[llvm] 0af4147 - [ARM][CostModel] CodeSize costs for i1 arith ops

[Sam Parker via llvm-commits]

Author: Sam Parker
Date: 2020-09-07T09:27:18+01:00
New Revision: 0af4147804aa0aa906a2ac913fe5639639afb9bb

URL: https://github.com/llvm/llvm-project/commit/0af4147804aa0aa906a2ac913fe5639639afb9bb
DIFF: https://github.com/llvm/llvm-project/commit/0af4147804aa0aa906a2ac913fe5639639afb9bb.diff

LOG: [ARM][CostModel] CodeSize costs for i1 arith ops

When optimising for size, make the cost of i1 logical operations
relatively expensive so that optimisations don't try to combine
predicates.

Differential Revision: https://reviews.llvm.org/D86525

Added: 
    

Modified: 
    llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
    llvm/test/Analysis/CostModel/ARM/arith.ll

Removed: 
    


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diff  --git a/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp b/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
index f3206306a3b6..c789b35f32af 100644
--- a/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
+++ b/llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
@@ -1039,13 +1039,28 @@ int ARMTTIImpl::getArithmeticInstrCost(unsigned Opcode, Type *Ty,
                                        TTI::OperandValueProperties Opd2PropInfo,
                                        ArrayRef<const Value *> Args,
                                        const Instruction *CxtI) {
+  int ISDOpcode = TLI->InstructionOpcodeToISD(Opcode);
+  if (ST->isThumb() && CostKind == TTI::TCK_CodeSize && Ty->isIntegerTy(1)) {
+    // Make operations on i1 relatively expensive as this often involves
+    // combining predicates. AND and XOR should be easier to handle with IT
+    // blocks.
+    switch (ISDOpcode) {
+    default:
+      break;
+    case ISD::AND:
+    case ISD::XOR:
+      return 2;
+    case ISD::OR:
+      return 3;
+    }
+  }
+
   // TODO: Handle more cost kinds.
   if (CostKind != TTI::TCK_RecipThroughput)
     return BaseT::getArithmeticInstrCost(Opcode, Ty, CostKind, Op1Info,
                                          Op2Info, Opd1PropInfo,
                                          Opd2PropInfo, Args, CxtI);
 
-  int ISDOpcode = TLI->InstructionOpcodeToISD(Opcode);
   std::pair<int, MVT> LT = TLI->getTypeLegalizationCost(DL, Ty);
 
   if (ST->hasNEON()) {

diff  --git a/llvm/test/Analysis/CostModel/ARM/arith.ll b/llvm/test/Analysis/CostModel/ARM/arith.ll
index 8513cefe5c11..a1a0d11cac2e 100644
--- a/llvm/test/Analysis/CostModel/ARM/arith.ll
+++ b/llvm/test/Analysis/CostModel/ARM/arith.ll
@@ -63,9 +63,9 @@ define void @i1() {
 ; CHECK-MVE-SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %f = ashr i1 undef, undef
 ; CHECK-MVE-SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %g = lshr i1 undef, undef
 ; CHECK-MVE-SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %h = shl i1 undef, undef
-; CHECK-MVE-SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %i = and i1 undef, undef
-; CHECK-MVE-SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %j = or i1 undef, undef
-; CHECK-MVE-SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %k = xor i1 undef, undef
+; CHECK-MVE-SIZE-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %i = and i1 undef, undef
+; CHECK-MVE-SIZE-NEXT:  Cost Model: Found an estimated cost of 3 for instruction: %j = or i1 undef, undef
+; CHECK-MVE-SIZE-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %k = xor i1 undef, undef
 ; CHECK-MVE-SIZE-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: ret void
 ;
   %c = add i1 undef, undef