[llvm] [LV] Ignore some costs when loop gets fully unrolled (PR #106699)

[Igor Kirillov via llvm-commits]

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@@ -185,34 +185,26 @@ define void @trip8_i8(ptr noalias nocapture noundef %dst, ptr noalias nocapture
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    br i1 false, label [[SCALAR_PH:%.*]], label [[VECTOR_PH:%.*]]
 ; CHECK:       vector.ph:
-; CHECK-NEXT:    [[TMP0:%.*]] = call i64 @llvm.vscale.i64()
-; CHECK-NEXT:    [[TMP1:%.*]] = mul i64 [[TMP0]], 4
-; CHECK-NEXT:    [[TMP4:%.*]] = sub i64 [[TMP1]], 1
-; CHECK-NEXT:    [[N_RND_UP:%.*]] = add i64 8, [[TMP4]]
-; CHECK-NEXT:    [[N_MOD_VF:%.*]] = urem i64 [[N_RND_UP]], [[TMP1]]
-; CHECK-NEXT:    [[N_VEC:%.*]] = sub i64 [[N_RND_UP]], [[N_MOD_VF]]
-; CHECK-NEXT:    [[TMP5:%.*]] = call i64 @llvm.vscale.i64()
-; CHECK-NEXT:    [[TMP6:%.*]] = mul i64 [[TMP5]], 4
 ; CHECK-NEXT:    br label [[VECTOR_BODY:%.*]]
 ; CHECK:       vector.body:
 ; CHECK-NEXT:    [[INDEX:%.*]] = phi i64 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
 ; CHECK-NEXT:    [[TMP7:%.*]] = add i64 [[INDEX]], 0
-; CHECK-NEXT:    [[ACTIVE_LANE_MASK:%.*]] = call <vscale x 4 x i1> @llvm.get.active.lane.mask.nxv4i1.i64(i64 [[TMP7]], i64 8)
+; CHECK-NEXT:    [[ACTIVE_LANE_MASK:%.*]] = call <8 x i1> @llvm.get.active.lane.mask.v8i1.i64(i64 [[TMP7]], i64 8)
 ; CHECK-NEXT:    [[TMP8:%.*]] = getelementptr inbounds i8, ptr [[SRC:%.*]], i64 [[TMP7]]
 ; CHECK-NEXT:    [[TMP9:%.*]] = getelementptr inbounds i8, ptr [[TMP8]], i32 0
-; CHECK-NEXT:    [[WIDE_MASKED_LOAD:%.*]] = call <vscale x 4 x i8> @llvm.masked.load.nxv4i8.p0(ptr [[TMP9]], i32 1, <vscale x 4 x i1> [[ACTIVE_LANE_MASK]], <vscale x 4 x i8> poison)
-; CHECK-NEXT:    [[TMP10:%.*]] = shl <vscale x 4 x i8> [[WIDE_MASKED_LOAD]], shufflevector (<vscale x 4 x i8> insertelement (<vscale x 4 x i8> poison, i8 1, i64 0), <vscale x 4 x i8> poison, <vscale x 4 x i32> zeroinitializer)
+; CHECK-NEXT:    [[WIDE_MASKED_LOAD:%.*]] = call <8 x i8> @llvm.masked.load.v8i8.p0(ptr [[TMP9]], i32 1, <8 x i1> [[ACTIVE_LANE_MASK]], <8 x i8> poison)
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igogo-x86 wrote:

Yep, that's also bothering me. But where I'm adding this code, I can't see how to understand if scalable vectorisation is available and whether it would be tail-folded or not.

https://github.com/llvm/llvm-project/pull/106699