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cpeAMD toolchain

Note: The options are for the file included in this repository and are not the same as those for the repository at CSCS.

Note about the compilers

  • AMD/ROCm 5.0.2 is based on LLVM 14.0.0

Available options

The cpeAMD toolchain supports the common toolchain options, the additional AMD flags and some additional Cray-specific flags, two of which are really just redefinitions of standard compiler flags.

Default toolchain options that may not behave as expected

  • rpath: rpath linking in EasyBuild has not been properly tested in the HPE Cray PE.

  • unroll: As it is not clear from the docunentation for the Fortran compiler which options should be set to enable or disable (if any at all)

AMD-specific toolchain options

Option Categorie What?
lto code generation Enable Link Time Optimization (in the default 'full' mode)
offload-lto code generation Enable LTO for offload compilation (in the default 'full' mode)

cpeAMD-specific flags (coming from the HPE Cray PE compiler wrappers)

Option Categorie What?
dynamic code generation Generate dynamically linked executable (default: True)
mpich-mt parallelism Alternate Cray-MPICH library for MT support (default: False)

mpich-mt: Directs the driver to link in an alternate version of the Cray-MPICH library which provides fine-grained multi-threading support to applications that perform MPI operations within threaded regions. (default: False)

Two further options trigger different compiler flags than in the GCC toolchain: verbose and optarch but have otherwise the same meaning.

Mapping of options onto compiler flags

Compiler optimization level

The common options translate into:

Option Flag
noopt -O0
lowopt -O1
defaultopt -O2 -fvectorize -fslp-vectorize
opt -O3

Other optimization-related options (and see also parallelism below):

Option Flag
unroll -funroll-loops
optarch TODO

Floating point precision

The decision of our mapping is based partly on information from Cray and partly on looking through various manuals on Clang.

  • Level strict: We simply stick to -ffp-model=strict. This automatically disables all of the -ffast-math enablements so there is no need to add -fno-fast-math. Note that at this level, fused multiply adds are disabled.
  • Level precise: We stick to -ffp-model=precise and add -ffp-contract=fast-honor-pragmas.
  • Default level: Currently the same as strict.
  • Level loose: Set to -ffp-model=fast but try to turn on again a few safeguards: -ffp-contract=fast-honor-pragmas, -fhonor-infinities, -fhonor-nans, -fsigned-zeros.
  • Level veryloose: Set to -ffp-model=fast

Note: Very recnet versions of clang add -ffp-contract=fast-honor-pragmas which may be interesting to add to precise, defaultprec and loose but is not yet supported by AOCC 2.2.

Option Flag
strict -ffp-model=strict
precise -ffp-model=precise
defaultprec -ffp-model=precise
loose -ffp-model=fast -fhonor-infinities -fhonor-nans -fsigned-zeros
veryloose -ffp-model=fast

Other floating-point optimisation and accuracy-related flags:

Option What?
ieee Not supported in clang/flang
Option Flag
vectorize False: -fno-vectorize -fno-slp-vectorize
True: -fvectorize -fslp-vectorize
loop -ftree-switch-conversion -floop-interchange -floop-strip-mine -floop-block
openmp -fopenmp
usempi No compiler flags
mpich-mt -craympich-mt

Code generation and linking options

Option Flag
dynamic No flag as this is currently the only mode supported
lto -flto
offload-lto -foffload-lto
32bit -m32
debug -g
pic -fPIC
packed-linker-options Pack the linker options as comma separated list (default: False)
shared -shared
static -static
rpath Use RPATH wrappers when --rpath is enabled in EasyBuild configuration (default: True)

NOTE: rpath has not yet been checked and is likely broken. There is a better way to do this in the /hPE Cray PE than what EasyBuild does as the wrappers already support rpath linking.

Option Flag
cstd -std=%(value)s
i8 -fdefault-integer-8
r8 -fdefault-real-8
f2c -ff2c

Miscellaneous options

Option Flag
verbose -craype-verbose