[Bug target/64160] New: msp430 code generation error adding 32-bit integers

[pab at pabigot dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64160

            Bug ID: 64160
           Summary: msp430 code generation error adding 32-bit integers
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pab at pabigot dot com

This program:

struct adjustment {
  unsigned long duration;
};
unsigned long read_clock ();
int dosomething (struct adjustment * ap, unsigned long v);
int doit (struct adjustment * ap)
{
  return dosomething(ap, read_clock() + ap->duration);
}

when compiled with msp430-elf-gcc -Os -S produces:

       ; start of prologue
        PUSHM.W #1, R10
        ; end of prologue
        MOV.W   R12, R10
        CALL    #read_clock
        MOV.W   @R10, R13    <<-- error half of return value clobbered
        ADD     R12, R13 ; cy
        MOV.W   2(R10), R14
        ADDC    R13, R14     <<-- R13 is not what it should be
        MOV.W   R10, R12
        CALL    #dosomething

which produces the wrong answer because the upper word of the result from
read_clock was overwritten by the read from memory.