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Merged
merged 1 commit into from
Jan 18, 2024
Merged

[RISCV] Adjust select shuffle cost to reflect mask creation cost #77963

merged 1 commit into from
Jan 18, 2024

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preames
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@preames preames commented Jan 12, 2024

This is inspired by #77342 (review), and is split off of same with some differences in style.

A select is a vmerge.vv with the additional cost of materializing the bitmask vector in a vreg. All masks fit within a single vector register (e8 + m8 is the worst case), and thus our worst case cost should be roughly 3 (2 scalar to produce the address, one vector load op). Given most shuffles are small, and the mask will be instead produced by LUI/ADDI + vmv.s.x or ADDI + vmv.s.x, using 2 as the default seems quite reasonable. At worst, we're not going to be off by much.

The prior lowering scaled the cost of the bitmask with LMUL, which I don't understand. At m1 it did use the same base cost of 2. (@lukel97 You wrote the original code here, anything I'm missing here?)

@preames
[RISCV] Adjust select shuffle cost to reflect mask creation cost
e886bb3 
This is inspired by llvm#77342 (review), and is split off of same with some differences in style.

A select is a vmerge.vv with the additional cost of materializing the bitmask vector in a vreg.  All masks fit within a single vector register (e8 + m8 is the worst case), and thus our worst case cost should be roughly 3 (2 scalar to produce the address, one vector load op).  Given most shuffles are small, and the mask will be instead produced by LUI/ADDI + vmv.s.x or ADDI + vmv.s.x, using 2 as the default seems quite reasonable.  At worst, we're not going to be off by much.

The prior lowering scaled the cost of the bitmask with LMUL, which I don't understand.  At m1 it did use the same base cost of 2.
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llvmbot commented Jan 12, 2024 •
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@llvm/pr-subscribers-backend-risc-v

@llvm/pr-subscribers-llvm-analysis

Author: Philip Reames (preames)

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This is inspired by #77342 (review), and is split off of same with some differences in style.

A select is a vmerge.vv with the additional cost of materializing the bitmask vector in a vreg. All masks fit within a single vector register (e8 + m8 is the worst case), and thus our worst case cost should be roughly 3 (2 scalar to produce the address, one vector load op). Given most shuffles are small, and the mask will be instead produced by LUI/ADDI + vmv.s.x or ADDI + vmv.s.x, using 2 as the default seems quite reasonable. At worst, we're not going to be off by much.

The prior lowering scaled the cost of the bitmask with LMUL, which I don't understand. At m1 it did use the same base cost of 2. (@lukel97 You wrote the original code here, anything I'm missing here?)

