[Mlir-commits] [mlir] [MLIR][Transforms] add eliminate-explicit-rounding pass (PR #93443)

[Mehdi Amini]

================
@@ -0,0 +1,62 @@
+//===- EliminateExplicitRounding.cpp - Remove intermediate extf/truncf pairs
+//-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements removing intermediate extf/truncf pairs inserted from
+// type conversion.
+//
+//===----------------------------------------------------------------------===//
+#include "mlir/Dialect/Arith/Transforms/Passes.h"
+
+#include "mlir/Dialect/Arith/IR/Arith.h"
+#include "mlir/IR/PatternMatch.h"
+#include "mlir/IR/TypeUtilities.h"
+#include "mlir/Transforms/GreedyPatternRewriteDriver.h"
+
+namespace mlir {
+namespace arith {
+#define GEN_PASS_DEF_ARITHELIMINATEEXPLICITROUNDING
+#include "mlir/Dialect/Arith/Transforms/Passes.h.inc"
+} // namespace arith
+} // namespace mlir
+
+using namespace mlir;
+
+namespace {
+
+struct EliminateExplicitRounding final
+    : arith::impl::ArithEliminateExplicitRoundingBase<
+          EliminateExplicitRounding> {
+  using ArithEliminateExplicitRoundingBase::ArithEliminateExplicitRoundingBase;
+  void runOnOperation() override {
+    getOperation()->walk([&](arith::ExtFOp extFOp) {
+      // Check whether match `truncF->extF` pair.
+      auto truncFOp = extFOp.getOperand().getDefiningOp<arith::TruncFOp>();
+      if (truncFOp) {
+        // Check whether the rounding pair's input and output data type are the
+        // same. Currently only consider to eliminate rounding pairs for (bf16 /
+        // f16
+        // <-> f32).
+        Value input = truncFOp.getOperand();
+        Type inTy = getElementTypeOrSelf(input.getType());
+        Type outTy = getElementTypeOrSelf(extFOp.getType());
+        Type shortTy = getElementTypeOrSelf(truncFOp.getType());
+        if (isa<Float32Type>(inTy) && isa<Float32Type>(outTy) &&
+            (isa<Float16Type, BFloat16Type>(shortTy))) {
+          for (auto &use :
+               llvm::make_early_inc_range(extFOp.getResult().getUses())) {
+            use.set(input);
+          }
----------------
joker-eph wrote:

Isn't this equivalent to the follow?

```suggestion
          extFOp.replaceAllUsesWith(input);
```

https://github.com/llvm/llvm-project/pull/93443