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Re: [PE-POST] Adjust Bit-region in expand_assignment
- From: Jeff Law <law at redhat dot com>
- To: Bernd Edlinger <bernd dot edlinger at hotmail dot de>, Richard Biener <richard dot guenther at gmail dot com>
- Cc: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>, Jakub Jelinek <jakub at redhat dot com>
- Date: Tue, 03 Dec 2013 22:55:32 -0700
- Subject: Re: [PE-POST] Adjust Bit-region in expand_assignment
- Authentication-results: sourceware.org; auth=none
- References: <DUB122-W396D54115D70C9FF68A8D2E43C0 at phx dot gbl>,<CAFiYyc13uxba37WySOxXf14UVJW15_DM7jggNGbR4H2cK96Eiw at mail dot gmail dot com>,<DUB122-W323D4AAAEA1AFA890BF243E43C0 at phx dot gbl>,<CAFiYyc13wC0jmZ4xELAiL5L5Sbh0yauZWViP2hTdR+H4s0iPSw at mail dot gmail dot com>,<DUB122-W4D571A91831593BA22438E43C0 at phx dot gbl>,<CAFiYyc1ECAdBJTkcziSL_f9SQyYUPY9k19QWqkN+RfLO=i2zaQ at mail dot gmail dot com>,<20130910193228 dot GE6732 at virgil dot suse>,<DUB122-W22DAEEE94B5ED3308F6967E4390 at phx dot gbl>,<CAFiYyc3AHggjJbEmZvC_fh67o+LVpTBRdwyUv8T6EhQFE2vNWQ at mail dot gmail dot com>,<DUB122-W281E996A4885309956418EE4250 at phx dot gbl>,<20130916230945 dot GK6732 at virgil dot suse>,<DUB122-W209385567C3551814F6331E4020 at phx dot gbl>,<DUB122-W44FF2B06EE812E903A9365E4F00 at phx dot gbl> <DUB122-W46DEE578F1C4A1E159AA2FE4D50 at phx dot gbl>
On 12/03/13 06:27, Bernd Edlinger wrote:
This comment is completely out of sync: There is no longer any force_reg in that if-block,
and a constant address in TO_RTX has SImode or DImode in GET_MODE (XEXP (to_rtx, 0))
I do not know how to make it a VOIDmode, therefore the comment does not help either.
I thought that comment looked familiar... That's because it was mine...
The way that was triggered in the past can be found in this ancient posting:
http://gcc.gnu.org/ml/gcc-patches/1999-03n/msg00654.html
The code went through a major revamp in 2002 which removed the force_reg
calls without updating/removing the comment.
Additionally, the way we represent and thus ultimately expand the memory
reference has changed in ways that make it harder, if not impossible to
have a constant address at these points. Even if were to hack up the
expanders to force a constant address rather than a REG it's still
nontrivial to get into that code with a constant address.
I wouldn't be terribly surprised to find all kinds of dead code in the
expanders.
So the comment clearly needs to get zapped.
As for the consistency of bitregion_start/bitregion_end, I'm just not
familiar enough with this code or the issues for the C++ memory model to
comment.
jeff