[Bug other/67648] New: No need to save callee-saved registers in interrupt handler

[hjl.tools at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67648

            Bug ID: 67648
           Summary: No need to save callee-saved registers in interrupt
                    handler
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hjl.tools at gmail dot com
                CC: julia.koval at intel dot com
            Blocks: 67552
  Target Milestone: ---

[hjl@gnu-6 interrupt-1]$ cat call-1.i
extern void bar (void);

void
 __attribute__ ((interrupt))
foo (void)
{
  bar ();
}
[hjl@gnu-6 interrupt-1]$ make call-1.s
/export/build/gnu/gcc/build-x86_64-linux/gcc/xgcc
-B/export/build/gnu/gcc/build-x86_64-linux/gcc/ -O2 -S -o call-1.s call-1.i
[hjl@gnu-6 interrupt-1]$ cat call-1.s
        .file   "call-1.i"
        .section        .text.unlikely,"ax",@progbits
.LCOLDB0:
        .text
.LHOTB0:
        .p2align 4,,15
        .globl  foo
        .type   foo, @function
foo:
.LFB0:
        .cfi_startproc
        pushq   %r15
        .cfi_def_cfa_offset 16
        .cfi_offset 15, -16
        pushq   %r14
        .cfi_def_cfa_offset 24
        .cfi_offset 14, -24
        pushq   %r13
        .cfi_def_cfa_offset 32
        .cfi_offset 13, -32
        pushq   %r12
        .cfi_def_cfa_offset 40
        .cfi_offset 12, -40
        pushq   %r11
        .cfi_def_cfa_offset 48
        .cfi_offset 11, -48
        pushq   %r10
        .cfi_def_cfa_offset 56
        .cfi_offset 10, -56
        pushq   %r9
        .cfi_def_cfa_offset 64
        .cfi_offset 9, -64
        pushq   %r8
        .cfi_def_cfa_offset 72
        .cfi_offset 8, -72
        pushq   %rbp
        .cfi_def_cfa_offset 80
        .cfi_offset 6, -80
        pushq   %rdi
        .cfi_def_cfa_offset 88
        .cfi_offset 5, -88
        pushq   %rsi
        .cfi_def_cfa_offset 96
        .cfi_offset 4, -96
        pushq   %rbx
        .cfi_def_cfa_offset 104
        .cfi_offset 3, -104
        pushq   %rcx
        .cfi_def_cfa_offset 112
        .cfi_offset 2, -112
        pushq   %rdx
        .cfi_def_cfa_offset 120
        .cfi_offset 1, -120
        pushq   %rax
        .cfi_def_cfa_offset 128
        .cfi_offset 0, -128
        subq    $256, %rsp
        .cfi_def_cfa_offset 384
        movups  %xmm0, (%rsp)
        movups  %xmm1, 16(%rsp)
        movups  %xmm2, 32(%rsp)
        movups  %xmm3, 48(%rsp)
        movups  %xmm4, 64(%rsp)
        movups  %xmm5, 80(%rsp)
        movups  %xmm6, 96(%rsp)
        movups  %xmm7, 112(%rsp)
        movups  %xmm8, 128(%rsp)
        movups  %xmm9, 144(%rsp)
        movups  %xmm10, 160(%rsp)
        movups  %xmm11, 176(%rsp)
        movups  %xmm12, 192(%rsp)
        movups  %xmm13, 208(%rsp)
        movups  %xmm14, 224(%rsp)
        movups  %xmm15, 240(%rsp)
        .cfi_offset 17, -384
        .cfi_offset 18, -368
        .cfi_offset 19, -352
        .cfi_offset 20, -336
        .cfi_offset 21, -320
        .cfi_offset 22, -304
        .cfi_offset 23, -288
        .cfi_offset 24, -272
        .cfi_offset 25, -256
        .cfi_offset 26, -240
        .cfi_offset 27, -224
        .cfi_offset 28, -208
        .cfi_offset 29, -192
        .cfi_offset 30, -176
        .cfi_offset 31, -160
        .cfi_offset 32, -144
        call    bar
        movups  (%rsp), %xmm0
        movups  16(%rsp), %xmm1
        movups  32(%rsp), %xmm2
        movups  48(%rsp), %xmm3
        movups  64(%rsp), %xmm4
        movups  80(%rsp), %xmm5
        movups  96(%rsp), %xmm6
        movups  112(%rsp), %xmm7
        movups  128(%rsp), %xmm8
        movups  144(%rsp), %xmm9
        movups  160(%rsp), %xmm10
        movups  176(%rsp), %xmm11
        movups  192(%rsp), %xmm12
        movups  208(%rsp), %xmm13
        movups  224(%rsp), %xmm14
        movups  240(%rsp), %xmm15
        addq    $256, %rsp
        .cfi_restore 32
        .cfi_restore 31
        .cfi_restore 30
        .cfi_restore 29
        .cfi_restore 28
        .cfi_restore 27
        .cfi_restore 26
        .cfi_restore 25
        .cfi_restore 24
        .cfi_restore 23
        .cfi_restore 22
        .cfi_restore 21
        .cfi_restore 20
        .cfi_restore 19
        .cfi_restore 18
        .cfi_restore 17
        .cfi_def_cfa_offset 128
        popq    %rax
        .cfi_def_cfa_offset 120
        popq    %rdx
        .cfi_def_cfa_offset 112
        popq    %rcx
        .cfi_def_cfa_offset 104
        popq    %rbx
        .cfi_def_cfa_offset 96
        popq    %rsi
        .cfi_def_cfa_offset 88
        popq    %rdi
        .cfi_def_cfa_offset 80
        popq    %rbp
        .cfi_def_cfa_offset 72
        popq    %r8
        .cfi_def_cfa_offset 64
        popq    %r9
        .cfi_def_cfa_offset 56
        popq    %r10
        .cfi_def_cfa_offset 48
        popq    %r11
        .cfi_def_cfa_offset 40
        popq    %r12
        .cfi_def_cfa_offset 32
        popq    %r13
        .cfi_def_cfa_offset 24
        popq    %r14
        .cfi_def_cfa_offset 16
        popq    %r15
        .cfi_def_cfa_offset 8
        iret
        .cfi_endproc
.LFE0:
        .size   foo, .-foo
        .section        .text.unlikely
.LCOLDE0:
        .text
.LHOTE0:
        .ident  "GCC: (GNU) 6.0.0 20150917 (experimental)"
        .section        .note.GNU-stack,"",@progbits
[hjl@gnu-6 interrupt-1]$ 

Since RBX and R12-R15 registers are callee-saved, we don't need
to save and restore them in interrupt handler unless they are
modified.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67552
[Bug 67552] [meta] x86 interrupt attribute