sparse-llvm subtraction of one pointer from another should result in int difference

sparse-llvm subtraction of one pointer from another should result in int difference

[Dibyendu Majumdar]

Hi,

I was investigating an error reported while compiling minilua (please
see my earlier post on minlua) and I found that one of the issues was
that the result of subtracting one pointer from another is not handled
correctly in sparse-llvm. I think the OP_SUB implementation should be
changed as follows:

 case OP_SUB:
  if (symbol_is_fp_type(C, insn->type))
   target = LLVMBuildFSub(fn->builder, lhs, rhs, target_name);
  else if (LLVMGetTypeKind(LLVMTypeOf(lhs)) == LLVMPointerTypeKind &&
   LLVMGetTypeKind(LLVMTypeOf(rhs)) == LLVMPointerTypeKind) {
   // Both arguments are pointer
   // Result will be integer
   lhs = LLVMBuildPtrToInt(fn->builder, lhs,
LLVMIntType(C->target->bits_in_pointer), "");
   rhs = LLVMBuildPtrToInt(fn->builder, rhs,
LLVMIntType(C->target->bits_in_pointer), "");
   target = LLVMBuildSub(fn->builder, lhs, rhs, target_name);
  }
  else
   target = LLVMBuildSub(fn->builder, lhs, rhs, target_name);
  break;

Thanks and Regards
Dibyendu

Re: sparse-llvm subtraction of one pointer from another should result in int difference

[Luc Van Oostenryck]

On Mon, Mar 13, 2017 at 08:59:02PM +0000, Dibyendu Majumdar wrote:
> Hi,
> 
> I was investigating an error reported while compiling minilua (please
> see my earlier post on minlua) and I found that one of the issues was
> that the result of subtracting one pointer from another is not handled
> correctly in sparse-llvm.

This is fixed in the llvm-fixes-v3 serie I submitted yesterday.

-- Luc