[Libomptarget][NFC] Remove constexpr to hide warnings

[jhuber6]

Summary

Currently whenever we compile the device runtime we get the following
'Mapping.cpp:32:32: warning: inline function '_OMP::impl::getGridValue'
is not defined [-Wundefined-inline]' warning. This can be silenced by
removing the constexpr attribute for this function. Doing this doesn't
change the generated bitcode at all but prevents the screen from getting
filled with warnings whenver we build the runtime.

[jdoerfert]

LG

[JonChesterfield]

Nvm, saw the commit message

This is a variant thing iiuc. Can we fix the warning without losing the O0 compile time constant by defining a non-variant version of this function?

[jhuber6]

In D119747#3320903, @JonChesterfield wrote:

Nvm, saw the commit message

This is a variant thing iiuc. Can we fix the warning without losing the O0 compile time constant by defining a non-variant version of this function?

Says so in the commit message Mapping.cpp:32:32: warning: inline function '_OMP::impl::getGridValue' is not defined [-Wundefined-inline]. I'm not sure why it happened here. Might be some weird interaction with variant or something, I just wanted to stop getting these warnings every time I built the runtime and this was the easiest way.

openmp/libomptarget/DeviceRTL/src/Mapping.cpp

 namespace _OMP {
 namespace impl {
 
 /// AMDGCN Implementation
 ///
 ///{
 #pragma omp begin declare variant match(device = {arch(amdgcn)})
 
-constexpr const llvm::omp::GV &getGridValue() {
+static const llvm::omp::GV &getGridValue() {
   return llvm::omp::getAMDGPUGridValues<__AMDGCN_WAVEFRONT_SIZE>();
 }
 
 uint32_t getGridDim(uint32_t n, uint16_t d) {
   uint32_t q = n / d;
   return q + (n > q * d);
 }
 

 ///{
 #pragma omp begin declare variant match(                                       \
     device = {arch(nvptx, nvptx64)}, implementation = {extension(match_any)})
 
 uint32_t getNumHardwareThreadsInBlock() {
   return __nvvm_read_ptx_sreg_ntid_x();
 }
 
-constexpr const llvm::omp::GV &getGridValue() {
+static const llvm::omp::GV &getGridValue() {
   return llvm::omp::NVPTXGridValues;
 }
 
 LaneMaskTy activemask() {
   unsigned int Mask;
   asm("activemask.b32 %0;" : "=r"(Mask));
   return Mask;
 }