Hi Luc,
On 28 March 2017 at 14:34, Luc Van Oostenryck
<luc.vanoostenryck@xxxxxxxxx> wrote:
> On Tue, Mar 28, 2017 at 2:40 PM, Dibyendu Majumdar
> <mobile@xxxxxxxxxxxxxxx> wrote:
>> I am getting a failure in following test when simplifications are enabled:
>>
>> extern int printf(const char *, ...);
>>
>> int main(void)
>> {
>> struct{
>> int twobit:2;
>> int :1;
>> int threebit:3;
>> unsigned int onebit:1;
>> } s3;
>>
>> s3.onebit = 1;
>> if(s3.onebit != 1){
>> printf("Be especially careful with 1-bit fields! %d\n", (int) s3.onebit);
>> return 1;
>> }
>> return 0;
>> }
>>
>> The output (truncated) from linearizer without simplications is this:
>>
>> main:
>> .L0:
>> <entry-point>
>> load.32 %r1 <- 0[s3]
>> shl.32 %r2 <- $1, $6
>> and.32 %r3 <- %r1, $-65
>> or.32 %r4 <- %r3, %r2
>> store.32 %r4 -> 0[s3]
>> load.32 %r5 <- 0[s3]
>> lsr.32 %r6 <- %r5, $6
>> cast.32 %r7 <- (1) %r6
>> setne.32 %r8 <- %r7, $1
>> br %r8, .L1, .L2
>>
>> But if simplifications are on then we get:
>>
>> main:
>> .L0:
>> <entry-point>
>> and.32 %r3 <- %r4, $-65
>> or.32 %r4 <- %r3, $64
>> lsr.32 %r6 <- %r4, $6
>> cast.32 %r7 <- (1) %r6
>> setne.32 %r8 <- %r7, $1
>> br %r8, .L1, .L3
>
> Are you worried about the load of s3 (wich is not initialized)?
> Or the store of s3 (wich is local and never used but for .onebit)?
> Or the size of %r6 (which is created as 32bit but used as 1bit)?
>
> If the later, you're missing the patch
> https://git.kernel.org/pub/scm/devel/sparse/sparse.git/commit/?h=sparse-next&id=522773d089700cce5551860aea3cb93f40b5f3a4
>
The first instruction and.32 refers to %r4 which is undefined.
Regards
Dibyendu
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