LLVM Changes for alloc_align

GCC has the alloc_align attribute, which is similar to assume_aligned, except the attribute's parameter is the index of the integer parameter that needs aligning to.

This is the required LLVM changes to make this happen.

Differential Revision: https://reviews.llvm.org/D29598

llvm-svn: 298643

llvm/include/llvm/IR/IRBuilder.h

@@ -1806,24 +1806,16 @@ class IRBuilder : public IRBuilderBase, public Inserter {
     return V;
   }
 
-  /// \brief Create an assume intrinsic call that represents an alignment
-  /// assumption on the provided pointer.
-  ///
-  /// An optional offset can be provided, and if it is provided, the offset
-  /// must be subtracted from the provided pointer to get the pointer with the
-  /// specified alignment.
-  CallInst *CreateAlignmentAssumption(const DataLayout &DL, Value *PtrValue,
-                                      unsigned Alignment,
-                                      Value *OffsetValue = nullptr) {
-    assert(isa<PointerType>(PtrValue->getType()) &&
-           "trying to create an alignment assumption on a non-pointer?");
-
-    PointerType *PtrTy = cast<PointerType>(PtrValue->getType());
-    Type *IntPtrTy = getIntPtrTy(DL, PtrTy->getAddressSpace());
+private:
+  /// \brief Helper function that creates an assume intrinsic call that
+  /// represents an alignment assumption on the provided Ptr, Mask, Type
+  /// and Offset.
+  CallInst *CreateAlignmentAssumptionHelper(const DataLayout &DL,
+                                            Value *PtrValue, Value *Mask,
+                                            Type *IntPtrTy,
+                                            Value *OffsetValue) {
     Value *PtrIntValue = CreatePtrToInt(PtrValue, IntPtrTy, "ptrint");
 
-    Value *Mask = ConstantInt::get(IntPtrTy,
-      Alignment > 0 ? Alignment - 1 : 0);
     if (OffsetValue) {
       bool IsOffsetZero = false;
       if (ConstantInt *CI = dyn_cast<ConstantInt>(OffsetValue))
@@ -1840,9 +1832,60 @@ class IRBuilder : public IRBuilderBase, public Inserter {
     Value *Zero = ConstantInt::get(IntPtrTy, 0);
     Value *MaskedPtr = CreateAnd(PtrIntValue, Mask, "maskedptr");
     Value *InvCond = CreateICmpEQ(MaskedPtr, Zero, "maskcond");
-
     return CreateAssumption(InvCond);
   }
+
+public:
+  /// \brief Create an assume intrinsic call that represents an alignment
+  /// assumption on the provided pointer.
+  ///
+  /// An optional offset can be provided, and if it is provided, the offset
+  /// must be subtracted from the provided pointer to get the pointer with the
+  /// specified alignment.
+  CallInst *CreateAlignmentAssumption(const DataLayout &DL, Value *PtrValue,
+                                      unsigned Alignment,
+                                      Value *OffsetValue = nullptr) {
+    assert(isa<PointerType>(PtrValue->getType()) &&
+           "trying to create an alignment assumption on a non-pointer?");
+    PointerType *PtrTy = cast<PointerType>(PtrValue->getType());
+    Type *IntPtrTy = getIntPtrTy(DL, PtrTy->getAddressSpace());
+
+    Value *Mask = ConstantInt::get(IntPtrTy, Alignment > 0 ? Alignment - 1 : 0);
+    return CreateAlignmentAssumptionHelper(DL, PtrValue, Mask, IntPtrTy,
+                                           OffsetValue);
+  }
+  //
+  /// \brief Create an assume intrinsic call that represents an alignment
+  /// assumption on the provided pointer.
+  ///
+  /// An optional offset can be provided, and if it is provided, the offset
+  /// must be subtracted from the provided pointer to get the pointer with the
+  /// specified alignment.
+  ///
+  /// This overload handles the condition where the Alignment is dependent
+  /// on an existing value rather than a static value.
+  CallInst *CreateAlignmentAssumption(const DataLayout &DL, Value *PtrValue,
+                                      Value *Alignment,
+                                      Value *OffsetValue = nullptr) {
+    assert(isa<PointerType>(PtrValue->getType()) &&
+           "trying to create an alignment assumption on a non-pointer?");
+    PointerType *PtrTy = cast<PointerType>(PtrValue->getType());
+    Type *IntPtrTy = getIntPtrTy(DL, PtrTy->getAddressSpace());
+
+    if (Alignment->getType() != IntPtrTy)
+      Alignment = CreateIntCast(Alignment, IntPtrTy, /*isSigned*/ true,
+                                "alignmentcast");
+    Value *IsPositive =
+        CreateICmp(CmpInst::ICMP_SGT, Alignment,
+                   ConstantInt::get(Alignment->getType(), 0), "ispositive");
+    Value *PositiveMask =
+        CreateSub(Alignment, ConstantInt::get(IntPtrTy, 1), "positivemask");
+    Value *Mask = CreateSelect(IsPositive, PositiveMask,
+                               ConstantInt::get(IntPtrTy, 0), "mask");
+
+    return CreateAlignmentAssumptionHelper(DL, PtrValue, Mask, IntPtrTy,
+                                           OffsetValue);
+  }
 };
 
 // Create wrappers for C Binding types (see CBindingWrapping.h).