Patch is 54.92 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/77963.diff

3 Files Affected:

  • (modified) llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp (+6-5)
  • (modified) llvm/test/Analysis/CostModel/RISCV/shuffle-insert_subvector.ll (+38-38)
  • (modified) llvm/test/Analysis/CostModel/RISCV/shuffle-select.ll (+4-4)
diff --git a/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp b/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
index b3916c98700519..94c895a58a9515 100644
--- a/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
+++ b/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
@@ -84,8 +84,6 @@ RISCVTTIImpl::getRISCVInstructionCost(ArrayRef<unsigned> OpCodes, MVT VT,
       Cost += VL;
       break;
     }
-    case RISCV::VMV_S_X:
-      // FIXME: VMV_S_X doesn't use LMUL, the cost should be 1
     default:
       Cost += LMULCost;
     }
@@ -443,10 +441,13 @@ InstructionCost RISCVTTIImpl::getShuffleCost(TTI::ShuffleKind Kind,
     // vsetivli     zero, 8, e8, mf2, ta, ma (ignored)
     // vmv.s.x      v0, a0
     // vmerge.vvm   v8, v9, v8, v0
+    // We use 2 for the cost of the mask materialization as this is the true
+    // cost for small masks and most shuffles are small.  At worst, this cost
+    // should be a very small constant for the constant pool load.  As such,
+    // we may bias towards large selects slightly more than truely warranted.
     return LT.first *
-           (TLI->getLMULCost(LT.second) + // FIXME: should be 1 for li
-            getRISCVInstructionCost({RISCV::VMV_S_X, RISCV::VMERGE_VVM},
-                                    LT.second, CostKind));
+           (2 + getRISCVInstructionCost({RISCV::VMERGE_VVM},
+                                        LT.second, CostKind));
   }
   case TTI::SK_Broadcast: {
     bool HasScalar = (Args.size() > 0) && (Operator::getOpcode(Args[0]) ==
diff --git a/llvm/test/Analysis/CostModel/RISCV/shuffle-insert_subvector.ll b/llvm/test/Analysis/CostModel/RISCV/shuffle-insert_subvector.ll
index af656b4d7976d2..9a333dc8b8ddda 100644
--- a/llvm/test/Analysis/CostModel/RISCV/shuffle-insert_subvector.ll
+++ b/llvm/test/Analysis/CostModel/RISCV/shuffle-insert_subvector.ll
@@ -9,13 +9,13 @@ define void @test_vXf64(<2 x double> %src128, <4 x double> %src256, <8 x double>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: %src128_256 = shufflevector <2 x double> %src128, <2 x double> undef, <4 x i32> <i32 0, i32 1, i32 poison, i32 poison>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: %src128_512 = shufflevector <2 x double> %src128, <2 x double> undef, <8 x i32> <i32 0, i32 1, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: %src256_512 = shufflevector <4 x double> %src256, <4 x double> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 poison, i32 poison, i32 poison, i32 poison>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %V256_01 = shufflevector <4 x double> %src256, <4 x double> %src128_256, <4 x i32> <i32 4, i32 5, i32 2, i32 3>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V256_01 = shufflevector <4 x double> %src256, <4 x double> %src128_256, <4 x i32> <i32 4, i32 5, i32 2, i32 3>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %V256_23 = shufflevector <4 x double> %src256, <4 x double> %src128_256, <4 x i32> <i32 0, i32 1, i32 4, i32 5>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 12 for instruction: %V512_01 = shufflevector <8 x double> %src512, <8 x double> %src128_512, <8 x i32> <i32 8, i32 9, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %V512_01 = shufflevector <8 x double> %src512, <8 x double> %src128_512, <8 x i32> <i32 8, i32 9, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V512_23 = shufflevector <8 x double> %src512, <8 x double> %src128_512, <8 x i32> <i32 0, i32 1, i32 8, i32 9, i32 4, i32 5, i32 6, i32 7>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V512_45 = shufflevector <8 x double> %src512, <8 x double> %src128_512, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 8, i32 9, i32 6, i32 7>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V512_67 = shufflevector <8 x double> %src512, <8 x double> %src128_512, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 8, i32 9>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 12 for instruction: %V512_0123 = shufflevector <8 x double> %src512, <8 x double> %src256_512, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 4, i32 5, i32 6, i32 7>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %V512_0123 = shufflevector <8 x double> %src512, <8 x double> %src256_512, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 4, i32 5, i32 6, i32 7>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V512_4567 = shufflevector <8 x double> %src512, <8 x double> %src256_512, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 8, i32 9, i32 10, i32 11>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: ret void
 ;
@@ -23,13 +23,13 @@ define void @test_vXf64(<2 x double> %src128, <4 x double> %src256, <8 x double>
 ; SIZE-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: %src128_256 = shufflevector <2 x double> %src128, <2 x double> undef, <4 x i32> <i32 0, i32 1, i32 poison, i32 poison>
 ; SIZE-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: %src128_512 = shufflevector <2 x double> %src128, <2 x double> undef, <8 x i32> <i32 0, i32 1, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison>
 ; SIZE-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: %src256_512 = shufflevector <4 x double> %src256, <4 x double> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 poison, i32 poison, i32 poison, i32 poison>
-; SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V256_01 = shufflevector <4 x double> %src256, <4 x double> %src128_256, <4 x i32> <i32 4, i32 5, i32 2, i32 3>
+; SIZE-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %V256_01 = shufflevector <4 x double> %src256, <4 x double> %src128_256, <4 x i32> <i32 4, i32 5, i32 2, i32 3>
 ; SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %V256_23 = shufflevector <4 x double> %src256, <4 x double> %src128_256, <4 x i32> <i32 0, i32 1, i32 4, i32 5>
