[Bug target/19704] New: regparm vs dllimport of C++ methods

[dannysmith at users dot sourceforge dot net]

C++ methods that have both dllimport and regparm(3) can result in 
"unable to find a register to spill in class 'CREG'" error message when 
compiled at -O2 or -Os

This causes windows port of Mozilla to fail as reported at:
https://sourceforge.net/tracker/?
func=detail&atid=102435&aid=1112123&group_id=2435

Here is reduced testcase:
// imp_regparm_method.cpp

struct Bar
{ 
  char* data;
  int getlen() const;
  char* getdata() const;
  __declspec(dllimport) void __attribute__ ((regparm(3))) assign(char*, int);
};

struct Foo
{
        Bar foobar;
        void GetData();
};

void Foo::GetData()
{
    foobar.assign(foobar.getdata(), foobar.getlen());
}


g++ -c -Os imp_regparm_method.cpp 

C:\WINNT\Profiles\danny\Desktop>g++-4.0.0  -c -Os imp_regparm_method.cpp 
imp_regparm_method.cpp: In member function 'void Foo::GetData()':
imp_regparm_method.cpp:18: error: unable to find a register to spill in 
class 'CREG'
imp_regparm_method.cpp:18: error: this is the insn:
(call_insn/j:HI 24 23 25 0 (call (mem:QI (reg/f:SI 4 si [62]) [0 S1 A8])
        (const_int 0 [0x0])) 358 {*sibcall_1} (insn_list:REG_DEP_TRUE 20 
(insn_list:REG_DEP_TRUE 21 (insn_list:REG_DEP_TRUE 22 (insn_list:REG_DEP_TRUE 
23 (nil)))))
    (expr_list:REG_DEAD (reg:SI 2 cx [ D.1581 ])
        (expr_list:REG_DEAD (reg:SI 1 dx [ D.1582 ])
            (expr_list:REG_DEAD (reg:SI 0 ax [ D.1580 ])
                (expr_list:REG_DEAD (reg/f:SI 4 si [62])
                    (nil)))))
    (expr_list:REG_DEP_TRUE (use (reg:SI 0 ax [ D.1580 ]))
        (expr_list:REG_DEP_TRUE (use (reg:SI 1 dx [ D.1582 ]))
            (expr_list:REG_DEP_TRUE (use (reg:SI 2 cx [ D.1581 ]))
                (nil)))))
imp_regparm_method.cpp:18: confused by earlier errors, bailing out



Changing regparm(3) to regparm(2) avoids the error.
Removing dllimport attribute  avoids the error.
Making Foo::GetData inline avoids the error.

The failure occurs with GCC 4.0 and 3.4.4.  But not with 3.3.3 nor 2.95.3

Danny

-- 
           Summary: regparm vs dllimport of C++ methods
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dannysmith at users dot sourceforge dot net
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-mingw32
  GCC host triplet: i686-pc-mingw32
GCC target triplet: i686-pc-mingw32


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19704