Move Quantization -> Dialect/QuantOps, FxpMathOps -> Dialect/FxpMathOps.

    Adding the additional layer of directory was discussed offline and matches the Target/ tree. The names match the defacto convention we seem to be following where the C++ namespace is ^(.+)Ops/$ matched against the directory name.

    This is in preparation for patching the Quantizer into this tree, which would have been confusing without moving the Quantization dialect to its more proper home. It is left to others to move other dialects if desired.

    Tested:
      ninja check-mlir

--

PiperOrigin-RevId: 248171982

1 files changed, 109 insertions, 0 deletions

diff --git a/mlir/lib/Dialect/QuantOps/Utils/FakeQuantSupport.cpp b/mlir/lib/Dialect/QuantOps/Utils/FakeQuantSupport.cpp
new file mode 100644
index 00000000000..5562e45bb4a
--- /dev/null
+++ b/mlir/lib/Dialect/QuantOps/Utils/FakeQuantSupport.cpp
@@ -0,0 +1,109 @@
+//===- FakeQuantSupport.cpp - Support utilities for FakeQuant ops ---------===//
+//
+// Copyright 2019 The MLIR Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// =============================================================================
+
+#include "mlir/Dialect/QuantOps/FakeQuantSupport.h"
+#include "mlir/Dialect/QuantOps/QuantTypes.h"
+
+using namespace mlir;
+using namespace mlir::quant;
+
+UniformQuantizedType mlir::quant::fakeQuantAttrsToType(Location loc,
+                                                       unsigned numBits,
+                                                       double rmin, double rmax,
+                                                       bool narrowRange,
+                                                       Type expressedType) {
+  MLIRContext *ctx = expressedType.getContext();
+  Type storageType;
+  unsigned flags;
+  int64_t qmin;
+  int64_t qmax;
+
+  // Hard-coded type mapping from TFLite.
+  if (numBits <= 8) {
+    storageType = IntegerType::get(8, ctx);
+    flags = 0;
+    qmin = 0;
+    qmax = 255;
+  } else if (numBits <= 16) {
+    storageType = IntegerType::get(16, ctx);
+    flags = QuantizationFlags::Signed;
+    qmin = -32768;
+    qmax = 32767;
+  } else {
+    ctx->emitError(loc, "unsupported FakeQuant number of bits: ") << numBits;
+    return nullptr;
+  }
+
+  // Handle narrowRange.
+  if (narrowRange) {
+    qmin += 1;
+  }
+
+  // Range must straddle zero.
+  if (rmin > 0.0 || rmax < 0.0) {
+    return (ctx->emitError(loc, "FakeQuant range must straddle zero: [")
+                << rmin << "," << rmax << "]",
+            nullptr);
+  }
+
+  // Special case where min/max is a point. Must be 0.
+  if (rmin == rmax) {
+    return UniformQuantizedType::getChecked(flags, storageType, expressedType,
+                                            0.0, 0, qmin, qmax, loc);
+  }
+
+  // Determine the scale.
+  const double qminDouble = qmin;
+  const double qmaxDouble = qmax;
+  const double scale = (rmax - rmin) / (qmaxDouble - qminDouble);
+
+  // Zero point computation.
+  // In float, solve the affine equation for any known pair
+  // (real value, corresponding quantized value), of which, two such pairs
+  // are known: (rmin, qmin), (rmax, qmax).
+  // The arithmetic error on the zero point computed from either pair will be
+  // roughly machine_epsilon * (sum of absolute values of terms).
+  // Use the variant that adds the smaller error.
+  const double zeroPointFromMin = qminDouble - rmin / scale;
+  const double zeroPointFromMinError =
+      std::abs(qminDouble) + std::abs(rmin / scale);
+  const double zeroPointFromMax = qmaxDouble - rmax / scale;
+  const double zeroPointFromMaxError =
+      std::abs(qmaxDouble) + std::abs(rmax / scale);
+
+  const double zeroPointDouble = (zeroPointFromMinError < zeroPointFromMaxError)
+                                     ? zeroPointFromMin
+                                     : zeroPointFromMax;
+
+  // Now nudge the zero point to be an integer.
+  int64_t nudgedZeroPoint = 0;
+  if (zeroPointDouble < qminDouble) {
+    nudgedZeroPoint = qmin;
+  } else if (zeroPointDouble > qmaxDouble) {
+    nudgedZeroPoint = qmax;
+  } else {
+    nudgedZeroPoint = round(zeroPointDouble);
+  }
+
+  // By construction, the nudged zero point should always be in range.
+  assert(nudgedZeroPoint >= qmin);
+  assert(nudgedZeroPoint <= qmax);
+
+  return UniformQuantizedType::getChecked(flags, storageType, expressedType,
+                                          scale, nudgedZeroPoint, qmin, qmax,
+                                          loc);
+}