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MESC TOOL NEWS:
MESCT-NC79WA-980901D
NC79WA V.3.00 Release 1
Precaution
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Please take note of the following problem in using C compiler NC79WA (with assembler and integrated tool manager) for the 7900 series of microcomputers.
Problem on Optimize Option -OS
When optimize option -OS is given, the following incorrect codes are generated.
- If the result of evaluating an "if" statement is false, the code (an rts instruction etc.) for a return statement (or the end of a function) of the branch destination is not output.
- If data under control of a calling function exists in the frame area, the data cannot correctly be referenced.
Conditions
[Case 1] This problem may occur if the following three conditions are satisfied:
- Optimize option -OS is given.
- A return statement (or the end of a function) is designated as the branch destination of when the result of evaluating an "if" statement is false.
- A subroutine function is designated as the branch destination of when the result of evaluating the "if" statement is true, which is immediately followed by a return statement (or the end of a function).
[Case 2] This problem may occur if the following three conditions are satisfied:
- Optimize option -OS is given.
- A subroutine function accesses the frame area of the calling function.
- The subroutine function is immediately followed by a return statement (or the end of a function).
Examples
- Case 1
[C source File]
-------------------------------------------------------------------
unsigned int i, j, k;
void sub2(void);
void sub1(void)
{
if (i) {
if (j){ /* branch 1 */
sub2();
return;
}
/* branch 2 */
} else {
k = 0x01;
}
/* return */
}
-------------------------------------------------------------------
[Generated Codes]
-------------------------------------------------------------------
_sub1:
._line 7
;## # C_SRC : if (i){
lda A,DT+:_i
beq L2
._line 8
;## # C_SRC : if (j){ /* branch 1 */
lda A,DT+:_j
beq L4
._line 9
;## # C_SRC : sub2();
jmpl _sub2
L4:
; <=== rtl instruction not outputted
._line 13
;## # C_SRC : } else {
L2:
._line 14
;## # C_SRC : k = 0x01;
movm.W DT+:_k,#0001H
._line 17
;## # C_SRC : }
rtl
-------------------------------------------------------------------
- Case 2
[C Source File]
-------------------------------------------------------------------
void jmpsub( unsigned int near *);
unsigned int out;
void main(void)
{
unsigned int near i = 1;
jmpsub( (unsigned int near *)&i);
return;
}
void jmpsub( unsigned int near *p)
{
unsigned int arr[10];
arr[1] = 0;
out = *p;
}
-------------------------------------------------------------------
[Generated Codes]
-------------------------------------------------------------------
_main:
phd 0
subs #0002H
tsd
._line 6
;## # C_SRC : unsigned int near i = 1;
movm.W DP0:1,#0001H ; i
._line 7
;## # C_SRC : jmpsub( (unsigned int near *)&i);
tda 0
inc A
adds #0002H
pld 0 <=== Frame opened
jmpl $jmpsub
;
:
(middle lines omitted)
:
._line 12
;## # C_SRC : {
.DT __DT
.DP0 OFF
.glb $jmpsub
$jmpsub:
._line 16
;## # C_SRC : out = *p;
tax
lda A,DT+:0000H,X <=== Refers to the frame opened
sta A,DT+:_out
._line 17
;## # C_SRC : }
rtl
-------------------------------------------------------------------
Workaround
When you give optimize option -OS, give optimize blocking option "-Off = 2583" at the same time as described below:
- type command line
C:\> nc79 -OS -Off=2583 sample.c
- When TM used
Give an "-Off = 2583" option by using the [Options...] -> [Extra options] command after selecting [Environment] -> [Project Setting] -> [BUILD] -> [C Compiler].
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