[LLVMbugs] [Bug 6995] New: C++ classes get lowered to gross IR types

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=6995

           Summary: C++ classes get lowered to gross IR types
           Product: clang
           Version: unspecified
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: LLVM Codegen
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: clattner at apple.com
                CC: llvmbugs at cs.uiuc.edu


In some thing like the example below, we compile the struct types to this:

%0 = type { i8*, i8* }
%1 = type { i8*, i8*, i32, i32, i8*, i64, i8*, i64 }
%2 = type { i8*, i8*, i8* }
%struct.A = type { i8** }
%struct.B = type { i8** }
%struct.C = type { [16 x i8] }
%struct.D = type { [16 x i8] }

This is really nasty, llvm-gcc produces something much more friendly to the
optimizers:

%struct.A = type { i32 (...)** }
%struct.B = type { i32 (...)** }
%struct.C = type { %struct.A, %struct.A }
%struct.D = type { %struct.C }


struct A {
  virtual int f() { return 1; }
};

struct B {
  virtual int f() { return 2; }
};

struct C : A, B {
  virtual int f() { return 3; }
};

struct D : C {
  virtual int f() { return 4; }
};

static int f(D* d) {
  B* b = d;
  return b->f();
};

int g() {
  D d;

  return f(&d);
}

-- 
Configure bugmail: http://llvm.org/bugs/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.