[Bug target/81313] New: Bad stack realignment code with -mno-accumulate-outgoing-args

[hjl.tools at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81313

            Bug ID: 81313
           Summary: Bad stack realignment code with
                    -mno-accumulate-outgoing-args
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hjl.tools at gmail dot com
                CC: pavel.v.chupin at gmail dot com
  Target Milestone: ---

[hjl@gnu-tools-1 gcc]$ cat /tmp/b.c
extern void foo (void);

void
bar (void)
{
  foo ();
}
[hjl@gnu-tools-1 gcc]$ ./xgcc -B./  /tmp/b.c -S -O2
-fno-asynchronous-unwind-tables -mincoming-stack-boundary=3 
-mno-accumulate-outgoing-args  
[hjl@gnu-tools-1 gcc]$ cat b.s
        .file   "b.c"
        .text
        .p2align 4,,15
        .globl  bar
        .type   bar, @function
bar:
        leaq    8(%rsp), %r10
        andq    $-16, %rsp
        pushq   -8(%r10)
        pushq   %rbp
        movq    %rsp, %rbp
        pushq   %r10
        subq    $8, %rsp
        call    foo
        addq    $8, %rsp
        popq    %r10
        popq    %rbp
        leaq    -8(%r10), %rsp
        ret
        .size   bar, .-bar
        .ident  "GCC: (GNU) 7.1.1 20170704"
        .section        .note.GNU-stack,"",@progbits
[hjl@gnu-tools-1 gcc]$ ./xgcc -B./  /tmp/b.c -S -O2
-fno-asynchronous-unwind-tables -mincoming-stack-boundary=3 
-maccumulate-outgoing-args  
[hjl@gnu-tools-1 gcc]$ cat b.s
        .file   "b.c"
        .text
        .p2align 4,,15
        .globl  bar
        .type   bar, @function
bar:
        pushq   %rbp
        movq    %rsp, %rbp
        andq    $-16, %rsp
        call    foo
        leave
        ret
        .size   bar, .-bar
        .ident  "GCC: (GNU) 7.1.1 20170704"
        .section        .note.GNU-stack,"",@progbits
[hjl@gnu-tools-1 gcc]$ 

This is due to

static rtx
ix86_get_drap_rtx (void)
{
  if (ix86_force_drap || !ACCUMULATE_OUTGOING_ARGS)
    crtl->need_drap = true; 

Since nothing is passed on stack, need_trap should be false.