[llvm] r181927 - Implement PPC counter loops as a late IR-level pass

[Hal Finkel]

----- Original Message -----
> Hal Finkel <hfinkel at anl.gov> wrote on 16.05.2013 18:55:06:
> 
> > This should be fixed by r182023, please verify.
> 
> Not, it isn't fixed, unfortunately.
> 
> Here's the reduced test case I'm using:
> 
> target datalayout =
> "E-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v128:128:128-n32"
> target triple = "powerpc-unknown-linux-gnu"
> 
> @init_value = global double 1.000000e+00, align 8
> @data64 = global [8000 x i64] zeroinitializer, align 8
> 
> define i32 @main(i32 %argc, i8** nocapture %argv) {
> entry:
>   %0 = load double* @init_value, align 8
>   %conv = fptosi double %0 to i64
>   %broadcast.splatinsert.i = insertelement <2 x i64> undef, i64
>   %conv, i32
> 0
>   %broadcast.splat.i = shufflevector <2 x i64>
>   %broadcast.splatinsert.i, <2
> x i64> undef, <2 x i32> zeroinitializer
>   br label %vector.body.i
> 
> vector.body.i:                                    ; preds =
> %vector.body.i,
> %entry
>   %index.i = phi i32 [ 0, %entry ], [ %index.next.i, %vector.body.i ]
>   %next.gep.i = getelementptr [8000 x i64]* @data64, i32 0, i32
>   %index.i
>   %1 = bitcast i64* %next.gep.i to <2 x i64>*
>   store <2 x i64> %broadcast.splat.i, <2 x i64>* %1, align 8
>   %next.gep.sum24.i = or i32 %index.i, 2
>   %2 = getelementptr [8000 x i64]* @data64, i32 0, i32
>   %next.gep.sum24.i
>   %3 = bitcast i64* %2 to <2 x i64>*
>   store <2 x i64> %broadcast.splat.i, <2 x i64>* %3, align 8
>   %index.next.i = add i32 %index.i, 4
>   %4 = icmp eq i32 %index.next.i, 8000
>   br i1 %4, label %_Z4fillIPxxEvT_S1_T0_.exit, label %vector.body.i
> 
> _Z4fillIPxxEvT_S1_T0_.exit:                       ; preds =
> %vector.body.i
>   ret i32 0
> }
> 
> You'll need to use -mcpu=ppc to actually get the helper routine call.
> 
> Note that in this instance, the fptosi isn't even in the loop in the
> first
> place, but in the block before it!
> 
> After the PPCCtr pass, we have:
> 
> entry:
>   %0 = load double* @init_value, align 8
>   %conv = fptosi double %0 to i64
>   %broadcast.splatinsert.i = insertelement <2 x i64> undef, i64
>   %conv, i32
> 0
>   %broadcast.splat.i = shufflevector <2 x i64>
>   %broadcast.splatinsert.i, <2
> x i64> undef, <2 x i32> zeroinitializer
>   call void @llvm.ppc.mtctr.i32(i32 2000)
>   br label %vector.body.i
> 
> so the load of CTR is *after* the fptosi, but apparently this doesn't
> count
> as a dependency for SelectionDAG, as after selection we get:

Thanks for the test case! I agree with Chris that a more robust solution should likely be designed. Hopefully r182045 will fix this for now.

 -Hal

> 
>         ADJCALLSTACKDOWN 8, %R1<imp-def,dead>, %R1<imp-use>
>         MTCTRse %vreg10<kill>, %CTR<imp-def,dead>; GPRC:%vreg10
>         %F1<def> = COPY %vreg11; F8RC:%vreg11
>         BL <es:__fixdfdi>, <regmask>, %LR<imp-def,dead>,
>         %RM<imp-use>,
> %F1<imp-use>, %R1<imp-def>, %R3<imp-def>, %R4<imp-def>
>         ADJCALLSTACKUP 8, 0, %R1<imp-def,dead>, %R1<imp-use>
> 
> Bye,
> Ulrich
> 
>