From 31a681d15f6925eca4dac2010074fccac26035be Mon Sep 17 00:00:00 2001
From: Ferdinand Lemaire <ferdinan@xilinx.com>
Date: Tue, 9 Jul 2024 16:07:54 +0100
Subject: [PATCH] Allow log2 pdll builtin to return a floating point value even
 if the log2 is not exact

---
 mlir/lib/Dialect/PDL/IR/Builtins.cpp       |  2 +-
 mlir/unittests/Dialect/PDL/BuiltinTest.cpp | 12 ++++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/mlir/lib/Dialect/PDL/IR/Builtins.cpp b/mlir/lib/Dialect/PDL/IR/Builtins.cpp
index b8e1d9c87c0918..33216c1a0cef27 100644
--- a/mlir/lib/Dialect/PDL/IR/Builtins.cpp
+++ b/mlir/lib/Dialect/PDL/IR/Builtins.cpp
@@ -169,7 +169,7 @@ LogicalResult static unaryOp(PatternRewriter &rewriter, PDLResultList &results,
     } else if constexpr (T == UnaryOpKind::log2) {
       results.push_back(rewriter.getFloatAttr(
           operandFloatAttr.getType(),
-          (double)operandFloatAttr.getValue().getExactLog2()));
+          std::log2(operandFloatAttr.getValueAsDouble())));
     } else if constexpr (T == UnaryOpKind::abs) {
       auto resultVal = operandFloatAttr.getValue();
       resultVal.clearSign();
diff --git a/mlir/unittests/Dialect/PDL/BuiltinTest.cpp b/mlir/unittests/Dialect/PDL/BuiltinTest.cpp
index a86c08e78e923c..7413f0bffa0d82 100644
--- a/mlir/unittests/Dialect/PDL/BuiltinTest.cpp
+++ b/mlir/unittests/Dialect/PDL/BuiltinTest.cpp
@@ -634,6 +634,18 @@ TEST_F(BuiltinTest, log2) {
         cast<FloatAttr>(result.cast<Attribute>()).getValue().convertToFloat(),
         2.0);
   }
+  
+  auto threeF16 = rewriter.getF16FloatAttr(3.0);
+
+  // check correctness
+  {
+    TestPDLResultList results(1);
+    EXPECT_TRUE(builtin::log2(rewriter, results, {threeF16}).succeeded());
+
+    PDLValue result = results.getResults()[0];
+    float resultVal = cast<FloatAttr>(result.cast<Attribute>()).getValue().convertToFloat();
+    EXPECT_TRUE(resultVal > 1.58 && resultVal < 1.59);
+  }
 }
 
 TEST_F(BuiltinTest, exp2) {