https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80218
--- Comment #4 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> --- Author: rsandifo Date: Fri Mar 31 11:51:32 2017 New Revision: 246614 URL: https://gcc.gnu.org/viewcvs?rev=246614&root=gcc&view=rev Log: PR80218: Call CDCE fails to update the block profile tree-call-cdce.c was updating the edge probabilities and counts but it wasn't updating the corresponding block information. Among other things, this tricked the register allocator into thinking that the libm call was relatively hot and that it wasn't worth assigning call-clobbered registers to values that were live across the call. With correct frequency information, the RA instead keeps x in the first argument register and spills it only around the call. Although the problem has been around for a long time, it became more acute (and would only trigger for the first function in the testcase) after r230488. Until that patch, the code was specific to calls that had no lhs, but that we still had to keep for their effect on errno. After the patch we also used the code for calls with an lhs, provided that the hardware could calculate the lhs directly. gcc/ PR tree-optimization/80218 * tree-call-cdce.c (shrink_wrap_one_built_in_call_with_conds): Update block frequencies and counts. gcc/testsuite/ PR tree-optimization/80218 * gcc.dg/pr80218.c: New test. Added: branches/gcc-6-branch/gcc/testsuite/gcc.dg/pr80218.c Modified: branches/gcc-6-branch/gcc/ChangeLog branches/gcc-6-branch/gcc/testsuite/ChangeLog branches/gcc-6-branch/gcc/tree-call-cdce.c
