[llvm-dev] Store lowering -> Cannot select FrameIndex.

[Krzysztof Parzyszek via llvm-dev]

You cannot discard it, you need to provide some form of converting it 
into the address of the given stack slot: a selection pattern, custom 
selection, etc.

-Krzysztof


On 9/20/2017 10:14 AM, Dominique Torette via llvm-dev wrote:
> Hi,
> 
> I’m try to lower the store LLVM-IR instruction as per the following LLVM 
> IR program:
> 
> *** IR Dump After Module Verifier ***
> 
> define void @storeloadi32() {
> 
>    %ptr = alloca i32
> 
>    store volatile i32 12, i32* %ptr
> 
>    ret void
> 
> }
> 
> The target instruction is associated to the store like this:
> 
>              def       MOVSUTO_A_iSLr : CLPFPU_A_iSLr<0b1000001101,
> 
>                                                  (ins 
> IMM32Operand:$ImmA, FPUaRegisterOperand:$RegB),
> 
>                                                  (outs ),
> 
>                                                  [],
> 
>                                                  "movsuto_a\t$ImmA,$RegB",
> 
> [(store i32:$ImmA, i16:$RegB)],NoItinerary> {
> 
> The selection DAG seems to be correct, but a FrameIndex of 0 as been 
> introduced :
> 
> Optimized legalized selection DAG: BB#0 'storeloadi32:'
> 
> SelectionDAG has 6 nodes:
> 
>        t0: ch = EntryToken
> 
>      t5: ch = store<Volatile ST4[%ptr]> t0, Constant:i32<12>, 
> FrameIndex:i16<0>, undef:i16
> 
>    t6: ch = CLPISD::RET_FLAG t5
> 
> ISEL: Starting pattern match on root node: t5: ch = store<Volatile 
> ST4[%ptr]> t0, Constant:i32<12>, FrameIndex:i16<0>, undef:i16
> 
> The lowering correctly catches the store and morphs to right 
> MOVSUTO_A_iSLr MC instruction:
> 
>    Initial Opcode index to 331
> 
>    Skipped scope entry (due to false predicate) at index 339, continuing 
> at 354
> 
> Morphed node: t5: ch = MOVSUTO_A_iSLr<Mem:Volatile ST4[%ptr]> 
> Constant:i32<12>, FrameIndex:i16<0>, t0
> 
> ISEL: Match complete!
> 
> Then instruction selection try to lower the FrameIndex node !!! This failed…
> 
> ISEL: Starting pattern match on root node: t2: i16 = FrameIndex<0>
> 
>    Initial Opcode index to 0
> 
>    Match failed at index 0
> 
> LLVM ERROR: Cannot select: t2: i16 = FrameIndex<0>
> 
> How to discard this FrameIndex<0> ?
> 
> 
> 
> 
> 
> http://www.spacebel.be/wp-content/uploads/2011/06/image-sign-sbp.jpg
> 
> *Dominique Torette*
> System Architect
> Rue des Chasseurs Ardennais - Liège Science Park - B-4031 Angleur
> Tel: +32 (0) 4 361 81 11 - Fax: +32 (0) 4 361 81 20
> www.spacebel.be <http://www.spacebel.be/>
> 
> 
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