cc.cmake assumes GCC_VERSION, causing build failure with NVHPC

[antoine-morvan]

Hello,

I am trying to build OpenBLAS with NVHPC on anIntel Sapphire Rapids system, and I am running into issues in cc.cmake.

With this setup, the following section is triggered:

OpenBLAS/cmake/cc.cmake

Lines 188 to 198 in 02dc625

	if (${CORE} STREQUAL SAPPHIRERAPIDS)
	if (NOT DYNAMIC_ARCH)
	if (NOT NO_AVX512)
	if (${GCC_VERSION} VERSION_GREATER 11.0 OR ${GCC_VERSION} VERSION_EQUAL 11.0)
	set (CCOMMON_OPT "${CCOMMON_OPT} -march=sapphirerapids")
	else ()
	set (CCOMMON_OPT "${CCOMMON_OPT} -march=skylake-avx512")
	endif()
	endif ()
	endif ()
	endif ()

However, when building with NVHPC, $GCC_VERSION is not defined. As a result CMake fails with an error like this :

CMake Error at cmake/cc.cmake:191 (if):
  if given arguments:

    "VERSION_GREATER" "11.0" "OR" "VERSION_EQUAL" "11.0"

  Unknown arguments specified

It seems that this condition assumes a GNU compiler, and should probably only be evaluated when that is the case.

I believe similar issues may occur for other microarchitectures, such as:

• cooperlake :

  OpenBLAS/cmake/cc.cmake

  Line 179 in 02dc625

  if (${GCC_VERSION} VERSION_GREATER 10.1 OR ${GCC_VERSION} VERSION_EQUAL 10.1)

• zen :

  OpenBLAS/cmake/cc.cmake

  Line 204 in 02dc625

  if (${GCC_VERSION} VERSION_GREATER 13.0 OR ${GCC_VERSION} VERSION_EQUAL 13.0)

• a64fx when disabling SVE :

  OpenBLAS/cmake/cc.cmake

  Line 218 in 02dc625

  elseif (${GCC_VERSION} VERSION_GREATER 11.0 OR ${GCC_VERSION} VERSION_EQUAL 11.0)

  
  etc.

Whike looking further into the file, I also noticed that $GCC_VERSION is set even when the compiler is Intel LLVM :

OpenBLAS/cmake/cc.cmake

Line 36 in 02dc625

set(GCC_VERSION 100)

This might contribute to inconsistent behavior accross compiler, and most likely implies missuse of this variable (testing against this value) somewhere else in the CMake files.

Best.

[martin-frbg]

For the Intel compiler, GCC_VERSION is simply set to a ridiculously large value to make the GCC-specific version checks irrelevant (any version is expected to support the respective cpu models).
NVHPC should probably get specific conditionals in the individual x86_64 cpu sections (as already implemented for arm64), but setting GCC_VERSION to the same absurd value should work as well (thanks to NVHPC accepting the -march option as an alias for its -tp)