[llvm] c9f9c79 - [NFC][DAGCombine] Change the value of NegatibleCost to make it align with the semantics

[QingShan Zhang via llvm-commits]

Author: QingShan Zhang
Date: 2020-04-15T02:20:58Z
New Revision: c9f9c79c5a4868f8bb7526c104aa18fd1dc42002

URL: https://github.com/llvm/llvm-project/commit/c9f9c79c5a4868f8bb7526c104aa18fd1dc42002
DIFF: https://github.com/llvm/llvm-project/commit/c9f9c79c5a4868f8bb7526c104aa18fd1dc42002.diff

LOG: [NFC][DAGCombine] Change the value of NegatibleCost to make it align with the semantics

This is a minor NFC change to make the code more clear. We have the NegatibleCost that
has cheaper, neutral, and expensive. Typically, the smaller one means the less cost.
It is inverse for current implementation, which makes following code not easy to read.
If (CostX > CostY) negate(X)

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D77993

Added: 
    

Modified: 
    llvm/include/llvm/CodeGen/TargetLowering.h
    llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp

Removed: 
    


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diff  --git a/llvm/include/llvm/CodeGen/TargetLowering.h b/llvm/include/llvm/CodeGen/TargetLowering.h
index 4b0592d782ae..98df5214d815 100644
--- a/llvm/include/llvm/CodeGen/TargetLowering.h
+++ b/llvm/include/llvm/CodeGen/TargetLowering.h
@@ -257,9 +257,9 @@ class TargetLoweringBase {
 
   /// Enum that specifies when a float negation is beneficial.
   enum class NegatibleCost {
-    Expensive = 0,  // Negated expression is more expensive.
+    Cheaper = 0,    // Negated expression is cheaper.
     Neutral = 1,    // Negated expression has the same cost.
-    Cheaper = 2     // Negated expression is cheaper.
+    Expensive = 2   // Negated expression is more expensive.
   };
 
   class ArgListEntry {

diff  --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 6c3e952f7661..5110dd512434 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -5671,10 +5671,10 @@ TargetLowering::getNegatibleCost(SDValue Op, SelectionDAG &DAG,
                                         ForCodeSize, Depth + 1);
     NegatibleCost V1 = getNegatibleCost(Op.getOperand(1), DAG, LegalOperations,
                                         ForCodeSize, Depth + 1);
-    NegatibleCost V01 = std::max(V0, V1);
+    NegatibleCost V01 = std::min(V0, V1);
     if (V01 == NegatibleCost::Expensive)
       return NegatibleCost::Expensive;
-    return std::max(V01, V2);
+    return std::min(V01, V2);
   }
 
   case ISD::FP_EXTEND:
@@ -5776,7 +5776,7 @@ SDValue TargetLowering::getNegatedExpression(SDValue Op, SelectionDAG &DAG,
     SDValue NegZ = getNegatedExpression(Z, DAG, LegalOps, OptForSize, Depth);
     NegatibleCost CostX = getNegatibleCost(X, DAG, LegalOps, OptForSize, Depth);
     NegatibleCost CostY = getNegatibleCost(Y, DAG, LegalOps, OptForSize, Depth);
-    if (CostX > CostY) {
+    if (CostX <= CostY) {
       // fold (fneg (fma X, Y, Z)) -> (fma (fneg X), Y, (fneg Z))
       SDValue NegX = getNegatedExpression(X, DAG, LegalOps, OptForSize, Depth);
       return DAG.getNode(Opcode, DL, VT, NegX, Y, NegZ, Flags);