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llvm-project/llvm/test/CodeGen/Thumb2/LowOverheadLoops/vector-unroll.ll
David Green b2ac9681a7 [ARM] Alter t2DoLoopStart to define lr 
This changes the definition of t2DoLoopStart from
t2DoLoopStart rGPR
to
GPRlr = t2DoLoopStart rGPR

This will hopefully mean that low overhead loops are more tied together,
and we can more reliably generate loops without reverting or being at
the whims of the register allocator.

This is a fairly simple change in itself, but leads to a number of other
required alterations.

 - The hardware loop pass, if UsePhi is set, now generates loops of the
   form:
       %start = llvm.start.loop.iterations(%N)
     loop:
       %p = phi [%start], [%dec]
       %dec = llvm.loop.decrement.reg(%p, 1)
       %c = icmp ne %dec, 0
       br %c, loop, exit
 - For this a new llvm.start.loop.iterations intrinsic was added, identical
   to llvm.set.loop.iterations but produces a value as seen above, gluing
   the loop together more through def-use chains.
 - This new instrinsic conceptually produces the same output as input,
   which is taught to SCEV so that the checks in MVETailPredication are not
   affected.
 - Some minor changes are needed to the ARMLowOverheadLoop pass, but it has
   been left mostly as before. We should now more reliably be able to tell
   that the t2DoLoopStart is correct without having to prove it, but
   t2WhileLoopStart and tail-predicated loops will remain the same.
 - And all the tests have been updated. There are a lot of them!

This patch on it's own might cause more trouble that it helps, with more
tail-predicated loops being reverted, but some additional patches can
hopefully improve upon that to get to something that is better overall.

Differential Revision: https://reviews.llvm.org/D89881
2020-11-10 15:57:58 +00:00

