[mlir][sparse] fix logical error when generating sort_coo. (llvm#66690)

To fix issue: llvm#66664

Author: PeimingLiu

mlir/lib/Dialect/SparseTensor/Transforms/SparseBufferRewriting.cpp

@@ -563,11 +563,14 @@ static void createChoosePivot(OpBuilder &builder, ModuleOp module,
 //   p = (lo+hi)/2  // pivot index
 //   i = lo
 //   j = hi-1
-//   while (i < j) do {
+//   while (true) do {
 //     while (xs[i] < xs[p]) i ++;
 //     i_eq = (xs[i] == xs[p]);
 //     while (xs[j] > xs[p]) j --;
 //     j_eq = (xs[j] == xs[p]);
+//
+//     if (i >= j) return j + 1;
+//
 //     if (i < j) {
 //       swap(xs[i], xs[j])
 //       if (i == p) {
@@ -581,8 +584,7 @@ static void createChoosePivot(OpBuilder &builder, ModuleOp module,
 //       }
 //     }
 //   }
-//   return p
-//   }
+// }
 static void createPartitionFunc(OpBuilder &builder, ModuleOp module,
                                 func::FuncOp func, uint64_t nx, uint64_t ny,
                                 bool isCoo, uint32_t nTrailingP = 0) {
@@ -605,22 +607,22 @@ static void createPartitionFunc(OpBuilder &builder, ModuleOp module,
   Value i = lo;
   Value j = builder.create<arith::SubIOp>(loc, hi, c1);
   createChoosePivot(builder, module, func, nx, ny, isCoo, i, j, p, args);
-  SmallVector<Value, 3> operands{i, j, p}; // Exactly three values.
-  SmallVector<Type, 3> types{i.getType(), j.getType(), p.getType()};
+  Value trueVal = constantI1(builder, loc, true); // The value for while (true)
+  SmallVector<Value, 4> operands{i, j, p, trueVal}; // Exactly four values.
+  SmallVector<Type, 4> types{i.getType(), j.getType(), p.getType(),
+                             trueVal.getType()};
   scf::WhileOp whileOp = builder.create<scf::WhileOp>(loc, types, operands);
 
   // The before-region of the WhileOp.
-  Block *before =
-      builder.createBlock(&whileOp.getBefore(), {}, types, {loc, loc, loc});
+  Block *before = builder.createBlock(&whileOp.getBefore(), {}, types,
+                                      {loc, loc, loc, loc});
   builder.setInsertionPointToEnd(before);
-  Value cond = builder.create<arith::CmpIOp>(loc, arith::CmpIPredicate::ult,
-                                             before->getArgument(0),
-                                             before->getArgument(1));
-  builder.create<scf::ConditionOp>(loc, cond, before->getArguments());
+  builder.create<scf::ConditionOp>(loc, before->getArgument(3),
+                                   before->getArguments());
 
   // The after-region of the WhileOp.
   Block *after =
-      builder.createBlock(&whileOp.getAfter(), {}, types, {loc, loc, loc});
+      builder.createBlock(&whileOp.getAfter(), {}, types, {loc, loc, loc, loc});
   builder.setInsertionPointToEnd(after);
   i = after->getArgument(0);
   j = after->getArgument(1);
@@ -637,7 +639,8 @@ static void createPartitionFunc(OpBuilder &builder, ModuleOp module,
   j = jresult;
 
   // If i < j:
-  cond = builder.create<arith::CmpIOp>(loc, arith::CmpIPredicate::ult, i, j);
+  Value cond =
+      builder.create<arith::CmpIOp>(loc, arith::CmpIPredicate::ult, i, j);
   scf::IfOp ifOp = builder.create<scf::IfOp>(loc, types, cond, /*else=*/true);
   builder.setInsertionPointToStart(&ifOp.getThenRegion().front());
   SmallVector<Value> swapOperands{i, j};
@@ -675,11 +678,15 @@ static void createPartitionFunc(OpBuilder &builder, ModuleOp module,
   builder.setInsertionPointAfter(ifOp2);
   builder.create<scf::YieldOp>(
       loc,
-      ValueRange{ifOp2.getResult(0), ifOp2.getResult(1), ifOpI.getResult(0)});
+      ValueRange{ifOp2.getResult(0), ifOp2.getResult(1), ifOpI.getResult(0),
+                 /*cont=*/constantI1(builder, loc, true)});
 
