[llvm] [AArch64][CostModel] Alter sdiv/srem cost where the divisor is constant (PR #123552)

[David Green via llvm-commits]

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@@ -287,29 +287,29 @@ define void @udiv_uniform() {
 
 define void @sdiv_const() {
 ; CHECK-LABEL: 'sdiv_const'
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 10 for instruction: %I128 = sdiv i128 undef, 7
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 7 for instruction: %I64 = sdiv i64 undef, 7
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 28 for instruction: %V2i64 = sdiv <2 x i64> undef, <i64 6, i64 7>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 56 for instruction: %V4i64 = sdiv <4 x i64> undef, <i64 4, i64 5, i64 6, i64 7>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 112 for instruction: %V8i64 = sdiv <8 x i64> undef, <i64 4, i64 5, i64 6, i64 7, i64 8, i64 9, i64 10, i64 11>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %I32 = sdiv i32 undef, 7
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 28 for instruction: %V2i32 = sdiv <2 x i32> undef, <i32 4, i32 5>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 48 for instruction: %V4i32 = sdiv <4 x i32> undef, <i32 4, i32 5, i32 6, i32 7>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 96 for instruction: %V8i32 = sdiv <8 x i32> undef, <i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 192 for instruction: %V16i32 = sdiv <16 x i32> undef, <i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15, i32 16, i32 17, i32 18, i32 19>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %I16 = sdiv i16 undef, 7
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 28 for instruction: %V2i16 = sdiv <2 x i16> undef, <i16 4, i16 5>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 48 for instruction: %V4i16 = sdiv <4 x i16> undef, <i16 4, i16 5, i16 6, i16 7>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 88 for instruction: %V8i16 = sdiv <8 x i16> undef, <i16 4, i16 5, i16 6, i16 7, i16 8, i16 9, i16 10, i16 11>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 176 for instruction: %V16i16 = sdiv <16 x i16> undef, <i16 4, i16 5, i16 6, i16 7, i16 8, i16 9, i16 10, i16 11, i16 12, i16 13, i16 14, i16 15, i16 16, i16 17, i16 18, i16 19>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 352 for instruction: %V32i16 = sdiv <32 x i16> undef, <i16 4, i16 5, i16 6, i16 7, i16 8, i16 9, i16 10, i16 11, i16 12, i16 13, i16 14, i16 15, i16 16, i16 17, i16 18, i16 19, i16 4, i16 5, i16 6, i16 7, i16 8, i16 9, i16 10, i16 11, i16 12, i16 13, i16 14, i16 15, i16 16, i16 17, i16 18, i16 19>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %I8 = sdiv i8 undef, 7
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 28 for instruction: %V2i8 = sdiv <2 x i8> undef, <i8 4, i8 5>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 48 for instruction: %V4i8 = sdiv <4 x i8> undef, <i8 4, i8 5, i8 6, i8 7>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 88 for instruction: %V8i8 = sdiv <8 x i8> undef, <i8 4, i8 5, i8 6, i8 7, i8 8, i8 9, i8 10, i8 11>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 168 for instruction: %V16i8 = sdiv <16 x i8> undef, <i8 4, i8 5, i8 6, i8 7, i8 8, i8 9, i8 10, i8 11, i8 12, i8 13, i8 14, i8 15, i8 16, i8 17, i8 18, i8 19>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 336 for instruction: %V32i8 = sdiv <32 x i8> undef, <i8 4, i8 5, i8 6, i8 7, i8 8, i8 9, i8 10, i8 11, i8 12, i8 13, i8 14, i8 15, i8 16, i8 17, i8 18, i8 19, i8 4, i8 5, i8 6, i8 7, i8 8, i8 9, i8 10, i8 11, i8 12, i8 13, i8 14, i8 15, i8 16, i8 17, i8 18, i8 19>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 672 for instruction: %V64i8 = sdiv <64 x i8> undef, <i8 4, i8 5, i8 6, i8 7, i8 8, i8 9, i8 10, i8 11, i8 12, i8 13, i8 14, i8 15, i8 16, i8 17, i8 18, i8 19, i8 4, i8 5, i8 6, i8 7, i8 8, i8 9, i8 10, i8 11, i8 12, i8 13, i8 14, i8 15, i8 16, i8 17, i8 18, i8 19, i8 4, i8 5, i8 6, i8 7, i8 8, i8 9, i8 10, i8 11, i8 12, i8 13, i8 14, i8 15, i8 16, i8 17, i8 18, i8 19, i8 4, i8 5, i8 6, i8 7, i8 8, i8 9, i8 10, i8 11, i8 12, i8 13, i8 14, i8 15, i8 16, i8 17, i8 18, i8 19>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 8 for instruction: %I128 = sdiv i128 undef, 7
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davemgreen wrote:

The getTypeLegalizationCost works well for vector types / certain operations, but is a little less helpful for others. It should return (2, MVT::i64}, but the 2 isn't necessarily very meaningful for a div or mul operation that will go through a lib call.

https://github.com/llvm/llvm-project/pull/123552