https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113550
Bug ID: 113550
Summary: data512_t initializers dereference a clobbered
register
Product: gcc
Version: 12.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: ianthompson at microsoft dot com
Target Milestone: ---
Target: aarch64
Created attachment 57189
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=57189&action=edit
Additional non-minimal failing cases
When initializing or copying a data512_t, the compiler is generating code which
clobbers the register containing the source pointer of the copy. Initially
observed on Arm GNU Toolchain 12.2.Rel1, but this also reproduces on trunk.
Minimal reproduction, hits a segfault when compiled with "aarch64-none-elf-gcc
-march=armv9-a+ls64":
#include <arm_acle.h>
void test_data512_init() {
data512_t my_value = {};
}
This code generates this assembly snippet for initializing my_value:
adrp x0, .LC0
add x0, x0, :lo12:.LC0
ldp x0, x1, [x0]
ldp x2, x3, [x0, 16]
ldp x4, x5, [x0, 32]
ldp x6, x7, [x0, 48]
Notice that the first ldp clobbers x0, redirecting the remaining 3 loads to
whatever address happens to be in val[0] of the initializer.
Similar incorrect code is generated in many other situations that involve
copying a data512_t (passing a global variable to a function, dereferencing a
data512_t*, etc). See the attached source file for the other failing cases I'm
seeing.
