This patch updates assign_parm_find_data_types to assign passed_mode and
nominal_mode with the mode of the built pointer type instead of the
hard-coded Pmode in the case of pass-by-reference. This is in line with
the assignment to passed_mode and nominal_mode in other cases inside the
function.
assign_parm_find_data_types generally uses TYPE_MODE to calculate
passed_mode and nominal_mode:
/* Find mode of arg as it is passed, and mode of arg as it should be
during execution of this function. */
passed_mode = TYPE_MODE (passed_type);
nominal_mode = TYPE_MODE (nominal_type);
this includes the case when the passed argument is a pointer by itself.
However there is a discrepancy when it deals with argument passed by
invisible reference; it builds the argument's corresponding pointer
type, but sets passed_mode and nominal_mode with Pmode directly.
This is OK for targets where Pmode == ptr_mode, but on AArch64 with
ILP32 they are different with Pmode as DImode and ptr_mode as SImode.
When such a reference is passed on stack, the reference is prepared by
the caller in the lower 4 bytes of an 8-byte slot but is fetched by the
callee as an 8-byte datum, of which the higher 4 bytes may contain junk.
It is probably the combination of Pmode != ptr_mode and the particular
ABI specification that make the AArch64 ILP32 the first target on which
the issue manifests itself.
Bootstrapped on x86_64-none-linux-gnu.
OK for the trunk?
Thanks,
Yufeng
gcc/
* function.c (assign_parm_find_data_types): Set passed_mode and
nominal_mode to the TYPE_MODE of nominal_type for the built
pointer type in case of the struct-pass-by-reference.