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; RUN: opt -mtriple=thumbv8.1m.main -mve-tail-predication -tail-predication=enabled -mattr=+mve,+lob %s -S -o - | FileCheck %s
; TODO: The unrolled pattern is preventing the transform
; CHECK-LABEL: mul_v16i8_unroll
; CHECK-NOT: call i32 @llvm.arm.vcpt
define void @mul_v16i8_unroll(i8* noalias nocapture readonly %a, i8* noalias nocapture readonly %b, i8* noalias nocapture %c, i32 %N) {
entry:
%cmp8 = icmp eq i32 %N, 0
%tmp8 = add i32 %N, 15
%tmp9 = lshr i32 %tmp8, 4
%tmp10 = shl nuw i32 %tmp9, 4
%tmp11 = add i32 %tmp10, -16
%tmp12 = lshr i32 %tmp11, 4
%tmp13 = add nuw nsw i32 %tmp12, 1
br i1 %cmp8, label %for.cond.cleanup, label %vector.ph
vector.ph: ; preds = %entry
%trip.count.minus.1 = add i32 %N, -1
%broadcast.splatinsert10 = insertelement <16 x i32> undef, i32 %trip.count.minus.1, i32 0
%broadcast.splat11 = shufflevector <16 x i32> %broadcast.splatinsert10, <16 x i32> undef, <16 x i32> zeroinitializer
%xtraiter = and i32 %tmp13, 1
%0 = icmp ult i32 %tmp12, 1
br i1 %0, label %for.cond.cleanup.loopexit.unr-lcssa, label %vector.ph.new
vector.ph.new: ; preds = %vector.ph
%start = call i32 @llvm.start.loop.iterations.i32(i32 %tmp13)
%unroll_iter = sub i32 %tmp13, %xtraiter
br label %vector.body
vector.body: ; preds = %vector.body, %vector.ph.new
%index = phi i32 [ 0, %vector.ph.new ], [ %index.next.1, %vector.body ]
%niter = phi i32 [ %unroll_iter, %vector.ph.new ], [ %niter.nsub.1, %vector.body ]
%broadcast.splatinsert = insertelement <16 x i32> undef, i32 %index, i32 0
%broadcast.splat = shufflevector <16 x i32> %broadcast.splatinsert, <16 x i32> undef, <16 x i32> zeroinitializer
%induction = add <16 x i32> %broadcast.splat, <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
%tmp = getelementptr inbounds i8, i8* %a, i32 %index
%tmp1 = icmp ule <16 x i32> %induction, %broadcast.splat11
%tmp2 = bitcast i8* %tmp to <16 x i8>*
%wide.masked.load = tail call <16 x i8> @llvm.masked.load.v16i8.p0v16i8(<16 x i8>* %tmp2, i32 4, <16 x i1> %tmp1, <16 x i8> undef)
%tmp3 = getelementptr inbounds i8, i8* %b, i32 %index
%tmp4 = bitcast i8* %tmp3 to <16 x i8>*
%wide.masked.load2 = tail call <16 x i8> @llvm.masked.load.v16i8.p0v16i8(<16 x i8>* %tmp4, i32 4, <16 x i1> %tmp1, <16 x i8> undef)
%mul = mul nsw <16 x i8> %wide.masked.load2, %wide.masked.load
%tmp6 = getelementptr inbounds i8, i8* %c, i32 %index
%tmp7 = bitcast i8* %tmp6 to <16 x i8>*
tail call void @llvm.masked.store.v16i8.p0v16i8(<16 x i8> %mul, <16 x i8>* %tmp7, i32 4, <16 x i1> %tmp1)
%index.next = add nuw nsw i32 %index, 16
%niter.nsub = sub i32 %niter, 1
%broadcast.splatinsert.1 = insertelement <16 x i32> undef, i32 %index.next, i32 0
%broadcast.splat.1 = shufflevector <16 x i32> %broadcast.splatinsert.1, <16 x i32> undef, <16 x i32> zeroinitializer
%induction.1 = add <16 x i32> %broadcast.splat.1, <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
%tmp.1 = getelementptr inbounds i8, i8* %a, i32 %index.next
%tmp1.1 = icmp ule <16 x i32> %induction.1, %broadcast.splat11
%tmp2.1 = bitcast i8* %tmp.1 to <16 x i8>*
%wide.masked.load.1 = tail call <16 x i8> @llvm.masked.load.v16i8.p0v16i8(<16 x i8>* %tmp2.1, i32 4, <16 x i1> %tmp1.1, <16 x i8> undef)
%tmp3.1 = getelementptr inbounds i8, i8* %b, i32 %index.next
%tmp4.1 = bitcast i8* %tmp3.1 to <16 x i8>*
%wide.masked.load2.1 = tail call <16 x i8> @llvm.masked.load.v16i8.p0v16i8(<16 x i8>* %tmp4.1, i32 4, <16 x i1> %tmp1.1, <16 x i8> undef)
%mul.1 = mul nsw <16 x i8> %wide.masked.load2.1, %wide.masked.load.1
