CommonConstants: place shared constants in the constant address space

MSL requires every variable at program scope to name an address space and
diagnoses it at the declaration, so these headers broke any device translation
unit that included them. GPUglobalconstexpr() expands to constexpr everywhere
except Metal, where it adds constant.

Preprocessed declarations are unchanged for host, CUDA, HIP and cling.

Author: ktf

Common/Constants/CMakeLists.txt

@@ -9,4 +9,5 @@
 # granted to it by virtue of its status as an Intergovernmental Organization
 # or submit itself to any jurisdiction.
 
-o2_add_header_only_library(CommonConstants)
+o2_add_header_only_library(CommonConstants
+                           INTERFACE_LINK_LIBRARIES O2::GPUCommon)

Common/Constants/include/CommonConstants/LHCConstants.h

@@ -16,6 +16,8 @@
 #ifndef ALICEO2_LHCCONSTANTS_H_
 #define ALICEO2_LHCCONSTANTS_H_
 
+#include "GPUCommonDef.h"
+
 namespace o2
 {
 namespace constants
@@ -28,17 +30,17 @@ enum BeamDirection : int { BeamA, // beamA = beam 0,
                            NBeamDirections,
                            InteractingBC = -1 // as used in the BunchFilling class
 };
-constexpr int LHCMaxBunches = 3564;                              // max N bunches
+GPUglobalconstexpr() int LHCMaxBunches = 3564;                   // max N bunches
 constexpr double LHCRFFreq = 400.789e6;                          // LHC RF frequency in Hz
 constexpr double LHCBunchSpacingNS = 10 * 1.e9 / LHCRFFreq;      // bunch spacing in ns (10 RFbuckets)
 constexpr double LHCOrbitNS = LHCMaxBunches * LHCBunchSpacingNS; // orbit duration in ns
 constexpr double LHCRevFreq = 1.e9 / LHCOrbitNS;                 // revolution frequency
 constexpr double LHCBunchSpacingMUS = LHCBunchSpacingNS * 1e-3;  // bunch spacing in \mus (10 RFbuckets)
 constexpr double LHCOrbitMUS = LHCOrbitNS * 1e-3;                // orbit duration in \mus
-constexpr unsigned int MaxNOrbits = 0xffffffff;
+GPUglobalconstexpr() unsigned int MaxNOrbits = 0xffffffff;
 
 // Offsets of A, C beam bunches at P2
-constexpr int BunchOffsetsP2[2] = {344, 3017};
+GPUglobalconstexpr() int BunchOffsetsP2[2] = {344, 3017};
 
 // convert LHC bunch ID to BC for 2 beam directions
 constexpr int LHCBunch2P2BC(int bunch, BeamDirection dir)

Common/Constants/include/CommonConstants/MathConstants.h

@@ -16,31 +16,33 @@
 #ifndef ALICEO2_COMMON_MATH_CONSTANTS_
 #define ALICEO2_COMMON_MATH_CONSTANTS_
 
+#include "GPUCommonDef.h"
+
 namespace o2
 {
 namespace constants
 {
 namespace math
 {
-constexpr float Almost0 = 0x1.0p-126f;   // smallest non-denormal float
-constexpr float Epsilon = 0x0.000002p0f; // smallest float such that 1 != 1 + Epsilon
-constexpr float Almost1 = 1.f - 1.0e-6f;
-constexpr float VeryBig = 1.f / Almost0;
+GPUglobalconstexpr() float Almost0 = 0x1.0p-126f;   // smallest non-denormal float
+GPUglobalconstexpr() float Epsilon = 0x0.000002p0f; // smallest float such that 1 != 1 + Epsilon
+GPUglobalconstexpr() float Almost1 = 1.f - 1.0e-6f;
+GPUglobalconstexpr() float VeryBig = 1.f / Almost0;
 
-constexpr float PI = 3.14159274101257324e+00f;
-constexpr float TwoPI = 2.f * PI;
-constexpr float PIHalf = 0.5f * PI;
-constexpr float PIThird = PI / 3.0f;
-constexpr float PIQuarter = 0.25f * PI;
-constexpr float Rad2Deg = 180.f / PI;
-constexpr float Deg2Rad = PI / 180.f;
+GPUglobalconstexpr() float PI = 3.14159274101257324e+00f;
+GPUglobalconstexpr() float TwoPI = 2.f * PI;
+GPUglobalconstexpr() float PIHalf = 0.5f * PI;
+GPUglobalconstexpr() float PIThird = PI / 3.0f;
+GPUglobalconstexpr() float PIQuarter = 0.25f * PI;
+GPUglobalconstexpr() float Rad2Deg = 180.f / PI;
+GPUglobalconstexpr() float Deg2Rad = PI / 180.f;
 
-constexpr int NSectors = 18;
-constexpr float SectorSpanDeg = 360. / NSectors;
-constexpr float SectorSpanRad = SectorSpanDeg * Deg2Rad;
+GPUglobalconstexpr() int NSectors = 18;
+GPUglobalconstexpr() float SectorSpanDeg = 360. / NSectors;
+GPUglobalconstexpr() float SectorSpanRad = SectorSpanDeg * Deg2Rad;
 
 // conversion from B(kGaus) to curvature for 1GeV pt
-constexpr float B2C = -0.299792458e-3;
+GPUglobalconstexpr() float B2C = -0.299792458e-3;
 } // namespace math
 } // namespace constants
 } // namespace o2