[LLVMdev] bitwise AND selector node not commutative?

[Evan Cheng]

On Jun 25, 2009, at 6:06 PM, Evan Cheng wrote:

>
> On Jun 25, 2009, at 4:38 PM, David Goodwin wrote:
>
>> Using the Thumb-2 target we see that ORN ( a | ^b) and BIC (a & ^b)  
>> have similar patterns, as we would expect:
>>
>> defm t2BIC  : T2I_bin_irs<"bic", BinOpFrag<(and node:$LHS, (not  
>> node:$RHS))>>;
>> defm t2ORN  : T2I_bin_irs<"orn", BinOpFrag<(or  node:$LHS, (not  
>> node:$RHS))>>;
>>
>> Compiling the following three works as expected:
>>
>>    %tmp1 = xor i32 4294967295, %b ;   %tmp2 = or i32 %a, %tmp1   -- 
>> >  	orn r0, r0, r1
>>    %tmp1 = xor i32 4294967295, %b ;   %tmp2 = or i32 %tmp1, %a   -- 
>> >    orn r0, r0, r1
>>    %tmp = xor i32 %b, 4294967295  ;   %tmp1 = and i32 %a, %tmp   -- 
>> >    bic r0, r0, r1
>>
>> But this doesn't:
>>
>>    %tmp = xor i32 %b, 4294967295  ;   %tmp1 = and i32 %tmp, %a   -- 
>> >    eor r1, r1, #4294967295 ; and r0, r1, r0
>>
>> On the surface it seems that the selector is not commuting the AND  
>> operands. I've attached the complete test files. I can take a look  
>> but I need a pointer to get started.
>
> No, isel is trying to commute the AND. See ARMGenDAGISel.inc (auto- 
> generated by tablegen):
>
>     // Pattern: (and:i32 GPR:i32:$lhs, (xor:i32 t2_so_reg:i32:$rhs,  
> (imm:i32)<<P:Predicate_immAllOnes>>))
>     // Emits: (t2BICrs:i32 GPR:i32:$lhs, t2_so_reg:i32:$rhs)
>     // Pattern complexity = 19  cost = 1  size = 0
>     {
>       ..
>     }
>
>
>     // Pattern: (and:i32 (xor:i32 t2_so_reg:i32:$rhs, (imm:i32) 
> <<P:Predicate_immAllOnes>>), GPR:i32:$lhs)
>     // Emits: (t2BICrs:i32 GPR:i32:$lhs, t2_so_reg:i32:$rhs)
>     // Pattern complexity = 19  cost = 1  size = 0
>     {
>      ...
>      }
>
> The second one is the commuted version. Looks like the issue is in  
> SelectThumb2ShifterOperandReg.

Ugh. It should try to match t2BICrr. But someone tblgen is not  
generating the commuted version. Very strange. I'm take a look.

Evan

>
> Evan
>
>
>>
>> David
>>
>> <RM_20_BIC.ll>
>> <RM_112_ORN.ll>
>>
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>

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