[cfe-dev] disabling loop idiom recognizer in clang

[Damjan Marion]

On Apr 29, 2011, at 12:24 AM, Chris Lattner wrote:

> 
> On Apr 28, 2011, at 3:17 PM, Damjan Marion wrote:
> 
>> On Apr 29, 2011, at 12:15 AM, Chris Lattner wrote:
>> 
>>> 
>>> On Apr 28, 2011, at 3:09 PM, Damjan Marion wrote:
>>> 
>>>> 
>>>> Hi,
>>>> 
>>>> is there a way to disable loop idiom recognizer in clang?
>>>> 
>>>> I have a problem with compiling early stage code for ARM architecture which should not be linked to external libraries but clang replaces loop with memset call in the code.
>>> 
>>> Yep, build with -fno-builtin or -ffreestanding.
>> 
>> It doesn't work. According to gcc docs (which clang probably follows): 
>> "GCC requires the freestanding environment provide memcpy, memmove, memset and memcmp."
> 
> Did you try it?  I'm aware of the requirements for a freestanding implementation.

Yes, I tried both. Here is output:

# bin/clang  -mcpu=arm926ej-s -Wa,-mcpu=arm926ej-s -ccc-host-triple arm-unknown-freebsd -mfloat-abi=soft -O2 -DKZIP -I. -I/Volumes/data/src/freebsd/sys -ffreestanding -fno-builtin -c /Volumes/data/src/freebsd/sys/kern/inflate.c -o inflate-tramp.o -g

# arm-none-eabi-objdump -S inflate-tramp.o | grep -B 5 -A 2 memset
     b58:	85900400 	ldrhi	r0, [r0, #1024]	; 0x400
     b5c:	e58d104c 	str	r1, [sp, #76]	; 0x4c
     b60:	e3a01000 	mov	r1, #0
     b64:	858d0030 	strhi	r0, [sp, #48]	; 0x30
     b68:	e24b0064 	sub	r0, fp, #100	; 0x64
     b6c:	ebfffffe 	bl	0 <memset>
	for (i = 0; i < BMAX+1; i++) c [i] = 0;