[Bug rtl-optimization/65912] New: x_rtl.x_frame_offset not updated after frame related insn deleted

["jiwang at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65912

            Bug ID: 65912
           Summary: x_rtl.x_frame_offset not updated after frame related
                    insn deleted
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jiwang at gcc dot gnu.org
  Target Milestone: ---

given the following simple test.c

typedef unsigned long int uint64_t;
typedef __Uint8x8_t uint8x8_t;

typedef struct uint8x8x4_t
{
  uint8x8_t val[4];
} uint8x8x4_t;

__inline uint8x8_t
bar (uint64_t __a)
{
  return (uint8x8_t) __a;
}

uint8x8x4_t foo(uint8x8x4_t v1, uint8x8x4_t v2)
{
  return (uint8x8x4_t){{bar(0), bar(0), bar(0), bar(0)}};
}

on aarch64, compile it with "./cc1-aarch64 -std=c99 -Wall -O3
-ftree-vectorizer-verbose=3"

foo:
        movi    v0.2s, 0
        sub     sp, sp, #128  <== useless stack adjustment
        add     sp, sp, 128   <== useless stack adjustment
        ...

There are useless stack adjustment. A quick investigation shows it's caued by
we first decide to put the return value on stack, then later optimized them
into registers, and all those store to stack are deleted by dse1, but stack
space required kept in x_rtl->x_frame_offset is not updated accordingly.

Although I run into this issue on AArch64, I highly suspect it's a generic
issue when the type of return value is very complex.

Has anyone run into this issue on other architecture like MIPS, PPC?