On Tue, Mar 20, 2018 at 7:18 PM, Bin Cheng <bin.ch...@arm.com> wrote: > Hi, > As noted in PR84969, fuse_memset_builtins breaks dependence between different > memsets. > Specifically, it reorders different builtin memset partitions though it > doesn't merge > them in the end. This simple patch fixes this wrong code issue by checking > if any two > builtin memsets set the same rhs value or not. Note we don't need to bother > if two > memsets intersect with each other or not. > > Of course, this would miss opportunity merging S1/S3 in below case: > memset(p+12, 0, 12); //<-----S1 > memset(p+17, 1, 10); > memset(p, 0, 12); //<-----S3 > In my opinion, this should be resolved in a more general way maximizing > parallelism > as well as merging opportunities when sorting partitions into topological > order from > dependence graph, which isn't GCC8 task. > > Bootstrap and test on x86_64 and AArch64 ongoing. Okay if no failures?
OK. Richard. > Thanks, > bin > > 2018-03-20 Bin Cheng <bin.ch...@arm.com> > > PR tree-optimization/84969 > * tree-loop-distribution.c (fuse_memset_builtins): Don't reorder > builtin memset partitions if they set differnt rhs values. > > gcc/testsuite > 2018-03-20 Bin Cheng <bin.ch...@arm.com> > > PR tree-optimization/84969 > * gcc.dg/tree-ssa/pr84969.c: New test. >
