https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103276
Bug ID: 103276
Summary: [openacc] Trying to map already mapped data
Product: gcc
Version: og11 (devel/omp/gcc-11)
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libgomp
Assignee: unassigned at gcc dot gnu.org
Reporter: tetra2005 at gmail dot com
CC: jakub at gcc dot gnu.org
Target Milestone: ---
Created attachment 51811
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51811&action=edit
Reprocase
I've ran into a duplicate mapping error with OpenACC which seems to be caused
by invalid handling of ENTER DATA pragma.
The pragma, when applied to a parameter of derived type, also maps some
spurious local variable to device memory. After the function exits, another one
is called and tries to map it's own local variables which causes aliasing
conflict due to overlapping memory ranges in libgomp splay tree structures:
libgomp: Trying to map into device [0x7fffffffcf80..0x7fffffffcfd8) object
when [0x7fffffffcfc8..0x7fffffffcfd0) is already mapped
The assembly looks like
leaq 8(%rsp), %rax # POINTER TO LOCAL STACK VAR
...
subq $8, %rsp
movl $2, %esi # mapnum
movq %rdi, 24(%rsp) # hostaddrs[0] (OK)
movl $-1, %edi # flags_m
movq %rax, 32(%rsp) # hostaddrs[1] (POINTS TO LOCAL STACK VAR)
xorl %eax, %eax
pushq $0
leaq 32(%rsp), %rdx # hostaddrs
call GOACC_enter_exit_data
Here hostaddrs[1] points to a spurious variable in current stack frame.
Gimple code seems to be correct
voidD.27 copyin_simple (struct simple & restrict varD.3961)
{
struct .omp_data_t.1D.3962 D.3965;
...
# .MEM_4 = VDEF <.MEM_3>
D.3965.varD.3964 = &varD.3961;
but expanded RTL is not:
;; .omp_data_arr.2.var = &var;
(insn 8 7 9 (parallel [
(set (reg:DI 84)
(plus:DI (reg/f:DI 77 virtual-stack-vars)
(const_int -24 [0xffffffffffffffe8])))
(clobber (reg:CC 17 flags))
]) "repro.f90":11:28 -1
(nil))
(insn 9 8 0 (set (mem/f/c:DI (plus:DI (reg/f:DI 77 virtual-stack-vars)
(const_int -8 [0xfffffffffffffff8])) [6 D.3965.varD.3964+0 S8
A64])
(reg:DI 84)) "repro.f90":11:28 -1
(nil))
Reproduced with attached code on devel/omp/gcc-11 branch (commit f85ed2296,
2021 Nov 10) with
gfortran -O2 -ffree-form -ffree-line-length-none -fopenacc
-foffload-options=-march=gfx908 -fdump-tree-all-all -fdump-rtl-all-all -S
repro.f90
