From: Richard Henderson <richard.henderson@linaro.org>
To: Keith Busch <kbusch@kernel.org>, Eric Blake <eblake@redhat.com>
Cc: "Kevin Wolf" <kwolf@redhat.com>,
"Daniel P. Berrangé" <berrange@redhat.com>,
qemu-block@nongnu.org, qemu-devel@nongnu.org,
"Max Reitz" <mreitz@redhat.com>,
qemu-ppc@nongnu.org, "Gerd Hoffmann" <kraxel@redhat.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Klaus Jensen" <its@irrelevant.dk>,
"Marc-André Lureau" <marcandre.lureau@redhat.com>,
"Philippe Mathieu-Daudé" <philmd@redhat.com>
Subject: Re: [PATCH 07/23] hw/block/nvme: Use definition to avoid dynamic stack allocation
Date: Fri, 7 May 2021 09:22:13 -0700 [thread overview]
Message-ID: <35256418-b002-e6e4-3cff-dcb7d6718d1b@linaro.org> (raw)
In-Reply-To: <20210506021556.GA1187168@dhcp-10-100-145-180.wdc.com>
On 5/5/21 7:15 PM, Keith Busch wrote:
> Thank you, that makes sense. In this case, we are talking about an
> integer constant expression for the value of a 'const' symbol. That
> seems like perfect fodder for a compiler to optimize. I understand it's
> not obligated to do that, but I assumed it would.
It probably did compile the code such that there is no variable-sized
allocation from the stack. That optimization does not change the *semantics*
of the code as written -- the only reason this compiles is via use of a
variable length array.
r~
next prev parent reply other threads:[~2021-05-07 16:23 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-05 21:10 [PATCH 00/23] misc: Remove variable-length arrays on the stack Philippe Mathieu-Daudé
2021-05-05 21:10 ` [PATCH 01/23] block/vpc: Avoid dynamic stack allocation Philippe Mathieu-Daudé
2021-05-05 21:10 ` [PATCH 02/23] chardev/baum: Replace magic values by X_MAX / Y_MAX definitions Philippe Mathieu-Daudé
2021-05-05 21:12 ` Samuel Thibault
2021-05-05 21:24 ` Marc-André Lureau
2021-05-05 21:10 ` [PATCH 03/23] chardev/baum: Use definitions to avoid dynamic stack allocation Philippe Mathieu-Daudé
2021-05-05 21:14 ` Samuel Thibault
2021-05-05 21:27 ` Marc-André Lureau
2021-05-05 21:39 ` Samuel Thibault
2021-05-05 21:10 ` [PATCH 04/23] chardev/baum: Avoid " Philippe Mathieu-Daudé
2021-05-05 21:15 ` Samuel Thibault
2021-05-05 21:29 ` Marc-André Lureau
2021-05-05 21:10 ` [PATCH 05/23] io/channel-websock: Replace strlen(const_str) by sizeof(const_str) - 1 Philippe Mathieu-Daudé
2021-05-06 8:36 ` Daniel P. Berrangé
2021-05-05 21:10 ` [PATCH 06/23] hw/block/dataplane/virtio-blk: Avoid dynamic stack allocation Philippe Mathieu-Daudé
2021-05-06 8:53 ` Stefan Hajnoczi
2021-05-06 9:01 ` Philippe Mathieu-Daudé
2021-05-06 14:47 ` Stefan Hajnoczi
2021-05-06 15:19 ` Philippe Mathieu-Daudé
2021-05-10 9:09 ` Stefan Hajnoczi
2021-05-05 21:10 ` [PATCH 07/23] hw/block/nvme: Use definition to avoid " Philippe Mathieu-Daudé
2021-05-05 21:22 ` Keith Busch
2021-05-05 22:07 ` Philippe Mathieu-Daudé
2021-05-05 23:09 ` Eric Blake
2021-05-06 0:14 ` Warner Losh
2021-05-06 2:15 ` Keith Busch
2021-05-06 6:42 ` Philippe Mathieu-Daudé
2021-05-07 16:22 ` Richard Henderson [this message]
2021-05-06 6:27 ` Klaus Jensen
2021-05-07 15:59 ` Richard Henderson
2021-05-05 21:10 ` [PATCH 08/23] hw/block/nvme: Avoid " Philippe Mathieu-Daudé
2021-05-06 6:43 ` Klaus Jensen
2021-05-05 21:10 ` [PATCH 09/23] hw/net/e1000e_core: Use definition to avoid " Philippe Mathieu-Daudé
2021-05-06 3:35 ` Jason Wang
2021-05-07 16:29 ` Richard Henderson
2021-05-05 21:10 ` [PATCH 10/23] hw/ppc/pnv: Avoid " Philippe Mathieu-Daudé
2021-05-06 2:12 ` David Gibson
2021-05-05 21:10 ` [PATCH 11/23] hw/intc/xics: " Philippe Mathieu-Daudé
2021-05-06 2:13 ` David Gibson
2021-05-06 8:22 ` Greg Kurz
2021-05-06 13:52 ` Philippe Mathieu-Daudé
2021-05-05 21:10 ` [PATCH 12/23] hw/i386/multiboot: " Philippe Mathieu-Daudé
2021-05-07 16:27 ` Richard Henderson
2021-05-05 21:10 ` [PATCH 13/23] hw/usb/hcd-xhci: " Philippe Mathieu-Daudé
2021-05-07 16:34 ` Richard Henderson
2021-05-05 21:10 ` [PATCH 14/23] hw/usb/hcd-ohci: Use definition to avoid " Philippe Mathieu-Daudé
2021-05-07 16:39 ` Richard Henderson
2021-05-05 21:10 ` [PATCH 15/23] net: Avoid " Philippe Mathieu-Daudé
2021-05-06 2:15 ` David Gibson
2021-05-06 7:09 ` Jason Wang
2021-05-05 21:10 ` [PATCH 16/23] ui/curses: " Philippe Mathieu-Daudé
2021-05-07 16:42 ` Richard Henderson
2021-05-05 21:10 ` [PATCH 17/23] ui/spice-display: " Philippe Mathieu-Daudé
2021-05-05 21:10 ` [PATCH 18/23] ui/vnc-enc-hextile: Use definitions to avoid " Philippe Mathieu-Daudé
2021-05-07 16:46 ` Richard Henderson
2021-05-05 21:10 ` [PATCH 19/23] ui/vnc-enc-tight: Avoid " Philippe Mathieu-Daudé
2021-05-05 21:10 ` [PATCH 20/23] util/iov: " Philippe Mathieu-Daudé
2021-05-05 21:10 ` [PATCH 21/23] target/ppc/kvm: " Philippe Mathieu-Daudé
2021-05-05 21:10 ` Philippe Mathieu-Daudé
2021-05-06 2:16 ` David Gibson
2021-05-06 2:16 ` David Gibson
2021-05-05 21:10 ` [PATCH 22/23] tests/unit/test-vmstate: " Philippe Mathieu-Daudé
2021-05-07 16:52 ` Richard Henderson
2021-05-05 21:10 ` [PATCH 23/23] configure: Prohibit variable-length allocations by using -Wvla CPPFLAG Philippe Mathieu-Daudé
2021-05-07 16:56 ` Richard Henderson
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