On 12/8/22 04:51, Claudiu Zissulescu Ianculescu via Gcc wrote:
Hi Eric,
The problem shows in loop-doloop.c when I introduce a loop end pattern
that replaces the first jump instruction (JUMP_INSN 15) with a pattern
that clobbers CC reg. However, the DF doesn't look like it works as
the doloop step cannot find the CC reg alive. Please see
loop-doloop.c:766. Hence, it introduces the doloop_end patterns, and
renders the compare instruction (INSN 14) dead code. leading to
But simply inserting an instruction that clobbers CC can't be a valid
thing to do. You have to verify that the register isn't live at the
point where you want to do the insertion.
Or is that the core of the problem -- that life analysis is inaccurate
or unavailable?
Jeff
