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From-SVN: r1581
This commit is contained in:
Tom Wood 1992-07-13 12:45:29 +00:00
parent 6f6547765e
commit 3915de9468
1 changed files with 75 additions and 25 deletions
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100
gcc/jump.c
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@ -544,7 +544,7 @@ jump_optimize (f, cross_jump, noop_moves, after_regscan)
rtx reallabelprev;
rtx temp, temp1, temp2, temp3, temp4, temp5;
rtx nlabel;
int this_is_simplejump, this_is_condjump;
int this_is_simplejump, this_is_condjump, reversep;
#if 0
/* If NOT the first iteration, if this is the last jump pass
(just before final), do the special peephole optimizations.
@ -802,12 +802,19 @@ jump_optimize (f, cross_jump, noop_moves, after_regscan)
}
}
/* If we have x = a; if (...) x = b;
and either A or B is zero, or if we have if (...) x = 0;
and jumps are expensive, try to use a store-flag insn to
avoid the jump. (If the jump would be faster, the machine
should not have defined the scc insns!). These cases are often
made by the previous optimization.
/* We deal with four cases:
1) x = a; if (...) x = b; and either A or B is zero,
2) if (...) x = 0; and jumps are expensive,
3) x = a; if (...) x = b; and A and B are constants where all the
set bits in A are also set in B and jumps are expensive, and
4) x = a; if (...) x = b; and A and B non-zero, and jumps are
more expensive.
In each of these try to use a store-flag insn to avoid the jump.
(If the jump would be faster, the machine should not have
defined the scc insns!). These cases are often made by the
previous optimization.
INSN here is the jump around the store. We set:
@ -841,7 +848,7 @@ jump_optimize (f, cross_jump, noop_moves, after_regscan)
)
|| GET_CODE (temp3) == CONST_INT))
/* Make the latter case look like x = x; if (...) x = 0; */
|| ((temp3 = temp1, BRANCH_COST > 1)
|| ((temp3 = temp1, BRANCH_COST >= 2)
&& temp2 == const0_rtx))
/* INSN must either branch to the insn after TEMP or the insn
after TEMP must branch to the same place as INSN. */
@ -851,33 +858,47 @@ jump_optimize (f, cross_jump, noop_moves, after_regscan)
&& JUMP_LABEL (temp4) == JUMP_LABEL (insn)))
&& (temp4 = get_condition (insn, &temp5)) != 0
/* If B is zero, OK; if A is zero, can only do this if we
can reverse the condition. */
&& (temp2 == const0_rtx
/* If B is zero, OK; if A is zero, can only do (1) if we
can reverse the condition. See if (3) applies possibly
by reversing the condition. Prefer reversing to (4) when
branches are very expensive. */
&& ((reversep = 0, temp2 == const0_rtx)
|| (temp3 == const0_rtx
&& (can_reverse_comparison_p (temp4, insn)))))
&& (reversep = can_reverse_comparison_p (temp4, insn)))
|| (BRANCH_COST >= 2
&& GET_CODE (temp2) == CONST_INT
&& GET_CODE (temp3) == CONST_INT
&& ((INTVAL (temp2) & INTVAL (temp3)) == INTVAL (temp2)
|| ((INTVAL (temp2) & INTVAL (temp3)) == INTVAL (temp3)
&& (reversep = can_reverse_comparison_p (temp4,
insn)))))
|| BRANCH_COST >= 3))
{
enum rtx_code code = GET_CODE (temp4);
rtx yes = temp3, var = temp1;
rtx uval, cval, var = temp1;
int normalizep;
rtx target;
/* If necessary, reverse the condition. */
if (temp3 == const0_rtx)
code = reverse_condition (code), yes = temp2;
if (reversep)
code = reverse_condition (code), uval = temp2, cval = temp3;
else
uval = temp3, cval = temp2;
/* See if we can do this with a store-flag insn. */
start_sequence ();
/* If YES is the constant 1, it is best to just compute
the result directly. If YES is constant and STORE_FLAG_VALUE
/* If CVAL is non-zero, normalize to -1. Otherwise,
if UVAL is the constant 1, it is best to just compute
the result directly. If UVAL is constant and STORE_FLAG_VALUE
includes all of its bits, it is best to compute the flag
value unnormalized and `and' it with YES. Otherwise,
normalize to -1 and `and' with YES. */
normalizep = (yes == const1_rtx ? 1
: (GET_CODE (yes) == CONST_INT
&& (INTVAL (yes) & ~ STORE_FLAG_VALUE) == 0) ? 0
: -1);
value unnormalized and `and' it with UVAL. Otherwise,
normalize to -1 and `and' with UVAL. */
normalizep = (cval != const0_rtx ? -1
: (uval == const1_rtx ? 1
: (GET_CODE (uval) == CONST_INT
&& (INTVAL (uval) & ~STORE_FLAG_VALUE) == 0)
? 0 : -1));
/* We will be putting the store-flag insn immediately in
front of the comparison that was originally being done,
@ -899,10 +920,39 @@ jump_optimize (f, cross_jump, noop_moves, after_regscan)
{
rtx seq;
if (normalizep != 1)
target = expand_and (yes, target,
/* Both CVAL and UVAL are non-zero. */
if (cval != const0_rtx && uval != const0_rtx)
{
rtx tem1, tem2;
tem1 = expand_and (uval, target, NULL_RTX);
if (GET_CODE (cval) == CONST_INT
&& GET_CODE (uval) == CONST_INT
&& (INTVAL (cval) & INTVAL (uval)) == INTVAL (cval))
tem2 = cval;
else
{
tem2 = expand_unop (GET_MODE (var), one_cmpl_optab,
target, NULL_RTX, 0);
tem2 = expand_and (cval, tem2, tem2);
}
/* If we usually make new pseudos, do so here. This
turns out to help machines that have conditional
move insns. */
if (flag_expensive_optimizations)
target = 0;
target = expand_binop (GET_MODE (var), ior_optab,
tem1, tem2, target,
1, OPTAB_WIDEN);
}
else if (normalizep != 1)
target = expand_and (uval, target,
(GET_CODE (target) == REG
? target : NULL_RTX));
seq = gen_sequence ();
end_sequence ();
emit_insn_before (seq, temp5);