[Bug inline-asm/11563] New: ia64 gcc won't save b0 when inline asm clobbers it

[rcbilson at plg dot uwaterloo dot ca]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11563

           Summary: ia64 gcc won't save b0 when inline asm clobbers it
           Product: gcc
           Version: 3.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: inline-asm
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rcbilson at plg dot uwaterloo dot ca
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: ia64-linux
  GCC host triplet: ia64-linux
GCC target triplet: ia64-linux

Consider the following program:

void f() {}

void
g()
{
	asm( "br.call.sptk b0 = f" : : : "b0" );
}

When compiled with gcc -S, the function g is output as follows:

	.global g#
	.proc g#
g:
	.prologue 2, 2
	.vframe r2
	mov r2 = r12
	.body
#APP
	br.call.sptk b0 = f
#NO_APP
	;;
	.restore sp
	mov r12 = r2
	br.ret.sptk.many b0
	;;
	.endp g#
	.ident	"GCC: (GNU) 3.3.1 20030626 (Debian prerelease)"

As was stated in the "clobbers" section of the asm, the br.call.sptk instruction
overwrites b0.  However, the generated code makes no attempt to save b0 before
the asm; after returning from f, it uses the clobbered value as the address to
return to via br.ret.

If the function g is modified to make an ordinary C function call the problem
goes away, as gcc does properly save and restore b0 around C function calls.