https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99802
Bug ID: 99802
Summary: [11 regression] Assignment of aggregate done
component-by-component
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: ada
Assignee: unassigned at gcc dot gnu.org
Reporter: simon at pushface dot org
Target Milestone: ---
Created attachment 50481
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=50481&action=edit
Demonstrator, with output assembler
In arm-eabi-gcc version 11.0.1 20210303 (experimental) (GCC),
assigning an aggregate to a memory-mapped register is performed by
assigning the components of the aggregate one-by-one to the register
rather than as a whole word.
The same bug is present in the x86_64-apple-darwin compiler.
In compiler releases up to & including 10, this was done using a
whole-word assignment.
with ATSAM3X8E; use ATSAM3X8E;
with ATSAM3X8E.PMC; use ATSAM3X8E.PMC;
procedure Clock is
begin
PMC_Periph.CKGR_MOR :=
(KEY => 16#37#,
MOSCXTEN => 1, -- main crystal oscillator enable
MOSCRCEN => 1, -- main on-chip rc osc. enable
MOSCXTST => 8, -- startup time
others => <>);
end Clock;
The register is a component of a record:
type PMC_Peripheral is record
...
CKGR_MOR : aliased CKGR_MOR_Register;
pragma Volatile_Full_Access (CKGR_MOR);
...
end record
with Volatile;
with object as so:
PMC_Periph : aliased PMC_Peripheral
with Import, Address => PMC_Base;
and the write respects the Volatile_Full_Access *as it writes each
component separately to the register*! This fails, in this case,
because the PMC hardware requires each write to this register to be
accompanied by a valid value of the KEY field.
The attached aggregate_assignment.zip contains Ada source, and the
10.1.0 and 11.0.1 versions of the arm-eabi cortex-m3 assembler output
by -S.
I've tried compiling the source in aggregate_assignment.zip with the
x86_64-apple-darwin compiler, and the same bug seems to be present.
NOTE, this bug is also present in GNAT CE 2020.
