This set of patches addresses some deficiencies in the way the OpenACC kernels loop annotator parses the loop end test in C/C++ "for" loops to ensure the loop bound can safely be hoisted outside of the loop. The Fortran front end does not have these problems because the normal semantics of DO loops is already to evaluate the loop bound only once.
The problem addressed by the first patch is that the C/C++ front ends sometimes end up reversing the sense of the comparison, so that (for instance) in a comparison involving two local variables, it was mis-identifying the loop variable and loop bound. This is solved by rearranging the code to find the loop variable from the initializer first. The second patch generalizes the test for hoist-ability of the loop bound expression to allow not just constants and loop-invariant local variables, but also most expressions involving only constants and loop-invariant local variables, including calls to functions with constant semantics. We could do a better job of this later in the compilation process when we have dataflow and alias information available, but at present, the compilation of "acc loop" constructs simply assumes that the loop bound is always hoistable even when the "auto" or "seq" clauses are present. So the annotator needs to be conservatively correct rather than rely on such problems being diagnosed later. There is no one available to review patches to the kernels loop annotator at present so I have committed this to the OG10 branch. When this functionality is resubmitted for mainline, a proper review will be required. -Sandra Sandra Loosemore (2): Clean up loop variable extraction in OpenACC kernels loop annotation. Relax some restrictions on the loop bound in kernels loop annotation. gcc/c-family/ChangeLog.omp | 12 + gcc/c-family/c-omp.c | 306 ++++++++++++++------- gcc/testsuite/ChangeLog.omp | 5 + .../goacc/kernels-loop-annotation-21.c | 42 +++ .../goacc/kernels-loop-annotation-22.c | 41 +++ 5 files changed, 304 insertions(+), 102 deletions(-) create mode 100644 gcc/testsuite/c-c++-common/goacc/kernels-loop-annotation-21.c create mode 100644 gcc/testsuite/c-c++-common/goacc/kernels-loop-annotation-22.c -- 2.8.1
