[AArch64] Give a higher cost for more expensive SVE FCMP instructions

Author: davemgreen

llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp

@@ -4409,6 +4409,32 @@ AArch64TTIImpl::getAddressComputationCost(Type *PtrTy, ScalarEvolution *SE,
   return 1;
 }
 
+/// Check whether Opcode1 has less throughput according to the scheduling
+/// model than Opcode2.
+bool AArch64TTIImpl::hasKnownLowerThroughputFromSchedulingModel(
+    unsigned Opcode1, unsigned Opcode2) const {
+  const MCSchedModel &Sched = ST->getSchedModel();
+  const TargetInstrInfo *TII = ST->getInstrInfo();
+  if (!Sched.hasInstrSchedModel())
+    return false;
+
+  const MCSchedClassDesc *SCD1 =
+      Sched.getSchedClassDesc(TII->get(Opcode1).getSchedClass());
+  const MCSchedClassDesc *SCD2 =
+      Sched.getSchedClassDesc(TII->get(Opcode2).getSchedClass());
+  // We cannot handle variant scheduling classes without an MI. If we need to
+  // support them for any of the instructions we query the information of we
+  // might need to add a way to resolve them without a MI or not use the
+  // scheduling info.
+  assert(!SCD1->isVariant() && !SCD2->isVariant() &&
+         "Cannot handle variant scheduling classes without an MI");
+  if (!SCD1->isValid() || !SCD2->isValid())
+    return false;
+
+  return MCSchedModel::getReciprocalThroughput(*ST, *SCD1) >
+         MCSchedModel::getReciprocalThroughput(*ST, *SCD2);
+}
+
 InstructionCost AArch64TTIImpl::getCmpSelInstrCost(
     unsigned Opcode, Type *ValTy, Type *CondTy, CmpInst::Predicate VecPred,
     TTI::TargetCostKind CostKind, TTI::OperandValueInfo Op1Info,
@@ -4506,6 +4532,12 @@ InstructionCost AArch64TTIImpl::getCmpSelInstrCost(
              (VecPred == FCmpInst::FCMP_ONE || VecPred == FCmpInst::FCMP_UEQ))
       Factor = 3; // fcmxx+fcmyy+or
 
+    if (isa<ScalableVectorType>(ValTy) &&
+        CostKind == TTI::TCK_RecipThroughput &&
+        hasKnownLowerThroughputFromSchedulingModel(AArch64::FCMEQ_PPzZZ_S,
+                                                   AArch64::FCMEQv4f32))
+      Factor *= 2;
+
     return Factor * (CostKind == TTI::TCK_Latency ? 2 : LT.first);
   }
 

llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h

@@ -174,6 +174,11 @@ class AArch64TTIImpl final : public BasicTTIImplBase<AArch64TTIImpl> {
 
   bool prefersVectorizedAddressing() const override;
 
+  /// Check whether Opcode1 has less throughput according to the scheduling
+  /// model than Opcode2.
+  bool hasKnownLowerThroughputFromSchedulingModel(unsigned Opcode1,
+                                                  unsigned Opcode2) const;
+
   InstructionCost
   getMaskedMemoryOpCost(unsigned Opcode, Type *Src, Align Alignment,
                         unsigned AddressSpace,

llvm/test/Analysis/CostModel/AArch64/sve-cmpsel.ll

@@ -58,10 +58,10 @@ define <vscale x 32 x i1> @cmp_nxv32i1() {
 ; Check fcmp for legal FP vectors
 define void @cmp_legal_fp() #0 {
 ; CHECK-LABEL: 'cmp_legal_fp'
-; CHECK-NEXT:  Cost Model: Found costs of RThru:1 CodeSize:1 Lat:2 SizeLat:1 for: %1 = fcmp oge <vscale x 2 x double> undef, undef
-; CHECK-NEXT:  Cost Model: Found costs of RThru:1 CodeSize:1 Lat:2 SizeLat:1 for: %2 = fcmp oge <vscale x 4 x float> undef, undef
-; CHECK-NEXT:  Cost Model: Found costs of RThru:1 CodeSize:1 Lat:2 SizeLat:1 for: %3 = fcmp oge <vscale x 8 x half> undef, undef
-; CHECK-NEXT:  Cost Model: Found costs of RThru:11 CodeSize:5 Lat:5 SizeLat:5 for: %4 = fcmp oge <vscale x 8 x bfloat> undef, undef
+; CHECK-NEXT:  Cost Model: Found costs of RThru:2 CodeSize:1 Lat:2 SizeLat:1 for: %1 = fcmp oge <vscale x 2 x double> undef, undef
+; CHECK-NEXT:  Cost Model: Found costs of RThru:2 CodeSize:1 Lat:2 SizeLat:1 for: %2 = fcmp oge <vscale x 4 x float> undef, undef
+; CHECK-NEXT:  Cost Model: Found costs of RThru:2 CodeSize:1 Lat:2 SizeLat:1 for: %3 = fcmp oge <vscale x 8 x half> undef, undef
+; CHECK-NEXT:  Cost Model: Found costs of RThru:13 CodeSize:5 Lat:5 SizeLat:5 for: %4 = fcmp oge <vscale x 8 x bfloat> undef, undef
 ; CHECK-NEXT:  Cost Model: Found costs of RThru:0 CodeSize:1 Lat:1 SizeLat:1 for: ret void
 ;
   %1 = fcmp oge <vscale x 2 x double> undef, undef
@@ -74,7 +74,7 @@ define void @cmp_legal_fp() #0 {
 ; Check fcmp for an illegal FP vector
 define <vscale x 16 x i1> @cmp_nxv16f16() {
 ; CHECK-LABEL: 'cmp_nxv16f16'
-; CHECK-NEXT:  Cost Model: Found costs of 2 for: %res = fcmp oge <vscale x 16 x half> undef, undef
+; CHECK-NEXT:  Cost Model: Found costs of RThru:4 CodeSize:2 Lat:2 SizeLat:2 for: %res = fcmp oge <vscale x 16 x half> undef, undef
 ; CHECK-NEXT:  Cost Model: Found costs of RThru:0 CodeSize:1 Lat:1 SizeLat:1 for: ret <vscale x 16 x i1> %res
 ;
   %res = fcmp oge <vscale x 16 x half> undef, undef