[Bf-blender-cvs] [35bfe1702c3] master: BLI: add safe_powf function

[Jacques Lucke]

Commit: 35bfe1702c3754af17f440c7ee7cb0e9abb8fa9d
Author: Jacques Lucke
Date:   Thu Jul 16 10:46:18 2020 +0200
Branches: master
https://developer.blender.org/rB35bfe1702c3754af17f440c7ee7cb0e9abb8fa9d

BLI: add safe_powf function

The same function is also used by cycles.

===================================================================

M	source/blender/blenlib/BLI_math_base.h
M	source/blender/blenlib/intern/math_base_inline.c
M	tests/gtests/blenlib/BLI_math_base_test.cc

===================================================================

diff --git a/source/blender/blenlib/BLI_math_base.h b/source/blender/blenlib/BLI_math_base.h
index c456ab0ecef..49aa9f3b465 100644
--- a/source/blender/blenlib/BLI_math_base.h
+++ b/source/blender/blenlib/BLI_math_base.h
@@ -103,6 +103,7 @@ MINLINE float pow2f(float x);
 MINLINE float pow3f(float x);
 MINLINE float pow4f(float x);
 MINLINE float pow7f(float x);
+MINLINE float safe_powf(float base, float exponent);
 
 MINLINE float sqrt3f(float f);
 MINLINE double sqrt3d(double d);
diff --git a/source/blender/blenlib/intern/math_base_inline.c b/source/blender/blenlib/intern/math_base_inline.c
index 1b388dcf11f..26dc4d35c80 100644
--- a/source/blender/blenlib/intern/math_base_inline.c
+++ b/source/blender/blenlib/intern/math_base_inline.c
@@ -70,6 +70,13 @@ MINLINE float pow7f(float x)
 {
   return pow2f(pow3f(x)) * x;
 }
+MINLINE float safe_powf(float base, float exponent)
+{
+  if (UNLIKELY(base < 0.0f && exponent != (int)exponent)) {
+    return 0.0f;
+  }
+  return powf(base, exponent);
+}
 
 MINLINE float sqrt3f(float f)
 {
diff --git a/tests/gtests/blenlib/BLI_math_base_test.cc b/tests/gtests/blenlib/BLI_math_base_test.cc
index dc20c75576d..b7e7472eab2 100644
--- a/tests/gtests/blenlib/BLI_math_base_test.cc
+++ b/tests/gtests/blenlib/BLI_math_base_test.cc
@@ -113,3 +113,15 @@ TEST(math_base, Log2CeilU)
   EXPECT_EQ(log2_ceil_u(9), 4);
   EXPECT_EQ(log2_ceil_u(123456), 17);
 }
+
+TEST(math_base, SafePowf)
+{
+  EXPECT_FLOAT_EQ(safe_powf(4.0f, 3.0f), 64.0f);
+  EXPECT_FLOAT_EQ(safe_powf(3.2f, 5.6f), 674.2793796f);
+  EXPECT_FLOAT_EQ(safe_powf(4.0f, -2.0f), 0.0625f);
+  EXPECT_FLOAT_EQ(safe_powf(6.0f, -3.2f), 0.003235311f);
+  EXPECT_FLOAT_EQ(safe_powf(-4.0f, 6), 4096.0f);
+  EXPECT_FLOAT_EQ(safe_powf(-3.0f, 5.5), 0.0f);
+  EXPECT_FLOAT_EQ(safe_powf(-2.5f, -4.0f), 0.0256f);
+  EXPECT_FLOAT_EQ(safe_powf(-3.7f, -4.5f), 0.0f);
+}