For

---
struct C {
  virtual ~C();
  virtual void f();
};

void
f (C *p)
{
  p->f();
  p->f();
}
---

-mindirect-branch=thunk-extern -O2 on x86-64 GNU/Linux generates:

_Z1fP1C:
.LFB0:
        .cfi_startproc
        pushq   %rbx
        .cfi_def_cfa_offset 16
        .cfi_offset 3, -16
        movq    (%rdi), %rax
        movq    %rdi, %rbx
        jmp     .LIND1
.LIND0:
        pushq   16(%rax)
        jmp     __x86_indirect_thunk
.LIND1:
        call    .LIND0
        movq    (%rbx), %rax
        movq    %rbx, %rdi
        popq    %rbx
        .cfi_def_cfa_offset 8
        movq    16(%rax), %rax
        jmp     __x86_indirect_thunk_rax
        .cfi_endproc

x86-64 is supposed to have asynchronous unwind tables by default, but
there is nothing that reflects the change in the (relative) frame
address after .LIND0.  That region really has to be moved outside of
the .cfi_startproc/.cfi_endproc bracket.

This patch adds TARGET_INDIRECT_BRANCH_REGISTER to force indirect
branch via register whenever -mindirect-branch= is used.  Now,
-mindirect-branch=thunk-extern -O2 on x86-64 GNU/Linux generates:

_Z1fP1C:
.LFB0:
	.cfi_startproc
	pushq	%rbx
	.cfi_def_cfa_offset 16
	.cfi_offset 3, -16
	movq	(%rdi), %rax
	movq	%rdi, %rbx
	movq	16(%rax), %rax
	call	__x86_indirect_thunk_rax
	movq	(%rbx), %rax
	movq	%rbx, %rdi
	popq	%rbx
	.cfi_def_cfa_offset 8
	movq	16(%rax), %rax
	jmp	__x86_indirect_thunk_rax
	.cfi_endproc

so that "-mindirect-branch=thunk-extern" is equivalent to
"-mindirect-branch=thunk-extern -mindirect-branch-register", which is
used by Linux kernel.

gcc/

	PR target/84039
	* config/i386/constraints.md (Bs): Replace
	ix86_indirect_branch_register with
	TARGET_INDIRECT_BRANCH_REGISTER.
	(Bw): Likewise.
	* config/i386/i386.md (indirect_jump): Likewise.
	(tablejump): Likewise.
	(*sibcall_memory): Likewise.
	(*sibcall_value_memory): Likewise.
	Peepholes of indirect call and jump via memory: Likewise.
	(*sibcall_GOT_32): Disallowed for TARGET_INDIRECT_BRANCH_REGISTER.
	(*sibcall_value_GOT_32): Likewise.
	* config/i386/i386.opt: Likewise.
	* config/i386/predicates.md (indirect_branch_operand): Likewise.
	(GOT_memory_operand): Likewise.
	(call_insn_operand): Likewise.
	(sibcall_insn_operand): Likewise.
	(GOT32_symbol_operand): Likewise.
	* config/i386/i386.h (TARGET_INDIRECT_BRANCH_REGISTER): New.

gcc/testsuite/

	PR target/84039
	* gcc.target/i386/indirect-thunk-1.c: Updated.
	* gcc.target/i386/indirect-thunk-2.c: Likewise.
	* gcc.target/i386/indirect-thunk-3.c: Likewise.
	* gcc.target/i386/indirect-thunk-4.c: Likewise.
	* gcc.target/i386/indirect-thunk-5.c: Likewise.
	* gcc.target/i386/indirect-thunk-6.c: Likewise.
	* gcc.target/i386/indirect-thunk-7.c: Likewise.
	* gcc.target/i386/indirect-thunk-attr-1.c: Likewise.
	* gcc.target/i386/indirect-thunk-attr-2.c: Likewise.
	* gcc.target/i386/indirect-thunk-attr-3.c: Likewise.
	* gcc.target/i386/indirect-thunk-attr-4.c: Likewise.
	* gcc.target/i386/indirect-thunk-attr-5.c: Likewise.
	* gcc.target/i386/indirect-thunk-attr-6.c: Likewise.
	* gcc.target/i386/indirect-thunk-attr-7.c: Likewise.
	* gcc.target/i386/indirect-thunk-bnd-1.c: Likewise.
	* gcc.target/i386/indirect-thunk-bnd-2.c: Likewise.
	* gcc.target/i386/indirect-thunk-bnd-3.c: Likewise.
	* gcc.target/i386/indirect-thunk-bnd-4.c: Likewise.
	* gcc.target/i386/indirect-thunk-extern-1.c: Likewise.
	* gcc.target/i386/indirect-thunk-extern-2.c: Likewise.
	* gcc.target/i386/indirect-thunk-extern-3.c: Likewise.
	* gcc.target/i386/indirect-thunk-extern-4.c: Likewise.
	* gcc.target/i386/indirect-thunk-extern-5.c: Likewise.
	* gcc.target/i386/indirect-thunk-extern-6.c: Likewise.
	* gcc.target/i386/indirect-thunk-extern-7.c: Likewise.
	* gcc.target/i386/indirect-thunk-inline-1.c: Likewise.
	* gcc.target/i386/indirect-thunk-inline-2.c: Likewise.
	* gcc.target/i386/indirect-thunk-inline-3.c: Likewise.
	* gcc.target/i386/indirect-thunk-inline-4.c: Likewise.
	* gcc.target/i386/indirect-thunk-inline-5.c: Likewise.
	* gcc.target/i386/indirect-thunk-inline-6.c: Likewise.
	* gcc.target/i386/indirect-thunk-inline-7.c: Likewise.
	* gcc.target/i386/ret-thunk-9.c: Likewise.
	* gcc.target/i386/ret-thunk-10.c: Likewise.
	* gcc.target/i386/ret-thunk-11.c: Likewise.
	* gcc.target/i386/ret-thunk-12.c: Likewise.
	* gcc.target/i386/ret-thunk-13.c: Likewise.
	* gcc.target/i386/ret-thunk-14.c: Likewise.
	* gcc.target/i386/ret-thunk-15.c: Likewise.

From-SVN: r258001