Recommit "[ConstraintElimination] Move Value2Index map to ConstraintSystem (NFC)"

This reverts commit 665ee0c.

Fix comments and formatting style.

Author: Zain Jaffal

llvm/include/llvm/Analysis/ConstraintSystem.h

@@ -11,18 +11,25 @@
 
 #include "llvm/ADT/APInt.h"
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/SmallVector.h"
 
 #include <string>
 
 namespace llvm {
 
+class Value;
+
 class ConstraintSystem {
   /// Current linear constraints in the system.
   /// An entry of the form c0, c1, ... cn represents the following constraint:
   ///   c0 >= v0 * c1 + .... + v{n-1} * cn
   SmallVector<SmallVector<int64_t, 8>, 4> Constraints;
 
+  /// A map of variables (IR values) to their corresponding index in the
+  /// constraint system.
+  DenseMap<Value *, unsigned> Value2Index;
+
   /// Current greatest common divisor for all coefficients in the system.
   uint32_t GCD = 1;
 
@@ -52,6 +59,11 @@ class ConstraintSystem {
     return true;
   }
 
+  DenseMap<Value *, unsigned> &getValue2Index() { return Value2Index; }
+  const DenseMap<Value *, unsigned> &getValue2Index() const {
+    return Value2Index;
+  }
+
   bool addVariableRowFill(ArrayRef<int64_t> R) {
     // If all variable coefficients are 0, the constraint does not provide any
     // usable information.

llvm/lib/Transforms/Scalar/ConstraintElimination.cpp

@@ -123,8 +123,6 @@ struct ConstraintTy {
 /// based on signed-ness, certain conditions can be transferred between the two
 /// systems.
 class ConstraintInfo {
-  DenseMap<Value *, unsigned> UnsignedValue2Index;
-  DenseMap<Value *, unsigned> SignedValue2Index;
 
   ConstraintSystem UnsignedCS;
   ConstraintSystem SignedCS;
@@ -135,10 +133,10 @@ class ConstraintInfo {
   ConstraintInfo(const DataLayout &DL) : DL(DL) {}
 
   DenseMap<Value *, unsigned> &getValue2Index(bool Signed) {
-    return Signed ? SignedValue2Index : UnsignedValue2Index;
+    return Signed ? SignedCS.getValue2Index() : UnsignedCS.getValue2Index();
   }
   const DenseMap<Value *, unsigned> &getValue2Index(bool Signed) const {
-    return Signed ? SignedValue2Index : UnsignedValue2Index;
+    return Signed ? SignedCS.getValue2Index() : UnsignedCS.getValue2Index();
   }
 
   ConstraintSystem &getCS(bool Signed) {