From 91c1d9b51af3fa79ff604207eae787c2638d93a3 Mon Sep 17 00:00:00 2001
From: Giulio Eulisse <10544+ktf@users.noreply.github.com>
Date: Wed, 16 Sep 2026 15:10:12 +0200
Subject: [PATCH 1/2] TPC: place shared constants in the Metal constant address
 space

MSL requires namespace-scope constexpr to live in the constant address space.
Generic pointers do not help here: constant is explicitly not among the
address spaces MSL 4.1 makes generic, so the annotation is required whatever
the language version. Guarded on __METAL__, so no other build changes.
---
 .../Detectors/TPC/include/DataFormatsTPC/Constants.h   | 10 ++++++----
 GPU/Common/GPUCommonDefAPI.h                           |  5 +++++
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/DataFormats/Detectors/TPC/include/DataFormatsTPC/Constants.h b/DataFormats/Detectors/TPC/include/DataFormatsTPC/Constants.h
index 0ddf7281be866..c5423420d9fec 100644
--- a/DataFormats/Detectors/TPC/include/DataFormatsTPC/Constants.h
+++ b/DataFormats/Detectors/TPC/include/DataFormatsTPC/Constants.h
@@ -17,6 +17,8 @@
 #ifndef AliceO2_TPC_Constants_H
 #define AliceO2_TPC_Constants_H
 
+#include "GPUCommonDef.h"
+
 namespace o2
 {
 namespace tpc
@@ -25,17 +27,17 @@ namespace constants
 {
 
 // the number of sectors
-constexpr int MAXSECTOR = 36;
+GPUglobalconstexpr() int MAXSECTOR = 36;
 
 // the number of global pad rows
 #if defined(GPUCA_STANDALONE) && defined(GPUCA_RUN2)
-constexpr int MAXGLOBALPADROW = 159; // Number of pad rows in Run 2, used for GPU TPC tests with Run 2 data
+GPUglobalconstexpr() int MAXGLOBALPADROW = 159; // Number of pad rows in Run 2, used for GPU TPC tests with Run 2 data
 #else
-constexpr int MAXGLOBALPADROW = 152; // Correct number of pad rows in Run 3
+GPUglobalconstexpr() int MAXGLOBALPADROW = 152; // Correct number of pad rows in Run 3
 #endif
 
 // number of LHC bunch crossings per TPC time bin (40 MHz / 5 MHz)
-constexpr int LHCBCPERTIMEBIN = 8;
+GPUglobalconstexpr() int LHCBCPERTIMEBIN = 8;
 } // namespace constants
 } // namespace tpc
 } // namespace o2
diff --git a/GPU/Common/GPUCommonDefAPI.h b/GPU/Common/GPUCommonDefAPI.h
index 45cc987453830..61a12989481d1 100644
--- a/GPU/Common/GPUCommonDefAPI.h
+++ b/GPU/Common/GPUCommonDefAPI.h
@@ -48,6 +48,7 @@
   #define GPUglobal()                               // global memory variable declaration (only used for kernel input pointers)
   #define GPUconstant()                             // constant memory variable declaraion
   #define GPUconstexpr() static constexpr           // constexpr on GPU that needs to be instantiated for dynamic access (e.g. arrays), becomes __constant on GPU
+  #define GPUglobalconstexpr() constexpr            // constexpr variable at program scope, needs the constant address space in MSL
   #define GPUprivate()                              // private memory variable declaration
   #define GPUgeneric()                              // reference / ptr to generic address space
   #define GPUbarrier()                              // synchronize all GPU threads in block
@@ -160,6 +161,7 @@
   #define GPUglobal() device
   #define GPUconstant() constant // TODO: possibly add const __restrict where possible later!
   #define GPUconstexpr() constant
+  #define GPUglobalconstexpr() constant constexpr
   #define GPUprivate() thread
   #define GPUgeneric()
   #define GPUglobalref() device
@@ -255,6 +257,9 @@
 #ifndef GPUconstexprref
 #define GPUconstexprref()
 #endif
+#ifndef GPUglobalconstexpr
+#define GPUglobalconstexpr() constexpr
+#endif
 
 #define GPUrestrict() __restrict__
 

From 943417683999244feaae3dc1a87a47cbfb4992f8 Mon Sep 17 00:00:00 2001
From: ALICE Action Bot <alibuild@cern.ch>
Date: Wed, 16 Sep 2026 13:11:57 +0000
Subject: [PATCH 2/2] Please consider the following formatting changes

---
 GPU/Common/GPUCommonDefAPI.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/GPU/Common/GPUCommonDefAPI.h b/GPU/Common/GPUCommonDefAPI.h
index 61a12989481d1..a04934304d525 100644
--- a/GPU/Common/GPUCommonDefAPI.h
+++ b/GPU/Common/GPUCommonDefAPI.h
@@ -282,5 +282,5 @@
   #define get_group_id(dim) iBlock
 #endif
 
-// clang-format on
+    // clang-format on
 #endif