[llvm] [LV][EVL] Support reduction idioms using tail folding with EVL. (PR #90184)

[Florian Hahn via llvm-commits]

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@@ -0,0 +1,2253 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -passes=loop-vectorize \
+; RUN: -force-tail-folding-style=data-with-evl \
+; RUN: -prefer-predicate-over-epilogue=predicate-dont-vectorize \
+; RUN: -mtriple=riscv64 -mattr=+v,+f -S < %s| FileCheck %s --check-prefix=IF-EVL
+
+; RUN: opt -passes=loop-vectorize \
+; RUN: -force-tail-folding-style=none \
+; RUN: -prefer-predicate-over-epilogue=predicate-else-scalar-epilogue \
+; RUN: -mtriple=riscv64 -mattr=+v,+f -S < %s| FileCheck %s --check-prefix=NO-VP
+
+define i32 @add(ptr %a, i64 %n, i32 %start) {
+; IF-EVL-LABEL: @add(
+; IF-EVL-NEXT:  entry:
+; IF-EVL-NEXT:    [[TMP0:%.*]] = sub i64 -1, [[N:%.*]]
+; IF-EVL-NEXT:    [[TMP1:%.*]] = call i64 @llvm.vscale.i64()
+; IF-EVL-NEXT:    [[TMP2:%.*]] = mul i64 [[TMP1]], 4
+; IF-EVL-NEXT:    [[TMP3:%.*]] = icmp ult i64 [[TMP0]], [[TMP2]]
+; IF-EVL-NEXT:    br i1 [[TMP3]], label [[SCALAR_PH:%.*]], label [[VECTOR_PH:%.*]]
+; IF-EVL:       vector.ph:
+; IF-EVL-NEXT:    [[TMP4:%.*]] = call i64 @llvm.vscale.i64()
+; IF-EVL-NEXT:    [[TMP5:%.*]] = mul i64 [[TMP4]], 4
+; IF-EVL-NEXT:    [[TMP6:%.*]] = call i64 @llvm.vscale.i64()
+; IF-EVL-NEXT:    [[TMP7:%.*]] = mul i64 [[TMP6]], 4
+; IF-EVL-NEXT:    [[TMP8:%.*]] = sub i64 [[TMP7]], 1
+; IF-EVL-NEXT:    [[N_RND_UP:%.*]] = add i64 [[N]], [[TMP8]]
+; IF-EVL-NEXT:    [[N_MOD_VF:%.*]] = urem i64 [[N_RND_UP]], [[TMP5]]
+; IF-EVL-NEXT:    [[N_VEC:%.*]] = sub i64 [[N_RND_UP]], [[N_MOD_VF]]
+; IF-EVL-NEXT:    [[TRIP_COUNT_MINUS_1:%.*]] = sub i64 [[N]], 1
+; IF-EVL-NEXT:    [[TMP9:%.*]] = call i64 @llvm.vscale.i64()
+; IF-EVL-NEXT:    [[TMP10:%.*]] = mul i64 [[TMP9]], 4
+; IF-EVL-NEXT:    [[TMP11:%.*]] = insertelement <vscale x 4 x i32> zeroinitializer, i32 [[START:%.*]], i32 0
+; IF-EVL-NEXT:    [[BROADCAST_SPLATINSERT1:%.*]] = insertelement <vscale x 4 x i64> poison, i64 [[TRIP_COUNT_MINUS_1]], i64 0
+; IF-EVL-NEXT:    [[BROADCAST_SPLAT2:%.*]] = shufflevector <vscale x 4 x i64> [[BROADCAST_SPLATINSERT1]], <vscale x 4 x i64> poison, <vscale x 4 x i32> zeroinitializer
+; IF-EVL-NEXT:    br label [[VECTOR_BODY:%.*]]
+; IF-EVL:       vector.body:
+; IF-EVL-NEXT:    [[INDEX:%.*]] = phi i64 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
+; IF-EVL-NEXT:    [[EVL_BASED_IV:%.*]] = phi i64 [ 0, [[VECTOR_PH]] ], [ [[INDEX_EVL_NEXT:%.*]], [[VECTOR_BODY]] ]
+; IF-EVL-NEXT:    [[VEC_PHI:%.*]] = phi <vscale x 4 x i32> [ [[TMP11]], [[VECTOR_PH]] ], [ [[TMP20:%.*]], [[VECTOR_BODY]] ]
+; IF-EVL-NEXT:    [[TMP12:%.*]] = sub i64 [[N]], [[EVL_BASED_IV]]
+; IF-EVL-NEXT:    [[TMP13:%.*]] = call i32 @llvm.experimental.get.vector.length.i64(i64 [[TMP12]], i32 4, i1 true)
+; IF-EVL-NEXT:    [[TMP14:%.*]] = add i64 [[EVL_BASED_IV]], 0
+; IF-EVL-NEXT:    [[BROADCAST_SPLATINSERT:%.*]] = insertelement <vscale x 4 x i64> poison, i64 [[EVL_BASED_IV]], i64 0
+; IF-EVL-NEXT:    [[BROADCAST_SPLAT:%.*]] = shufflevector <vscale x 4 x i64> [[BROADCAST_SPLATINSERT]], <vscale x 4 x i64> poison, <vscale x 4 x i32> zeroinitializer
+; IF-EVL-NEXT:    [[TMP15:%.*]] = call <vscale x 4 x i64> @llvm.experimental.stepvector.nxv4i64()
+; IF-EVL-NEXT:    [[TMP16:%.*]] = add <vscale x 4 x i64> zeroinitializer, [[TMP15]]
+; IF-EVL-NEXT:    [[VEC_IV:%.*]] = add <vscale x 4 x i64> [[BROADCAST_SPLAT]], [[TMP16]]
+; IF-EVL-NEXT:    [[TMP17:%.*]] = icmp ule <vscale x 4 x i64> [[VEC_IV]], [[BROADCAST_SPLAT2]]
+; IF-EVL-NEXT:    [[TMP18:%.*]] = getelementptr inbounds i32, ptr [[A:%.*]], i64 [[TMP14]]
+; IF-EVL-NEXT:    [[TMP19:%.*]] = getelementptr inbounds i32, ptr [[TMP18]], i32 0
+; IF-EVL-NEXT:    [[VP_OP_LOAD:%.*]] = call <vscale x 4 x i32> @llvm.vp.load.nxv4i32.p0(ptr align 4 [[TMP19]], <vscale x 4 x i1> shufflevector (<vscale x 4 x i1> insertelement (<vscale x 4 x i1> poison, i1 true, i64 0), <vscale x 4 x i1> poison, <vscale x 4 x i32> zeroinitializer), i32 [[TMP13]])
+; IF-EVL-NEXT:    [[TMP20]] = add <vscale x 4 x i32> [[VP_OP_LOAD]], [[VEC_PHI]]
----------------
fhahn wrote:

Ah I see. In that case, to avoid needing to pull in another patch, can we bail out for any operation that use something other than the header mask, so we can land this change, followed by https://github.com/llvm/llvm-project/pull/95368 ?

https://github.com/llvm/llvm-project/pull/90184