Cosmic compiler producing wrong asm

[mchahn]

I couldn't find a forum for the cosmic compiler. If anyone knows of one let me know and I'll ask there instead.

I have code that is compiling wrong. A function has a u16 parameter and that param is being referenced as u8. This is the declaration of the function ...

u16 getTempFromAdcCount(u16 count);

This is the function ...

u16 getTempFromAdcCount(u16 count) {
 u8 countOfs, lowIdx, idxOfs;
 u16 lowTemp, hiTemp, tempDiff;
 if(count < MIN_ADC_COUNT) return 200*10;
 if(count >= MAX_ADC_COUNT) return 0;
 count -= MIN_ADC_COUNT;
 lowIdx = countOfs >> DELTA_SHIFT;
 idxOfs = countOfs & DELTA_MASK;
 hiTemp = tempTable[lowIdx];
 if(idxOfs == 0) 
 return hiTemp;
 lowTemp = tempTable[lowIdx+1];
 tempDiff = hiTemp - lowTemp;
 return hiTemp - ((tempDiff * idxOfs) >> DELTA_SHIFT);
}

This is the call ...

 temp = getTempFromAdcCount(adjCount);

This is the asm for the call. Note that the param is correctly pushing u16 on the stack ...

 106 ; 23 temp = getTempFromAdcCount(adjCount);
 108 0023 1e01 	ldw	x,(OFST-1,sp)
 109 0025 cd0000 	call	_getTempFromAdcCount
 111 0028 1f01 	ldw	(OFST-1,sp),x

And this is the incorrect asm for the function being called. Note that it is treating the param as u8 ...

 225 0000 _getTempFromAdcCount:
 227 0000 89 	pushw	x
 228 0001 5208 	subw	sp,#8
 229 00000008 OFST:	set	8
 232 ; 147 if(count < MIN_ADC_COUNT) return 200*10;
 234 0003 a30020 	cpw	x,#32
 235 0006 2405 	jruge	L75
 238 0008 ae07d0 	ldw	x,#2000
 240 000b 2008 	jra	L6
 241 000d L75:
 242 ; 148 if(count >= MAX_ADC_COUNT) return 0;
 244 000d 1e09 	ldw	x,(OFST+1,sp)
 245 000f a30388 	cpw	x,#904
 246 0012 2504 	jrult	L16
 249 0014 5f 	clrw	x
 251 0015 L6:
 253 0015 5b0a 	addw	sp,#10
 254 0017 81 	ret
 255 0018 L16:
 256 ; 149 countOfs = count - MIN_ADC_COUNT;
 258 0018 7b0a 	ld	a,(OFST+2,sp)
 259 001a a020 	sub	a,#32
 260 001c 6b08 	ld	(OFST+0,sp),a
...snip...

Can anyone tell me what is going on?

[mchahn]

Correction. I showed asm for a different version of the code. Just note that this code in the function has the wrong asm ...

 256 ; 149 countOfs = count - MIN_ADC_COUNT;
 258 0018 7b0a 	ld	a,(OFST+2,sp) <-- should be u16
 259 001a a020 	sub	a,#32
 260 001c 6b08 	ld	(OFST+0,sp),a

[Tesla DeLorean]

countOfs is however a u8

Try

#define MIN_ADC_COUNT ((u16)32)

[mchahn]

And also, this is the definition of MIN_ADC_COUNT

#define MIN_ADC_COUNT 32 // index for adc count 32 is 0

[mchahn]

Yes, the left-side, countOfs, is a u8. But it should do the u16 arithmetic in 16-bit and then auto-convert the result to 8-bit to store in countOfs. I'll change countOfs to u16 but I still think the compiler is wrong. From a google search ...

• All the data types of the variables are upgraded to the data type of the variable with largest data type.

[Tesla DeLorean]

Yeah, and you're probably using the optimizer.

The earlier code, does a min/max scoping, then masks and shifts.

Why on earth have an intermediate value that's not going to hold a number in the 32 .. 904 range, you're asking for some failure across the input number space.

[mchahn]

Thanks. It's a long story. Works fine now.