[llvm] [RISCV] Tune flag for fast vrgather.vv (PR #124664)

[Petr Penzin via llvm-commits]

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@@ -44,6 +46,24 @@ define void @general_permute_single_source() {
 ; SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %v8f32 = shufflevector <8 x float> undef, <8 x float> undef, <8 x i32> <i32 7, i32 6, i32 5, i32 5, i32 3, i32 2, i32 1, i32 0>
 ; SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %v4f64 = shufflevector <4 x double> undef, <4 x double> undef, <4 x i32> <i32 3, i32 2, i32 3, i32 0>
 ; SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: ret void
+;
+; FAST-VRG-LABEL: 'general_permute_single_source'
+; FAST-VRG-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %v4i8 = shufflevector <4 x i8> undef, <4 x i8> undef, <4 x i32> <i32 2, i32 3, i32 1, i32 0>
+; FAST-VRG-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %v8i8 = shufflevector <8 x i8> undef, <8 x i8> undef, <8 x i32> <i32 7, i32 5, i32 5, i32 5, i32 3, i32 2, i32 1, i32 0>
+; FAST-VRG-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %v16i8 = shufflevector <16 x i8> undef, <16 x i8> undef, <16 x i32> <i32 15, i32 14, i32 13, i32 12, i32 11, i32 10, i32 9, i32 9, i32 6, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
+; FAST-VRG-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %v4i16 = shufflevector <4 x i16> undef, <4 x i16> undef, <4 x i32> <i32 3, i32 2, i32 2, i32 0>
+; FAST-VRG-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %v8i16 = shufflevector <8 x i16> undef, <8 x i16> undef, <8 x i32> <i32 7, i32 6, i32 5, i32 5, i32 5, i32 2, i32 1, i32 0>
+; FAST-VRG-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %v16i16 = shufflevector <16 x i16> undef, <16 x i16> undef, <16 x i32> <i32 15, i32 14, i32 13, i32 11, i32 11, i32 11, i32 9, i32 8, i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
+; FAST-VRG-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %v4i32 = shufflevector <4 x i32> undef, <4 x i32> undef, <4 x i32> <i32 3, i32 2, i32 2, i32 0>
+; FAST-VRG-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %v8i32 = shufflevector <8 x i32> undef, <8 x i32> undef, <8 x i32> <i32 7, i32 4, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
+; FAST-VRG-NEXT:  Cost Model: Found an estimated cost of 5 for instruction: %v4i64 = shufflevector <4 x i64> undef, <4 x i64> undef, <4 x i32> <i32 3, i32 1, i32 1, i32 0>
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ppenzin wrote:

Because IndexCost is cheaper by one, same before this patch.

https://github.com/llvm/llvm-project/pull/124664