[llvm-dev] LICM doesn't work for IntrReadMem intrinsic function

[Xiangyang Guo via llvm-dev]

Opps, the IR is

  %2 = call i32 @llvm.foo(i32 %a, i32 1)
  %3 = call i32 @_Z5func2ii(i32 %b, i32 %2)

2015-12-01 15:59 GMT-05:00 Xiangyang Guo <eceguo at gmail.com>:

> Actually, no such information is attached to "func2".
>
> For the following IR, if "func2" can only access the memory related to the
> first parameter "%b" and it will not change the value related to second
> parameter "%2", do you know how I can tell LLVM these information? And if I
> can do this, probably the LICM will work for llvm.foo? Thanks
>
>  %2 = call i32 @llvm.foo(i32 %a, i32 1)
>  %3 = call i32 @_Z5func2ii(i32 %b, i32 %2)
>
> 2015-12-01 15:51 GMT-05:00 Tim Northover <t.p.northover at gmail.com>:
>
>> On 1 December 2015 at 12:33, Xiangyang Guo via llvm-dev
>> <llvm-dev at lists.llvm.org> wrote:
>> > if I have the following IR, LICM doesn't work again, even if I use
>> > '-loop-rotate' firstly. In this IR, the return value of intrinsic
>> function
>> > "foo" is used by another function "func2" as parameter.  However, for
>> the
>> > intrinsic function "foo", the parameters are still loop invariant. Do
>> you
>> > know why this happens? Thanks a lot.
>>
>> Is there anything telling LLVM that func2 won't write to memory and
>> change the value returned by llvm.foo?
>>
>> Cheers.
>>
>> Tim.
>>
>
>
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