-; SIZE-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %V512_01 = shufflevector <8 x double> %src512, <8 x double> %src128_512, <8 x i32> <i32 8, i32 9, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+; SIZE-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %V512_01 = shufflevector <8 x double> %src512, <8 x double> %src128_512, <8 x i32> <i32 8, i32 9, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
 ; SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %V512_23 = shufflevector <8 x double> %src512, <8 x double> %src128_512, <8 x i32> <i32 0, i32 1, i32 8, i32 9, i32 4, i32 5, i32 6, i32 7>
 ; SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %V512_45 = shufflevector <8 x double> %src512, <8 x double> %src128_512, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 8, i32 9, i32 6, i32 7>
 ; SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %V512_67 = shufflevector <8 x double> %src512, <8 x double> %src128_512, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 8, i32 9>
-; SIZE-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %V512_0123 = shufflevector <8 x double> %src512, <8 x double> %src256_512, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 4, i32 5, i32 6, i32 7>
+; SIZE-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %V512_0123 = shufflevector <8 x double> %src512, <8 x double> %src256_512, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 4, i32 5, i32 6, i32 7>
 ; SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %V512_4567 = shufflevector <8 x double> %src512, <8 x double> %src256_512, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 8, i32 9, i32 10, i32 11>
 ; SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: ret void
 ;
@@ -53,13 +53,13 @@ define void @test_vXi64(<2 x i64> %src128, <4 x i64> %src256, <8 x i64> %src512)
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: %src128_256 = shufflevector <2 x i64> %src128, <2 x i64> undef, <4 x i32> <i32 0, i32 1, i32 poison, i32 poison>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: %src128_512 = shufflevector <2 x i64> %src128, <2 x i64> undef, <8 x i32> <i32 0, i32 1, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: %src256_512 = shufflevector <4 x i64> %src256, <4 x i64> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 poison, i32 poison, i32 poison, i32 poison>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %V256_01 = shufflevector <4 x i64> %src256, <4 x i64> %src128_256, <4 x i32> <i32 4, i32 5, i32 2, i32 3>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V256_01 = shufflevector <4 x i64> %src256, <4 x i64> %src128_256, <4 x i32> <i32 4, i32 5, i32 2, i32 3>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %V256_23 = shufflevector <4 x i64> %src256, <4 x i64> %src128_256, <4 x i32> <i32 0, i32 1, i32 4, i32 5>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 12 for instruction: %V512_01 = shufflevector <8 x i64> %src512, <8 x i64> %src128_512, <8 x i32> <i32 8, i32 9, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %V512_01 = shufflevector <8 x i64> %src512, <8 x i64> %src128_512, <8 x i32> <i32 8, i32 9, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V512_23 = shufflevector <8 x i64> %src512, <8 x i64> %src128_512, <8 x i32> <i32 0, i32 1, i32 8, i32 9, i32 4, i32 5, i32 6, i32 7>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V512_45 = shufflevector <8 x i64> %src512, <8 x i64> %src128_512, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 8, i32 9, i32 6, i32 7>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V512_67 = shufflevector <8 x i64> %src512, <8 x i64> %src128_512, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 8, i32 9>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 12 for instruction: %V512_0123 = shufflevector <8 x i64> %src512, <8 x i64> %src256_512, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 4, i32 5, i32 6, i32 7>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %V512_0123 = shufflevector <8 x i64> %src512, <8 x i64> %src256_512, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 4, i32 5, i32 6, i32 7>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V512_4567 = shufflevector <8 x i64> %src512, <8 x i64> %src256_512, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 8, i32 9, i32 10, i32 11>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: ret void
 ;
@@ -67,13 +67,13 @@ define void @test_vXi64(<2 x i64> %src128, <4 x i64> %src256, <8 x i64> %src512)
 ; SIZE-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: %src128_256 = shufflevector <2 x i64> %src128, <2 x i64> undef, <4 x i32> <i32 0, i32 1, i32 poison, i32 poison>
 ; SIZE-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: %src128_512 = shufflevector <2 x i64> %src128, <2 x i64> undef, <8 x i32> <i32 0, i32 1, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison>
 ; SIZE-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: %src256_512 = shufflevector <4 x i64> %src256, <4 x i64> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 poison, i32 poison, i32 poison, i32 poison>
-; SIZE-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V256_01 = shufflevector <4 x i64> %src256, <4 x i64> %src128_256, <4 x i32> <i32 4, i32 5, i32 2, i32 3>
+; SIZE-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %V256_01 = shufflevector <4 x i64> %src256, <4 x i64> %src128_256, <4 x i32> <i32 4, i32 5, i32 2, i32 3>
 ; SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %V256_23 = shufflevector <4 x i64> %src256, <4 x i64> %src128_256, <4 x i32> <i32 0, i32 1, i32 4, i32 5>
-; SIZE-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %V512_01 = shufflevector <8 x i64> %src512, <8 x i64> %src128_512, <8 x i32> <i32 8, i32 9, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+; SIZE-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %V512_01 = shufflevector <8 x i64> %src512, <8 x i64> %src128_512, <8 x i32> <i32 8, i32 9, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
 ; SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %V512_23 = shufflevector <8 x i64> %src512, <8 x i64> %src128_512, <8 x i32> <i32 0, i32 1, i32 8, i32 9, i32 4, i32 5, i32 6, i32 7>
 ; SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %V512_45 = shufflevector <8 x i64> %src512, <8 x i64> %src128_512, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 8, i32 9, i32 6, i32 7>
 ; SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %V512_67 = shufflevector <8 x i64> %src512, <8 x i64> %src128_512, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 8, i32 9>
-; SIZE-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %V512_0123 = shufflevector <8 x i64> %src512, <8 x i64> %src256_512, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 4, i32 5, i32 6, i32 7>
+; SIZE-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %V512_0123 = shufflevector <8 x i64> %src512, <8 x i64> %src256_512, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 4, i32 5, i32 6, i32 7>
 ; SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %V512_4567 = shufflevector <8 x i64> %src512, <8 x i64> %src256_512, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 8, i32 9, i32 10, i32 11>
 ; SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: ret void
 ;
@@ -102,13 +102,13 @@ define void @test_vXf32(<2 x float> %src64, <4 x float> %src128, <8 x float> %sr
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 0 for instruction: %src256_512 = shufflevector <8 x float> %src256, <8 x float> undef, <16 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %V128_01 = shufflevector <4 x float> %src128, <4 x float> %src64_128, <4 x i32> <i32 4, i32 5, i32 2, i32 3>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %V128_23 = shufflevector <4 x float> %src128, <4 x float> %src64_128, <4 x i32> <i32 0, i32 1, i32 4, i32 5>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %V256_01 = shufflevector <8 x float> %src256, <8 x float> %src64_256, <8 x i32> <i32 8, i32 9, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V256_01 = shufflevector <8 x float> %src256, <8 x float> %src64_256, <8 x i32> <i32 8, i32 9, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %V256_23 = shufflevector <8 x float> %src256, <8 x float> %src64_256, <8 x i32> <i32 0, i32 1, i32 8, i32 9, i32 4, i32 5, i32 6, i32 7>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %V256_45 = shufflevector <8 x float> %src256, <8 x float> %src64_256, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 8, i32 9, i32 6, i32 7>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %V256_67 = shufflevector <8 x float> %src256, <8 x float> %src64_256, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 8, i32 9>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %V256_0123 = shufflevector <8 x float> %src256, <8 x float> %src128_256, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 4, i32 5, i32 6, i32 7>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V256_0123 = shufflevector <8 x float> %src256, <8 x float> %src128_256, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 4, i32 5, i32 6, i32 7>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %V256_4567 = shufflevector <8 x float> %src256, <8 x float> %src128_256, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 8, i32 9, i32 10, i32 11>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 12 for instruction: %V512_01 = shufflevector <16 x float> %src512, <16 x float> %src64_512, <16 x i32> <i32 16, i32 17, 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>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %V512_01 = shufflevector <16 x float> %src512, <16 x float> %src64_512, <16 x i32> <i32 16, i32 17, 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>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V512_23 = shufflevector <16 x float> %src512, <16 x float> %src64_512, <16 x i32> <i32 0, i32 1, i32 16, i32 17, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V512_45 = shufflevector <16 x float> %src512, <16 x float> %src64_512, <16 x i32> <i32 0, i32 1, i32 2, i32 3, i32 16, i32 17, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V512_67 = shufflevector <16 x float> %src512, <16 x float> %src64_512, <16 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 16, i32 17, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
@@ -116,11 +116,11 @@ define void @test_vXf32(<2 x float> %src64, <4 x float> %src128, <8 x float> %sr
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V512_AB = shufflevector <16 x float> %src512, <16 x float> %src64_512, <16 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 16, i32 17, i32 12, i32 13, i32 14, i32 15>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V512_CD = shufflevector <16 x float> %src512, <16 x float> %src64_512, <16 x i32> <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 16, i32 17, i32 14, i32 15>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V512_EF = shufflevector <16 x float> %src512, <16 x float> %src64_512, <16 x i32> <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 16, i32 17>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 12 for instruction: %V512_0123 = shufflevector <16 x float> %src512, <16 x float> %src128_512, <16 x i32> <i32 16, i32 17, i32 18, i32 19, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %V512_0123 = shufflevector <16 x float> %src512, <16 x float> %src128_512, <16 x i32> <i32 16, i32 17, i32 18, i32 19, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V512_4567 = shufflevector <16 x float> %src512, <16 x float> %src128_512, <16 x i32> <i32 0, i32 1, i32 2, i32 3, i32 16, i32 17, i32 18, i32 19, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V512_89AB = shufflevector <16 x float> %src512, <16 x float> %src128_512, <16 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 16, i32 17, i32 18, i32 19, i32 12, i32 13, i32 14, i32 15>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %V512_CDEF = shufflevector <16 x float> %src512, <16 x float> %src128_512, <16 x i32> <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 16, i32 17, i32 18, i32 19>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 12 for instruction: ...
[truncated]

