i32, ...)
+declare i32 addrspace(1)* @llvm.experimental.gc.relocate.p1i32(i32, i32, i32)
+
+define i32 addrspace(1)* @deref(i32 addrspace(1)* dereferenceable(8) %dparam) {
+; Checks that a dereferenceabler pointer
+; CHECK-LABEL: @deref
+; CHECK: call dereferenceable(8)
+entry:
+    %load = load i32 addrspace(1)* %dparam
+    %tok = tail call i32 (i1 ()*, i32, i32, ...)* @llvm.experimental.gc.statepoint.p0f_i1f(i1 ()* @return_i1, i32 0, i32 0, i32 0, i32 addrspace(1)* %dparam)
+    %relocate = call i32 addrspace(1)* @llvm.experimental.gc.relocate.p1i32(i32 %tok, i32 4, i32 4)
+    ret i32 addrspace(1)* %relocate
+}