-  // False branch for if i < j:
+  // False branch for if i < j (i.e., i >= j):
   builder.setInsertionPointToStart(&ifOp.getElseRegion().front());
-  builder.create<scf::YieldOp>(loc, ValueRange{i, j, p});
+  p = builder.create<arith::AddIOp>(loc, j,
+                                    constantOne(builder, loc, j.getType()));
+  builder.create<scf::YieldOp>(
+      loc, ValueRange{i, j, p, /*cont=*/constantI1(builder, loc, false)});
 
   // Return for the whileOp.
   builder.setInsertionPointAfter(ifOp);
@@ -927,6 +934,8 @@ createQuickSort(OpBuilder &builder, ModuleOp module, func::FuncOp func,
   Location loc = func.getLoc();
   Value lo = args[loIdx];
   Value hi = args[hiIdx];
+  SmallVector<Type, 2> types(2, lo.getType()); // Only two types.
+
   FlatSymbolRefAttr partitionFunc = getMangledSortHelperFunc(
       builder, func, {IndexType::get(context)}, kPartitionFuncNamePrefix, nx,
       ny, isCoo, args.drop_back(nTrailingP), createPartitionFunc);
@@ -935,14 +944,25 @@ createQuickSort(OpBuilder &builder, ModuleOp module, func::FuncOp func,
                                       TypeRange{IndexType::get(context)},
                                       args.drop_back(nTrailingP))
                 .getResult(0);
-  Value pP1 =
-      builder.create<arith::AddIOp>(loc, p, constantIndex(builder, loc, 1));
+
   Value lenLow = builder.create<arith::SubIOp>(loc, p, lo);
   Value lenHigh = builder.create<arith::SubIOp>(loc, hi, p);
+  // Partition already sorts array with len <= 2
+  Value c2 = constantIndex(builder, loc, 2);
+  Value len = builder.create<arith::SubIOp>(loc, hi, lo);
+  Value lenGtTwo =
+      builder.create<arith::CmpIOp>(loc, arith::CmpIPredicate::ugt, len, c2);
+  scf::IfOp ifLenGtTwo =
+      builder.create<scf::IfOp>(loc, types, lenGtTwo, /*else=*/true);
+  builder.setInsertionPointToStart(&ifLenGtTwo.getElseRegion().front());
+  // Returns an empty range to mark the entire region is fully sorted.
+  builder.create<scf::YieldOp>(loc, ValueRange{lo, lo});
+
+  // Else len > 2, need recursion.
+  builder.setInsertionPointToStart(&ifLenGtTwo.getThenRegion().front());
   Value cond = builder.create<arith::CmpIOp>(loc, arith::CmpIPredicate::ule,
                                              lenLow, lenHigh);
 
-  SmallVector<Type, 2> types(2, lo.getType()); // Only two types.
   scf::IfOp ifOp = builder.create<scf::IfOp>(loc, types, cond, /*else=*/true);
 
   Value c0 = constantIndex(builder, loc, 0);
@@ -961,14 +981,17 @@ createQuickSort(OpBuilder &builder, ModuleOp module, func::FuncOp func,
   // the bigger partition to be processed by the enclosed while-loop.
   builder.setInsertionPointToStart(&ifOp.getThenRegion().front());
   mayRecursion(lo, p, lenLow);
-  builder.create<scf::YieldOp>(loc, ValueRange{pP1, hi});
+  builder.create<scf::YieldOp>(loc, ValueRange{p, hi});
 
   builder.setInsertionPointToStart(&ifOp.getElseRegion().front());
-  mayRecursion(pP1, hi, lenHigh);
+  mayRecursion(p, hi, lenHigh);
   builder.create<scf::YieldOp>(loc, ValueRange{lo, p});
 
   builder.setInsertionPointAfter(ifOp);
-  return std::make_pair(ifOp.getResult(0), ifOp.getResult(1));
+  builder.create<scf::YieldOp>(loc, ifOp.getResults());
+
+  builder.setInsertionPointAfter(ifLenGtTwo);
+  return std::make_pair(ifLenGtTwo.getResult(0), ifLenGtTwo.getResult(1));
 }
 
 /// Creates a function to perform insertion sort on the values in the range of