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Avoid hard register combinations

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From-SVN: r37704
This commit is contained in:
Bernd Schmidt 2000-11-24 11:28:51 +00:00 committed by Bernd Schmidt
parent 2f401cc807
commit c34102419d
2 changed files with 54 additions and 7 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
2000-11-24 Bernd Schmidt <bernds@redhat.co.uk>
* combine.c (cant_combine_insn_p): New function.
(try_combine): Use it.
2000-11-24 Nathan Sidwell <nathan@codesourcery.com>
* c-parse.in (unary_expr): Move VA_ARG from here ...

56
gcc/combine.c
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@ -366,6 +366,7 @@ static void do_SUBST_INT PARAMS ((unsigned int *,
static void init_reg_last_arrays PARAMS ((void));
static void setup_incoming_promotions PARAMS ((void));
static void set_nonzero_bits_and_sign_copies PARAMS ((rtx, rtx, void *));
static int cant_combine_insn_p PARAMS ((rtx));
static int can_combine_p PARAMS ((rtx, rtx, rtx, rtx, rtx *, rtx *));
static int sets_function_arg_p PARAMS ((rtx));
static int combinable_i3pat PARAMS ((rtx, rtx *, rtx, rtx, int, rtx *));
@ -1455,6 +1456,46 @@ contains_muldiv (x)
}
}
/* Determine whether INSN can be used in a combination. Return nonzero if
not. This is used in try_combine to detect early some cases where we
can't perform combinations. */
static int
cant_combine_insn_p (insn)
rtx insn;
{
rtx set;
rtx src, dest;
/* If this isn't really an insn, we can't do anything.
This can occur when flow deletes an insn that it has merged into an
auto-increment address. */
if (! INSN_P (insn))
return 1;
/* Never combine loads and stores involving hard regs. The register
allocator can usually handle such reg-reg moves by tying. If we allow
the combiner to make substitutions of hard regs, we risk aborting in
reload on machines that have SMALL_REGISTER_CLASSES.
As an exception, we allow combinations involving fixed regs; these are
not available to the register allocator so there's no risk involved. */
set = single_set (insn);
if (! set)
return 0;
src = SET_SRC (set);
dest = SET_DEST (set);
if (REG_P (src)
&& REGNO (src) < FIRST_PSEUDO_REGISTER
&& ! fixed_regs[REGNO (src)])
return 1;
if (REG_P (dest)
&& REGNO (dest) < FIRST_PSEUDO_REGISTER
&& ! fixed_regs[REGNO (dest)])
return 1;
return 0;
}
/* Try to combine the insns I1 and I2 into I3.
Here I1 and I2 appear earlier than I3.
I1 can be zero; then we combine just I2 into I3.
@ -1509,13 +1550,14 @@ try_combine (i3, i2, i1, new_direct_jump_p)
register rtx link;
int i;
/* If any of I1, I2, and I3 isn't really an insn, we can't do anything.
This can occur when flow deletes an insn that it has merged into an
auto-increment address. We also can't do anything if I3 has a
REG_LIBCALL note since we don't want to disrupt the contiguity of a
libcall. */
if (! INSN_P (i3) || ! INSN_P (i2) || (i1 && ! INSN_P (i1))
/* Exit early if one of the insns involved can't be used for
combinations. */
if (cant_combine_insn_p (i3)
|| cant_combine_insn_p (i2)
|| (i1 && cant_combine_insn_p (i1))
/* We also can't do anything if I3 has a
REG_LIBCALL note since we don't want to disrupt the contiguity of a
libcall. */
#if 0
/* ??? This gives worse code, and appears to be unnecessary, since no
pass after flow uses REG_LIBCALL/REG_RETVAL notes. */