[Bug other/68618] New: interrupt fails on ICE in some call cases with miamcu with -O2/3

["vaalfreja at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68618

            Bug ID: 68618
           Summary: interrupt fails on ICE in some call cases with miamcu
                    with -O2/3
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vaalfreja at gmail dot com
  Target Milestone: ---

Reproduce:
bash-4.2$ cat ../i2.c
struct interrupt_frame;

void (*foo1[1])(int a, int b);

void foo2(int c)
{
        foo1[c](1,2);
}

static __attribute__((interrupt)) void my_isr(struct interrupt_frame *frame)
{
        int c;
        foo2(c);
}


int main()
{
}
bash-4.2$ ./../gcc_trunk_64bit_old_interrupt/install/bin/gcc -m32 -miamcu -O3
-DU ../i2.c
../i2.c: In function âfoo2â:
../i2.c:8:1: error: unable to find a register to spill
 }
 ^
../i2.c:8:1: error: this is the insn:
(call_insn/j 10 19 11 2 (call (mem:QI (reg/f:SI 91 [90]) [0 *_3 S1 A8])
        (const_int 0 [0])) ../i2.c:7 662 {*sibcall}
     (expr_list:REG_DEAD (reg/f:SI 91 [90])
        (expr_list:REG_DEAD (reg:SI 1 dx)
            (expr_list:REG_DEAD (reg:SI 0 ax)
                (expr_list:REG_CALL_DECL (nil)
                    (nil)))))
    (expr_list:SI (use (reg:SI 0 ax))
        (expr_list:SI (use (reg:SI 1 dx))
            (nil))))
../i2.c:8:1: internal compiler error: in assign_by_spills, at
lra-assigns.c:1431
0xa6f4a8 _fatal_insn(char const*, rtx_def const*, char const*, int, char
const*)
        .././../TRUNK/gcc6/gcc/rtl-error.c:109
0x970019 assign_by_spills
        .././../TRUNK/gcc6/gcc/lra-assigns.c:1431
0x970a53 lra_assign()
        .././../TRUNK/gcc6/gcc/lra-assigns.c:1606
0x96c459 lra(_IO_FILE*)
        .././../TRUNK/gcc6/gcc/lra.c:2344
0x922919 do_reload
        .././../TRUNK/gcc6/gcc/ira.c:5392
0x922919 execute
        .././../TRUNK/gcc6/gcc/ira.c:5563
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <http://gcc.gnu.org/bugs.html> for instructions.

This bug can be fixed with:
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index cb6f8f4..b1523e0 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -5339,8 +5339,8 @@ ix86_set_current_function (tree fndecl)
     reinit_regs ();
   /* AX register is only preserved if there are no caller-saved
      registers.  */
-  else if (cfun->machine->no_caller_saved_registers
-          == call_used_regs[AX_REG])
+  else if ((cfun->machine->no_caller_saved_registers
+          == call_used_regs[AX_REG]) || TARGET_IAMCU)
     reinit_regs ();
 }

However, unconditional calling of reinit_regs is bad.