%tmp6.1 = getelementptr inbounds i8, i8* %c, i32 %index.next
%tmp7.1 = bitcast i8* %tmp6.1 to <16 x i8>*
tail call void @llvm.masked.store.v16i8.p0v16i8(<16 x i8> %mul.1, <16 x i8>* %tmp7.1, i32 4, <16 x i1> %tmp1.1)
%index.next.1 = add i32 %index.next, 16
%niter.nsub.1 = call i32 @llvm.loop.decrement.reg.i32.i32.i32(i32 %niter.nsub, i32 1)
%niter.ncmp.1 = icmp ne i32 %niter.nsub.1, 0
br i1 %niter.ncmp.1, label %vector.body, label %for.cond.cleanup.loopexit.unr-lcssa.loopexit
for.cond.cleanup.loopexit.unr-lcssa.loopexit: ; preds = %vector.body
%index.unr.ph = phi i32 [ %index.next.1, %vector.body ]
%tmp14.unr.ph = phi i32 [ -2, %vector.body ]
br label %for.cond.cleanup.loopexit.unr-lcssa
for.cond.cleanup.loopexit.unr-lcssa: ; preds = %for.cond.cleanup.loopexit.unr-lcssa.loopexit, %vector.ph
%index.unr = phi i32 [ 0, %vector.ph ], [ %index.unr.ph, %for.cond.cleanup.loopexit.unr-lcssa.loopexit ]
%tmp14.unr = phi i32 [ %tmp13, %vector.ph ], [ %tmp14.unr.ph, %for.cond.cleanup.loopexit.unr-lcssa.loopexit ]
%lcmp.mod = icmp ne i32 %xtraiter, 0
br i1 %lcmp.mod, label %vector.body.epil.preheader, label %for.cond.cleanup.loopexit
vector.body.epil.preheader: ; preds = %for.cond.cleanup.loopexit.unr-lcssa
br label %vector.body.epil
vector.body.epil: ; preds = %vector.body.epil.preheader
%index.epil = phi i32 [ %index.unr, %vector.body.epil.preheader ]
%tmp14.epil = phi i32 [ %tmp14.unr, %vector.body.epil.preheader ]
%broadcast.splatinsert.epil = insertelement <16 x i32> undef, i32 %index.epil, i32 0
%broadcast.splat.epil = shufflevector <16 x i32> %broadcast.splatinsert.epil, <16 x i32> undef, <16 x i32> zeroinitializer
%induction.epil = add <16 x i32> %broadcast.splat.epil, <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
%tmp.epil = getelementptr inbounds i8, i8* %a, i32 %index.epil
%tmp1.epil = icmp ule <16 x i32> %induction.epil, %broadcast.splat11
%tmp2.epil = bitcast i8* %tmp.epil to <16 x i8>*
%wide.masked.load.epil = tail call <16 x i8> @llvm.masked.load.v16i8.p0v16i8(<16 x i8>* %tmp2.epil, i32 4, <16 x i1> %tmp1.epil, <16 x i8> undef)
%tmp3.epil = getelementptr inbounds i8, i8* %b, i32 %index.epil
%tmp4.epil = bitcast i8* %tmp3.epil to <16 x i8>*
%wide.masked.load2.epil = tail call <16 x i8> @llvm.masked.load.v16i8.p0v16i8(<16 x i8>* %tmp4.epil, i32 4, <16 x i1> %tmp1.epil, <16 x i8> undef)
%mul.epil = mul nsw <16 x i8> %wide.masked.load2.epil, %wide.masked.load.epil
%tmp6.epil = getelementptr inbounds i8, i8* %c, i32 %index.epil
%tmp7.epil = bitcast i8* %tmp6.epil to <16 x i8>*
tail call void @llvm.masked.store.v16i8.p0v16i8(<16 x i8> %mul.epil, <16 x i8>* %tmp7.epil, i32 4, <16 x i1> %tmp1.epil)
%index.next.epil = add i32 %index.epil, 16
%tmp15.epil = add nuw nsw i32 %tmp14.epil, -1
%tmp16.epil = icmp ne i32 %tmp15.epil, 0
br label %for.cond.cleanup.loopexit.epilog-lcssa
for.cond.cleanup.loopexit.epilog-lcssa: ; preds = %vector.body.epil
br label %for.cond.cleanup.loopexit
for.cond.cleanup.loopexit: ; preds = %for.cond.cleanup.loopexit.unr-lcssa, %for.cond.cleanup.loopexit.epilog-lcssa
br label %for.cond.cleanup
for.cond.cleanup: ; preds = %for.cond.cleanup.loopexit, %entry
ret void
}
declare <16 x i8> @llvm.masked.load.v16i8.p0v16i8(<16 x i8>*, i32 immarg, <16 x i1>, <16 x i8>) #1
declare void @llvm.masked.store.v16i8.p0v16i8(<16 x i8>, <16 x i8>*, i32 immarg, <16 x i1>) #2
declare i32 @llvm.start.loop.iterations.i32(i32) #3
declare i32 @llvm.loop.decrement.reg.i32.i32.i32(i32, i32) #3
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