@preames preames mentioned this pull request Jan 12, 2024
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⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command: 
git-clang-format --diff 5ce067d592b78fd3142364e06bae4da2a3a1e944 e886bb3556d4058dede441a8f3e80c39249e6f82 -- llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
View the diff from clang-format here. 
diff --git a/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp b/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
index 94c895a58a..41cc081a67 100644
--- a/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
+++ b/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
@@ -445,9 +445,8 @@ InstructionCost RISCVTTIImpl::getShuffleCost(TTI::ShuffleKind Kind,
     // cost for small masks and most shuffles are small.  At worst, this cost
     // should be a very small constant for the constant pool load.  As such,
     // we may bias towards large selects slightly more than truely warranted.
-    return LT.first *
-           (2 + getRISCVInstructionCost({RISCV::VMERGE_VVM},
-                                        LT.second, CostKind));
+    return LT.first * (2 + getRISCVInstructionCost({RISCV::VMERGE_VVM},
+                                                   LT.second, CostKind));
   }
   case TTI::SK_Broadcast: {
     bool HasScalar = (Args.size() > 0) && (Operator::getOpcode(Args[0]) ==

arcbbb
arcbbb reviewed Jan 13, 2024
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llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
(TLI->getLMULCost(LT.second) + // FIXME: should be 1 for li
getRISCVInstructionCost({RISCV::VMV_S_X, RISCV::VMERGE_VVM},
LT.second, CostKind));
(2 + getRISCVInstructionCost({RISCV::VMERGE_VVM},
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@arcbbb arcbbb Jan 13, 2024 •
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Can we query the cost of VMV_S_*/VMV_*_S instead? So vendors can provide their own number in getRISCVInstructionCost.

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That makes sense. We would also need to address this FIXME in getRISCVInstructionCost too:

llvm-project/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp

Lines 87 to 90 in e040252

case RISCV::VMV_S_X:
// FIXME: VMV_S_X doesn't use LMUL, the cost should be 1
default:
Cost += LMULCost;

Probably needs to be done in a separate patch.

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Can we query the cost of VMV_S_/VMV__S instead? So vendors can provide their own number in getRISCVInstructionCost.

I would actively prefer not to add complexity unless needed. To you have knowledge of a particular processor which would need this override?

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@lukel97 Agree. Is is not blocking issue.
@preames I would like to override VMV_X_S for sifive-x280, and VMV_S_X is for consistency.

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lukel97 commented Jan 15, 2024

The prior lowering scaled the cost of the bitmask with LMUL, which I don't understand. At m1 it did use the same base cost of 2. (@lukel97 You wrote the original code here, anything I'm missing here?)

Nope, looks like an oversight. AFAIK the vmerge.vvm is the only op that should be scaled by LMUL

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preames commented Jan 18, 2024

ping

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arcbbb approved these changes Jan 18, 2024
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LGTM as change on VMV_S_* can be a separate PR.

@preames preames merged commit 2663d2c into llvm:main Jan 18, 2024
@preames preames deleted the pr-riscv-tti-select-cost branch January 18, 2024 18:24
arcbbb added a commit to arcbbb/llvm-project that referenced this pull request Jan 19, 2024
@arcbbb
[RISCV][CostModel] Make VMV_S_* and VMV_*_S cost independent of LMUL
d720e0a 
Following llvm#77963, instructions like VMV_S_X/VMV_X_S/VFMV_S_F/VFMV_F_S
handle single element, so the cost don't scale with LMUL.
@arcbbb arcbbb mentioned this pull request Jan 19, 2024
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arcbbb added a commit that referenced this pull request Jan 23, 2024
@arcbbb
[RISCV][CostModel] Make VMV_S_X and VMV_X_S cost independent of LMUL (#…
7e63940 
…78739)

Following #77963, instructions like VMV_S_X/VMV_X_S 
handle single element, so the cost don't scale with LMUL.
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@arcbbb arcbbb arcbbb approved these changes

@lukel97 lukel97 Awaiting requested review from lukel97

@topperc topperc Awaiting requested review from topperc

@wangpc-pp wangpc-pp Awaiting requested review from wangpc-pp

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