[llvm-commits] [llvm] r72213 - in /llvm/trunk: bindings/ocaml/llvm/llvm.mli include/llvm/Constants.h lib/VMCore/Constants.cpp lib/VMCore/Core.cpp

[Duncan Sands]

Author: baldrick
Date: Thu May 21 10:52:21 2009
New Revision: 72213

URL: http://llvm.org/viewvc/llvm-project?rev=72213&view=rev
Log:
Add a getAlignOf helper for getting the ABI alignment of a
type as a target independent constant expression.  I confess
that I didn't check that this method works as intended (though
I did test the equivalent hand-written IR a little).  But what
could possibly go wrong!

Modified:
    llvm/trunk/bindings/ocaml/llvm/llvm.mli
    llvm/trunk/include/llvm/Constants.h
    llvm/trunk/lib/VMCore/Constants.cpp
    llvm/trunk/lib/VMCore/Core.cpp

Modified: llvm/trunk/bindings/ocaml/llvm/llvm.mli
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/bindings/ocaml/llvm/llvm.mli?rev=72213&r1=72212&r2=72213&view=diff

==============================================================================
--- llvm/trunk/bindings/ocaml/llvm/llvm.mli (original)
+++ llvm/trunk/bindings/ocaml/llvm/llvm.mli Thu May 21 10:52:21 2009
@@ -514,9 +514,15 @@
 
 (** {7 Constant expressions} *)
 
+(** [align_of ty] returns the alignof constant for the type [ty]. This is
+    equivalent to [const_ptrtoint (const_gep (const_null (pointer_type {i8,ty}))
+    (const_int i32_type 0) (const_int i32_type 1)) i32_type], but considerably
+    more readable.  See the method [llvm::ConstantExpr::getAlignOf]. *)
+external align_of : lltype -> llvalue = "LLVMAlignOf"
+
 (** [size_of ty] returns the sizeof constant for the type [ty]. This is
     equivalent to [const_ptrtoint (const_gep (const_null (pointer_type ty))
-    (const_int i64_type 1)) i64_type], but considerably more readable.
+    (const_int i32_type 1)) i64_type], but considerably more readable.
     See the method [llvm::ConstantExpr::getSizeOf]. *)
 external size_of : lltype -> llvalue = "LLVMSizeOf"
 

Modified: llvm/trunk/include/llvm/Constants.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Constants.h?rev=72213&r1=72212&r2=72213&view=diff

==============================================================================
--- llvm/trunk/include/llvm/Constants.h (original)
+++ llvm/trunk/include/llvm/Constants.h Thu May 21 10:52:21 2009
@@ -680,6 +680,12 @@
     return getSelectTy(V1->getType(), C, V1, V2);
   }
 
+  /// getAlignOf constant expr - computes the alignment of a type in a target
+  /// independent way (Note: the return type is an i32; Note: assumes that i8
+  /// is byte aligned).
+  ///
+  static Constant *getAlignOf(const Type *Ty);
+
   /// getSizeOf constant expr - computes the size of a type in a target
   /// independent way (Note: the return type is an i64).
   ///

Modified: llvm/trunk/lib/VMCore/Constants.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/VMCore/Constants.cpp?rev=72213&r1=72212&r2=72213&view=diff

==============================================================================
--- llvm/trunk/lib/VMCore/Constants.cpp (original)
+++ llvm/trunk/lib/VMCore/Constants.cpp Thu May 21 10:52:21 2009
@@ -2082,6 +2082,17 @@
   return getFoldedCast(Instruction::BitCast, C, DstTy);
 }
 
+Constant *ConstantExpr::getAlignOf(const Type *Ty) {
+  // alignof is implemented as: (i64) gep ({i8,Ty}*)null, 0, 1
+  const Type *AligningTy = StructType::get(Type::Int8Ty, Ty, NULL);
+  Constant *NullPtr = getNullValue(AligningTy->getPointerTo());
+  Constant *Zero = ConstantInt::get(Type::Int32Ty, 0);
+  Constant *One = ConstantInt::get(Type::Int32Ty, 1);
+  Constant *Indices[2] = { Zero, One };
+  Constant *GEP = getGetElementPtr(NullPtr, Indices, 2);
+  return getCast(Instruction::PtrToInt, GEP, Type::Int32Ty);
+}
+
 Constant *ConstantExpr::getSizeOf(const Type *Ty) {
   // sizeof is implemented as: (i64) gep (Ty*)null, 1
   Constant *GEPIdx = ConstantInt::get(Type::Int32Ty, 1);

Modified: llvm/trunk/lib/VMCore/Core.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/VMCore/Core.cpp?rev=72213&r1=72212&r2=72213&view=diff

==============================================================================
--- llvm/trunk/lib/VMCore/Core.cpp (original)
+++ llvm/trunk/lib/VMCore/Core.cpp Thu May 21 10:52:21 2009
@@ -356,6 +356,10 @@
 
 /*--.. Constant expressions ................................................--*/
 
+LLVMValueRef LLVMAlignOf(LLVMTypeRef Ty) {
+  return wrap(ConstantExpr::getAlignOf(unwrap(Ty)));
+}
+
 LLVMValueRef LLVMSizeOf(LLVMTypeRef Ty) {
   return wrap(ConstantExpr::getSizeOf(unwrap(Ty)));
 }