Currently if requires_stack_frame_p() returns true for some insn, the shrink-wrapping debug output contains only the number of a block containing that insn.
But it is very useful to see the particular insn that requires the prologue. Let's call print_rtl_single to display that insn in the following pass dump. 2020-07-04 Alexander Popov <alex.po...@linux.com> gcc/ChangeLog: * shrink-wrap.c (try_shrink_wrapping): Improve debug output. N.B. This is my first GCC patch, I don't have write access for the project. --- gcc/shrink-wrap.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/gcc/shrink-wrap.c b/gcc/shrink-wrap.c index 775db9ce888..d70635e94a3 100644 --- a/gcc/shrink-wrap.c +++ b/gcc/shrink-wrap.c @@ -43,6 +43,7 @@ along with GCC; see the file COPYING3. If not see #include "rtl-iter.h" #include "valtrack.h" #include "function-abi.h" +#include "print-rtl.h" /* Return true if INSN requires the stack frame to be set up. PROLOGUE_USED contains the hard registers used in the function @@ -735,7 +736,11 @@ try_shrink_wrapping (edge *entry_edge, rtx_insn *prologue_seq) set_up_by_prologue.set)) { if (dump_file) - fprintf (dump_file, "Block %d needs the prologue.\n", bb->index); + { + fprintf (dump_file, "Block %d needs prologue due to insn %d:\n", + bb->index, INSN_UID (insn)); + print_rtl_single (dump_file, insn); + } pro = nearest_common_dominator (CDI_DOMINATORS, pro, bb); break; } -- 2.25.4