[Bug target/89746] New: powerpc-none-eabi-gcc emits code using stfiwx to misaligned address

[davem at devkitpro dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89746

            Bug ID: 89746
           Summary: powerpc-none-eabi-gcc emits code using stfiwx to
                    misaligned address
           Product: gcc
           Version: 8.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: davem at devkitpro dot org
  Target Milestone: ---

The following code produces an alignment exception on powerpc 750 and I presume
on other powerpc ISAs where unaligned floating point is not allowed.


typedef struct
{
        int i;
        short x, y, z;
} foo;

void bar(foo *p, float f)
{
        int d = f;
        p->y = d>>16;
        p->z = d&0xFFFF;
}

file    "stfiwx-test.c"
        .section        ".text"
        .align 2
        .globl bar
        .type   bar, @function
bar:
.LFB0:
        .cfi_startproc
        fctiwz %f1,%f1
        addi %r3,%r3,6
        stfiwx %f1,0,%r3
        blr
        .cfi_endproc
.LFE0:
        .size   bar, .-bar

compiling with -mstrict-align generates working code

.file   "stfiwx-test.c"
        .section        ".text"
        .align 2
        .globl bar
        .type   bar, @function
bar:
.LFB0:
        .cfi_startproc
        stwu %r1,-16(%r1)
        .cfi_def_cfa_offset 16
        fctiwz %f1,%f1
        addi %r9,%r1,8
        stfiwx %f1,0,%r9
        lwz %r9,8(%r1)
        srawi %r10,%r9,16
        sth %r9,8(%r3)
        sth %r10,6(%r3)
        addi %r1,%r1,16
        .cfi_def_cfa_offset 0
        blr
        .cfi_endproc
.LFE0:
        .size   bar, .-bar