https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96019
Bug ID: 96019
Summary: Optimization forgets non-default scalar_storage_order
Product: gcc
Version: 9.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: arthur200126 at gmail dot com
Target Milestone: ---
Created attachment 48818
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48818&action=edit
test case
The attached code uses a scalar_storage_order to access a byte field in big
endian.
On an x86-64 Windows system, the output without optimization, as expected, is
"aabbccdd 1122". The output with optimization (Og) is "ddccbbaa 2211".
The same happens on the https://gcc.godbolt.org/ site. With O0 a bswap can be
found, but it is gone in -O1 and -Og.
I was unable to find the responsible option by bisection on the godbolt
instance, but that could just be a godbolt thing.
