Hello,
First of all I am not sure if this is the correct forum to report this problem, or even if it has been detected already. Nevertheless I am posting it here in the hope that somebody might read it and take this problem into account.
In a project previously developed with CodeEarrior V6.4 wich for the following C code generated the following assembler:
// -----------------------------
unsigned short status ;
unsigned short my_function (void) ;
status = my_function () ;
if ((status == 0x2102) || (status == 0x210B) || (status == 0x210A)) {
bla bla ;
}
else {
bla bla ;
}
// --------------
CodeWarrior V6.4 with "Faster Execution Speed" And "Level 4" Optimization:
0x00000076 0x7400 moveq#0,d2
0x00000078 0x3400 move.wd0,d2
0x0000007A 0x0C8200002102 cmpi.l#8450,d2 ; '..!.'
0x00000080 0x670000B4 beq.w*+182 ; 0x00000136
0x00000084 0x06800000DEF6 addi.l#57078,d0 ; '....'
0x0000008A 0x7200 moveq#0,d1
0x0000008C 0x3200 move.wd0,d1
0x0000008E 0x0C8100000001 cmpi.l#1,d1 ; '....'
0x00000094 0x630000A0 bls.w*+162 ; 0x00000136
Status is in d0, and a special trick is made to test the two last consecutive values. By adding #57078 to the returned value in a 2 byte operation we will get a value of #0 or #1 depending on the value on d0 being 0x210B, or 0x210A. The we can check if the result value is less or equal to #1.
Under CodeWarrior V7.1 with "Faster Execution Speed" And "Level 4" Optimization:
0x00000076 0x7200 moveq #0,d1
0x00000078 0x3200 move.w d0,d1
0x0000007A 0x0C8100002102 cmpi.l #8450,d1 ; '..!.'
0x00000080 0x670000AC beq.w *+174 ; 0x0000012e
0x00000084 0x7200 moveq #0,d1
0x00000086 0x3200 move.w d0,d1
0x00000088 0x06810000DEF6 addi.l #57078,d1 ; '....'
0x0000008E 0x0C8100000001 cmpi.l #1,d1 ; '....'
0x00000094 0x63000098 bls.w *+154 ; 0x0000012e
Here status is also in d0, and the same trick is attempted, but there is a catch.
With V6.4 the value of #57078 is added to d0 an then d0 is moved to d1 (just the two lower bytes) correctly truncating the value to two bytes.
But in V7.1 we get the value of #57078 added instead to d1 in a 4 byte long addition and then comparing it with #1 also in a 4 byte long operation. For the trick to work the result of the addition must pe truncated to 2 bytes. This code does not work!
Thank you
Gabriel
