Saga of m68k PIC continues

[Andreas Schwab]

Richard Henderson <rth@redhat.com> writes:

|> On Wed, Dec 11, 2002 at 07:11:05PM -0500, Peter Barada wrote:
|> > +	case 7:
|> > +	  fputs ("@GOTOFF", file);
|> > +	  break;
|> 
|> Note that m68k doesn't have @GOTOFF.  The equivalent there
|> is pc-relative addressing modes.
|> 
|> Ideally, m68k pic code generation would use @GOTPC, a-la
|> 
|> 	extern int foo;
|> 	foo = 1;
|> 
|> 	movel	(%pc, foo@GOTPC), %a0
|> 	moveql	#1, (%a0)
|> 
|> 	static int bar, baz;
|> 	bar = baz;
|> 
|> 	lea	(%pc, bar), %a0
|> 	movel	(%pc, baz), (%a0)
|> 
|> I can't really think of any reason that 68020+ would
|> actually need a pic register.

For -fPIC there is probably no difference, but full 32-bit pc-relative is
still less efficient than register+16 bit offset, so with -fpic the use of
the pic register is usually faster.  Note also that pc-relative addresses
cannot be used as destination operand.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
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