OPENMP and __GNUC__ compiler safety and performance

As references see darktable-org#18729 darktable-org#18975 and
https://bugzilla.redhat.com/show_bug.cgi?id=2362561 see late comments there from Jakub Jelinek
https://bugzilla.redhat.com/show_bug.cgi?id=2368336
https://bugzilla.redhat.com/show_bug.cgi?id=2373291

Author: jenshannoschwalm

src/develop/openmp_maths.h

@@ -23,44 +23,41 @@
 #pragma once
 
 
-#if defined(_OPENMP) && !defined(_WIN32) && (!defined(__GNUC__) || __GNUC__ >= 12)
+#if defined(_OPENMP) && !defined(_WIN32) && !defined(__GNUC__)
+  // GCC and CLANG have declarations in standard headers if and only if the architecture and compile options support vectorization, so
+  // don't try to override that here - causes dynamic-link errors at startup.
+  DT_OMP_DECLARE_SIMD()
+  extern float fmaxf(const float x, const float y);
 
-#ifndef __GNUC__  // GCC 12 compiles but fails at runtime due to missing library function
-DT_OMP_DECLARE_SIMD()
-extern float fmaxf(const float x, const float y);
-#endif
+  DT_OMP_DECLARE_SIMD()
+  extern float fminf(const float x, const float y);
 
-#ifndef __GNUC__  // GCC 12 compiles but fails at runtime due to missing library function
-DT_OMP_DECLARE_SIMD()
-extern float fminf(const float x, const float y);
-#endif
+  DT_OMP_DECLARE_SIMD()
+  extern float fabsf(const float x);
 
-DT_OMP_DECLARE_SIMD()
-extern float fabsf(const float x);
-
-DT_OMP_DECLARE_SIMD()
-extern float powf(const float x, const float y);
+  DT_OMP_DECLARE_SIMD()
+  extern float powf(const float x, const float y);
 
-DT_OMP_DECLARE_SIMD()
-extern float sqrtf(const float x);
+  DT_OMP_DECLARE_SIMD()
+  extern float sqrtf(const float x);
 
-DT_OMP_DECLARE_SIMD()
-extern float cbrtf(const float x);
+  DT_OMP_DECLARE_SIMD()
+  extern float cbrtf(const float x);
 
-DT_OMP_DECLARE_SIMD()
-extern float log2f(const float x);
+  DT_OMP_DECLARE_SIMD()
+  extern float log2f(const float x);
 
-DT_OMP_DECLARE_SIMD()
-extern float exp2f(const float x);
+  DT_OMP_DECLARE_SIMD()
+  extern float exp2f(const float x);
 
-DT_OMP_DECLARE_SIMD()
-extern float log10f(const float x);
+  DT_OMP_DECLARE_SIMD()
+  extern float log10f(const float x);
 
-DT_OMP_DECLARE_SIMD()
-extern float expf(const float x);
+  DT_OMP_DECLARE_SIMD()
+  extern float expf(const float x);
 
-DT_OMP_DECLARE_SIMD()
-extern float logf(const float x);
+  DT_OMP_DECLARE_SIMD()
+  extern float logf(const float x);
 
 #endif
 

src/iop/rawdenoise.c

@@ -1,6 +1,6 @@
 /*
     This file is part of darktable,
-    Copyright (C) 2011-2024 darktable developers.
+    Copyright (C) 2011-2025 darktable developers.
 
 
     darktable is free software: you can redistribute it and/or modify
@@ -226,7 +226,7 @@ static void wavelet_denoise(const float *const restrict in, float *const restric
       const float *const restrict inp = in + (size_t)row * roi->width + offset;
       const int senselwidth = (roi->width-offset+1)/2;
       for(int col = 0; col < senselwidth; col++)
-        fimgp[col] = sqrtf(fmaxf(0.0f, inp[2*col]));
+        fimgp[col] = sqrtf(MAX(0.0f, inp[2*col]));
     }
 
     // perform the wavelet decomposition and denoising