On Tue, Jan 21, 2025 at 5:45 PM Andrew Pinski <pins...@gmail.com> wrote: > > On Thu, Aug 8, 2024 at 2:07 PM Andrew Pinski <pins...@gmail.com> wrote: > > > > On Fri, Aug 2, 2024 at 7:30 AM Jeff Law <jeffreya...@gmail.com> wrote: > > > > > > > > > > > > On 8/1/24 4:12 AM, Surya Kumari Jangala wrote: > > > > lra: emit caller-save register spills before call insn [PR116028] > > > > > > > > LRA emits insns to save caller-save registers in the > > > > inheritance/splitting pass. In this pass, LRA builds EBBs (Extended > > > > Basic Block) and traverses the insns in the EBBs in reverse order from > > > > the last insn to the first insn. When LRA sees a write to a pseudo (that > > > > has been assigned a caller-save register), and there is a read following > > > > the write, with an intervening call insn between the write and read, > > > > then LRA generates a spill immediately after the write and a restore > > > > immediately before the read. The spill is needed because the call insn > > > > will clobber the caller-save register. > > > > > > > > If there is a write insn and a call insn in two separate BBs but > > > > belonging to the same EBB, the spill insn gets generated in the BB > > > > containing the write insn. If the write insn is in the entry BB, then > > > > the spill insn that is generated in the entry BB prevents shrink wrap > > > > from happening. This is because the spill insn references the stack > > > > pointer and hence the prolog gets generated in the entry BB itself. > > > > > > > > This patch ensures that the spill insn is generated before the call insn > > > > instead of after the write. This is also more efficient as the spill now > > > > occurs only in the path containing the call. > > > > > > > > 2024-08-01 Surya Kumari Jangala <jskum...@linux.ibm.com> > > > > > > > > gcc/ > > > > PR rtl-optimization/PR116028 > > > > * lra-constraints.cc (split_reg): Spill register before call > > > > insn. > > > > (latest_call_insn): New variable. > > > > (inherit_in_ebb): Track the latest call insn. > > > > > > > > gcc/testsuite/ > > > > PR rtl-optimization/PR116028 > > > > * gcc.dg/ira-shrinkwrap-prep-1.c: Remove xfail for powerpc. > > > > * gcc.dg/pr10474.c: Remove xfail for powerpc. > > > Implementation looks fine. I would suggest a comment indicating why > > > we're inserting before last_call_insn. Otherwise someone in the future > > > would have to find the patch submission to know why we're handling that > > > case specially. > > > > > > OK with that additional comment. > > > > This causes bootstrap failure on aarch64-linux-gnu; self-tests fail at > > stage 2. Looks to be wrong code is produced compiling stage 2 > > compiler. > > I have not looked further than that right now. > > I decided to re-apply the patch to the trunk locally and see if I > could debug what was going wrong. The good news is the bootstrap > failure is gone. > The bad news is I don't know why though. I am going to see if I can > bisect where the failure mode I was getting disappears. That should > help decide if the bug has got latent or really fixed.
Just a small update before I go to bed. Here are some information on the revisions which work/don't work (with the patch re-applied): r15-5746-g0547dbb725b6d8 fails the way it was reported above r15-6350-gbb829ce157f8b4 fails with a bootstrap comparison r15-6351-g24df430108c0cd fails with a bootstrap comparison r15-7077-g96f4ba4d19a765 works r15-7116-g3f641a8f1d1fafc0c6531aee185d0e74998987d5 works I will be testing more revisions tomorrow. But it looks like we are down to ~700 revisions. Thanks, Andrew Pinski > > Thanks, > Andrew Pinski > > > > > Thanks, > > Andrew > > > > > > > > Thanks, > > > jeff
