[llvm] ca0cd67 - [RISCV] Improve SK_Reverse shuffle costs for fixed length vectors

Philip Reames via llvm-commits llvm-commits at lists.llvm.org
Mon Mar 13 15:17:52 PDT 2023


Author: Philip Reames
Date: 2023-03-13T15:17:42-07:00
New Revision: ca0cd670dcf13c152db0a69ef14037ff19be9b29

URL: https://github.com/llvm/llvm-project/commit/ca0cd670dcf13c152db0a69ef14037ff19be9b29
DIFF: https://github.com/llvm/llvm-project/commit/ca0cd670dcf13c152db0a69ef14037ff19be9b29.diff

LOG: [RISCV] Improve SK_Reverse shuffle costs for fixed length vectors

As noted by @luke (https://reviews.llvm.org/D145953#inline-1409312), we were accounting for the cost of vector element size using vlenb whereas the expression can be constant folded for fixed length vectors.

Differential Revision: https://reviews.llvm.org/D145973

Added: 
    

Modified: 
    llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
    llvm/test/Analysis/CostModel/RISCV/shuffle-reverse.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp b/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
index 35a3621ab96a..1e78ef6e8f7a 100644
--- a/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
+++ b/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
@@ -333,7 +333,12 @@ InstructionCost RISCVTTIImpl::getShuffleCost(TTI::ShuffleKind Kind,
     // TODO: Multiplying by LT.first implies this legalizes into multiple copies
     // of similar code, but I think we expand through memory.
     return 2 * LT.first * getLMULCost(LT.second);
-  case TTI::SK_Reverse:
+  case TTI::SK_Reverse: {
+    // TODO: Cases to improve here:
+    // * LMUL > 1
+    // * i64 on RV32
+    // * i1 vector
+
     // Most of the cost here is producing the vrgather index register
     // Example sequence:
     //   csrr a0, vlenb
@@ -343,10 +348,15 @@ InstructionCost RISCVTTIImpl::getShuffleCost(TTI::ShuffleKind Kind,
     //   vid.v v9
     //   vrsub.vx v10, v9, a0
     //   vrgather.vv v9, v8, v10
+    unsigned LenCost = 3;
+    if (LT.second.isFixedLengthVector())
+      // vrsub.vi has a 5 bit immediate field, otherwise an li suffices
+      LenCost = isInt<5>(LT.second.getVectorNumElements() - 1) ? 0 : 1;
     if (Tp->getElementType()->isIntegerTy(1))
       // Mask operation additionally required extend and truncate
-      return LT.first * 9;
-    return LT.first * 6;
+      return LT.first * (LenCost + 6);
+    return LT.first * (LenCost + 3);
+  }
   }
   return BaseT::getShuffleCost(Kind, Tp, Mask, CostKind, Index, SubTp);
 }

