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Re: [PATCH 8/9] Add TARGET_ADDR_SPACE_ZERO_ADDRESS_VALID
- From: Richard Henderson <rth at redhat dot com>
- To: Richard Biener <richard dot guenther at gmail dot com>
- Cc: Jeff Law <law at redhat dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Thu, 15 Oct 2015 08:20:39 +1100
- Subject: Re: [PATCH 8/9] Add TARGET_ADDR_SPACE_ZERO_ADDRESS_VALID
- Authentication-results: sourceware.org; auth=none
- References: <1444280375-20866-1-git-send-email-rth at redhat dot com> <1444280375-20866-9-git-send-email-rth at redhat dot com> <CAFiYyc2fi-0WLEm4ruH1tPn8prORbW-SUd3h2iqfrqiZg9imbw at mail dot gmail dot com> <5616DBBE dot 9080309 at redhat dot com> <CAFiYyc1xeSmHopajQm69ZJX9TjZizvB15RzAxGYhovnSykm1dA at mail dot gmail dot com> <561C41DD dot 5000505 at redhat dot com> <CAFiYyc1tafTBDTP=3meL2Yrbc+eM+n93uBG3ku1_axXGVRXkvQ at mail dot gmail dot com> <561D27EE dot 8030608 at redhat dot com> <561D7095 dot 8080401 at redhat dot com> <CAFiYyc3qgmofZPxE8a71oWhPJEBf1xESinGSA_w5K2Kw8X+xGg at mail dot gmail dot com> <CAFiYyc1B+hKh-+WQ0zMQ8MepErTirXZgm-n1eJkWmGuiVXGCFQ at mail dot gmail dot com>
On 10/14/2015 08:22 PM, Richard Biener wrote:
I think you could trigger bogus CSE of dereferences of literal addresses
from different address-spaces.
Good catch. You're spot on with that.
r~
int test(void)
{
int __seg_fs *f = (int __seg_fs *)16;
int __seg_gs *g = (int __seg_gs *)16;
return *f + *g;
}
test:
movl %fs:16, %eax
addl %eax, %eax
ret