[llvm] [APFloat] add power (PR #122889)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-adt

Author: Iman Hosseini (ImanHosseini)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/122889.diff


2 Files Affected:

- (modified) llvm/include/llvm/ADT/APFloat.h (+21) 
- (modified) llvm/unittests/ADT/APFloatTest.cpp (+15) 


``````````diff
diff --git a/llvm/include/llvm/ADT/APFloat.h b/llvm/include/llvm/ADT/APFloat.h
index 9792749230cbf9..803949cf9abcbf 100644
--- a/llvm/include/llvm/ADT/APFloat.h
+++ b/llvm/include/llvm/ADT/APFloat.h
@@ -1536,6 +1536,27 @@ inline APFloat abs(APFloat X) {
   return X;
 }
 
+/// Returns X^N for N >= 0.
+/// Returns X^N for N >= 0.
+inline APFloat pow(const APFloat &X, const int &N) {
+  assert(N >= 0 && "negative exponents not supported.");
+  APFloat Acc = APFloat::getOne(X.getSemantics());
+  if (N == 0) {
+    return APFloat::getOne(X.getSemantics());
+  }
+  APFloat Base = X;
+  int64_t RemainingExponent = N;
+  while (RemainingExponent > 0) {
+    while (RemainingExponent % 2 == 0) {
+      Base = Base * Base;
+      RemainingExponent /= 2;
+    }
+    --RemainingExponent;
+    Acc = Acc * Base;
+  }
+  return Acc;
+};
+
 /// Returns the negated value of the argument.
 inline APFloat neg(APFloat X) {
   X.changeSign();
diff --git a/llvm/unittests/ADT/APFloatTest.cpp b/llvm/unittests/ADT/APFloatTest.cpp
index f291c814886d35..0e4fe151af10af 100644
--- a/llvm/unittests/ADT/APFloatTest.cpp
+++ b/llvm/unittests/ADT/APFloatTest.cpp
@@ -3793,6 +3793,21 @@ TEST(APFloatTest, abs) {
   EXPECT_TRUE(PSmallestNormalized.bitwiseIsEqual(abs(MSmallestNormalized)));
 }
 
+TEST(APFloatTest, pow) {
+  APFloat One = APFloat(APFloat::IEEEsingle(), "1.0");
+  APFloat Two = APFloat(APFloat::IEEEsingle(), "2.0");
+  APFloat Four = APFloat(APFloat::IEEEsingle(), "4.0");
+  APFloat Eight = APFloat(APFloat::IEEEsingle(), "8.0");
+  APFloat NegTwo = APFloat(APFloat::IEEEsingle(), "-2.0");
+  APFloat NegEight = APFloat(APFloat::IEEEsingle(), "-8.0");
+
+  EXPECT_TRUE(One.bitwiseIsEqual(pow(One, 0)));
+  EXPECT_TRUE(One.bitwiseIsEqual(pow(One, 3)));
+  EXPECT_TRUE(Four.bitwiseIsEqual(pow(Two, 2)));
+  EXPECT_TRUE(Eight.bitwiseIsEqual(pow(Two, 3)));
+  EXPECT_TRUE(NegEight.bitwiseIsEqual(pow(NegTwo, 3)));
+}
+
 TEST(APFloatTest, neg) {
   APFloat One = APFloat(APFloat::IEEEsingle(), "1.0");
   APFloat NegOne = APFloat(APFloat::IEEEsingle(), "-1.0");

``````````

</details>


https://github.com/llvm/llvm-project/pull/122889