diff  --git a/llvm/test/Analysis/CostModel/RISCV/shuffle-reverse.ll b/llvm/test/Analysis/CostModel/RISCV/shuffle-reverse.ll
index 18e614cf236e..ae9d34dc8435 100644
--- a/llvm/test/Analysis/CostModel/RISCV/shuffle-reverse.ll
+++ b/llvm/test/Analysis/CostModel/RISCV/shuffle-reverse.ll
@@ -8,28 +8,28 @@
 define void @reverse() {
 ;
 ; CHECK-LABEL: 'reverse'
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %v2i8 = shufflevector <2 x i8> undef, <2 x i8> undef, <2 x i32> <i32 1, i32 0>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %v4i8 = shufflevector <4 x i8> undef, <4 x i8> undef, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %v8i8 = shufflevector <8 x i8> undef, <8 x i8> undef, <8 x i32> <i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 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 8, i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %v2i16 = shufflevector <2 x i16> undef, <2 x i16> undef, <2 x i32> <i32 1, i32 0>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %v4i16 = shufflevector <4 x i16> undef, <4 x i16> undef, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %v8i16 = shufflevector <8 x i16> undef, <8 x i16> undef, <8 x i32> <i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
-; CHECK-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 12, i32 11, i32 10, i32 9, i32 8, i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %v2i32 = shufflevector <2 x i32> undef, <2 x i32> undef, <2 x i32> <i32 1, i32 0>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %v4i32 = shufflevector <4 x i32> undef, <4 x i32> undef, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
-; CHECK-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 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %v2i64 = shufflevector <2 x i64> undef, <2 x i64> undef, <2 x i32> <i32 1, i32 0>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %v4i64 = shufflevector <4 x i64> undef, <4 x i64> undef, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %v2f16 = shufflevector <2 x half> undef, <2 x half> undef, <2 x i32> <i32 1, i32 0>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %v4f16 = shufflevector <4 x half> undef, <4 x half> undef, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %v8f16 = shufflevector <8 x half> undef, <8 x half> undef, <8 x i32> <i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %v16f16 = shufflevector <16 x half> undef, <16 x half> undef, <16 x i32> <i32 15, i32 14, i32 13, i32 12, i32 11, i32 10, i32 9, i32 8, i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %v2f32 = shufflevector <2 x float> undef, <2 x float> undef, <2 x i32> <i32 1, i32 0>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %v4f32 = shufflevector <4 x float> undef, <4 x float> undef, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %v8f32 = shufflevector <8 x float> undef, <8 x float> undef, <8 x i32> <i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %v2f64 = shufflevector <2 x double> undef, <2 x double> undef, <2 x i32> <i32 1, i32 0>
-; CHECK-NEXT:  Cost Model: Found an estimated cost of 6 for instruction: %v4f64 = shufflevector <4 x double> undef, <4 x double> undef, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %v2i8 = shufflevector <2 x i8> undef, <2 x i8> undef, <2 x i32> <i32 1, i32 0>
+; CHECK-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 3, i32 2, i32 1, i32 0>
+; CHECK-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 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
+; CHECK-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 8, i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %v2i16 = shufflevector <2 x i16> undef, <2 x i16> undef, <2 x i32> <i32 1, i32 0>
+; CHECK-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 1, i32 0>
+; CHECK-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 4, i32 3, i32 2, i32 1, i32 0>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %v16i16 = shufflevector <16 x i16> undef, <16 x i16> undef, <16 x i32> <i32 15, i32 14, i32 13, i32 12, i32 11, i32 10, i32 9, i32 8, i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %v2i32 = shufflevector <2 x i32> undef, <2 x i32> undef, <2 x i32> <i32 1, i32 0>
+; CHECK-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 1, i32 0>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %v8i32 = shufflevector <8 x i32> undef, <8 x i32> undef, <8 x i32> <i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %v2i64 = shufflevector <2 x i64> undef, <2 x i64> undef, <2 x i32> <i32 1, i32 0>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %v4i64 = shufflevector <4 x i64> undef, <4 x i64> undef, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %v2f16 = shufflevector <2 x half> undef, <2 x half> undef, <2 x i32> <i32 1, i32 0>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %v4f16 = shufflevector <4 x half> undef, <4 x half> undef, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %v8f16 = shufflevector <8 x half> undef, <8 x half> undef, <8 x i32> <i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %v16f16 = shufflevector <16 x half> undef, <16 x half> undef, <16 x i32> <i32 15, i32 14, i32 13, i32 12, i32 11, i32 10, i32 9, i32 8, i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %v2f32 = shufflevector <2 x float> undef, <2 x float> undef, <2 x i32> <i32 1, i32 0>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %v4f32 = shufflevector <4 x float> undef, <4 x float> undef, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %v8f32 = shufflevector <8 x float> undef, <8 x float> undef, <8 x i32> <i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %v2f64 = shufflevector <2 x double> undef, <2 x double> undef, <2 x i32> <i32 1, i32 0>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %v4f64 = shufflevector <4 x double> undef, <4 x double> undef, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
 ; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: ret void
 ;
   %v2i8 = shufflevector <2 x i8> undef, <2 x i8> undef, <2 x i32> <i32 1, i32 0>


        


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