[libc-commits] [libc] [libc][math] Implement atan2f correctly rounded to all rounding modes. (PR #86716)

[Nick Desaulniers via libc-commits]

================
@@ -0,0 +1,132 @@
+//===-- Unittests for atan2f ----------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "include/llvm-libc-macros/math-macros.h"
+#include "src/__support/FPUtil/FPBits.h"
+#include "src/math/atan2f.h"
+#include "test/UnitTest/FPMatcher.h"
+#include "test/UnitTest/Test.h"
+#include "utils/MPFRWrapper/MPFRUtils.h"
+
+using LlvmLibcAtan2fTest = LIBC_NAMESPACE::testing::FPTest<float>;
+using LIBC_NAMESPACE::testing::tlog;
+
+namespace mpfr = LIBC_NAMESPACE::testing::mpfr;
+
+TEST_F(LlvmLibcAtan2fTest, TrickyInputs) {
+  constexpr int N = 17;
+  mpfr::BinaryInput<float> INPUTS[N] = {
+      {0x1.0cb3a4p+20f, 0x1.4ebacp+22f},   {0x1.12215p+1f, 0x1.4fabfcp+22f},
+      {-0x1.13baaep+41f, 0x1.5bd22ep+23f}, {0x1.1ff7dcp+41f, 0x1.aec0a6p+23f},
+      {0x1.2bc794p+23f, 0x1.0bc0c6p+23f},  {0x1.2fba3ap+42f, 0x1.f99456p+23f},
+      {0x1.5ea1f8p+27f, 0x1.f2a1aep+23f},  {0x1.7a931p+44f, 0x1.352ac4p+22f},
+      {0x1.8802bcp+21f, 0x1.8f130ap+23f},  {0x1.658ef8p+17f, 0x1.3c00f4p+22f},
+      {0x1.69fb0cp+21f, 0x1.39e4c4p+23f},  {0x1.8eb24cp+11f, 0x1.36518p+23f},
+      {0x1.9e7ebp+30f, 0x1.d80522p+23f},   {0x1.b4bdeep+19f, 0x1.c19b4p+23f},
+      {0x1.bc201p+43f, 0x1.617346p+23f},   {0x1.c96c3cp+20f, 0x1.c01d1ep+23f},
+      {0x1.781fcp+28f, 0x1.dcb3cap+23f},
+  };
+
+  for (int i = 0; i < N; ++i) {
+    float x = INPUTS[i].x;
+    float y = INPUTS[i].y;
+    ASSERT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Atan2, INPUTS[i],
+                                   LIBC_NAMESPACE::atan2f(x, y), 0.5);
+    INPUTS[i].x = -INPUTS[i].x;
+    ASSERT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Atan2, INPUTS[i],
+                                   LIBC_NAMESPACE::atan2f(-x, y), 0.5);
+    INPUTS[i].y = -INPUTS[i].y;
+    ASSERT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Atan2, INPUTS[i],
+                                   LIBC_NAMESPACE::atan2f(-x, -y), 0.5);
+    INPUTS[i].x = -INPUTS[i].x;
+    ASSERT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Atan2, INPUTS[i],
+                                   LIBC_NAMESPACE::atan2f(x, -y), 0.5);
+  }
+}
+
+TEST_F(LlvmLibcAtan2fTest, InFloatRange) {
+  constexpr uint32_t X_COUNT = 1'23;
+  constexpr uint32_t X_START = FPBits(0.25f).uintval();
+  constexpr uint32_t X_STOP = FPBits(4.0f).uintval();
+  constexpr uint32_t X_STEP = (X_STOP - X_START) / X_COUNT;
+
+  constexpr uint32_t Y_COUNT = 1'37;
+  constexpr uint32_t Y_START = FPBits(0.25f).uintval();
+  constexpr uint32_t Y_STOP = FPBits(4.0f).uintval();
+  constexpr uint32_t Y_STEP = (Y_STOP - Y_START) / Y_COUNT;
+
+  auto test = [&](mpfr::RoundingMode rounding_mode) {
+    mpfr::ForceRoundingMode __r(rounding_mode);
+    if (!__r.success)
+      return;
+
+    uint64_t fails = 0;
+    uint64_t count = 0;
+    uint64_t cc = 0;
+    float mx, my, mr = 0.0;
+    double tol = 0.5;
----------------
nickdesaulniers wrote:

Not really sure what `cc` or `tol` is shorthand for. Consider giving these more descriptive identifiers.

https://github.com/llvm/llvm-project/pull/86716