https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90032
Bug ID: 90032
Summary: [MSP430] reload uses wrong stack slot for variable
after setjmp/longjmp
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: jozefl.gcc at gmail dot com
Target Milestone: ---
Created attachment 46118
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=46118&action=edit
tester.i
gcc.dg/torture/stackalign/setjmp-1.c fails at execution for msp430-elf at -O1.
An RTL optimization added in r255136 exposed the failure, but if I make this
optimization in the source of the test, then versions of GCC before this also
fail, back to GCC 7. It passes with gcc-6.4, but again that is just because the
RTL at reload is different.
I've attached a reduced testcase (tester.i) based on setjmp-1.c.
> msp430-elf-gcc -O1 -msim tester.i
The failure occurs because the wrong stack slot is used as the first argument
to strcmp.
R1 is the stack pointer, R12 stores the first argument to functions.
> MOV.W R12, 20(R1) ; The address of the string is stored in 20(R1)
> MOV.W #25972, @R12 ; "te"
> MOV.W #29811, 2(R12) ; "st"
> .... (No other modifications of R1)
> .... preparing jmp_buf
> CALL #sub2
> .... Label for return from longjmp
> MOV.W @R1, R12 ; The address of the string is actually in 20(R1)
> CALL #strcmp
Whether the test fails or not seems gated on if frame_pointer_needed == true
for main(). When there is "more" RTL code (i.e. before the revisions that added
the problematic optimizations), then frame_pointer_needed == true so the
address of the "test" string will be used as an offset from the frame pointer,
instead of the stack pointer.
TARGET_FRAME_POINTER_REQUIRED () always returns false for msp430, but if I make
it return true if
(cfun->has_nonlocal_label || cfun->calls_setjmp)
then the test passes and the following code is generated.
The frame pointer is R4, but it is not fixed.
> MOV.W R12, -2(R4)
> MOV.W #25972, @R12
> MOV.W #29811, 2(R12)
> .... (No other modifications of R4)
> CALL #sub2
> .... Label for return from longjmp
> MOV.W -2(R4), R12 ; -2(R4) contains the correct address of "test"
I've attached the assembly file, IRA and reload dumps for tester.i when
compiled with current trunk.
