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[combine] Only restrict pure simplification in mult-extend subst case, allow other substitutions

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* combine.c (subst): Do not return clobber of zero in widening mult
	case.  Just return x unchanged if it is a no-op substitution.

From-SVN: r230946
This commit is contained in:
Kyrylo Tkachov 2015-11-26 13:07:29 +00:00 • committed by Kyrylo Tkachov
parent 5564c379b0
commit f0e8751330
2 changed files with 10 additions and 8 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
2015-11-26 Kyrylo Tkachov <kyrylo.tkachov@arm.com>
* combine.c (subst): Do not return clobber of zero in widening mult
case. Just return x unchanged if it is a no-op substitution.
2015-11-26 Vladimir Makarov <vmakarov@redhat.com>
PR target/68416

13
gcc/combine.c
View file

@ -5285,7 +5285,7 @@ subst (rtx x, rtx from, rtx to, int in_dest, int in_cond, int unique_copy)
|| GET_CODE (SET_DEST (x)) == PC))
fmt = "ie";
/* Substituting into the operands of a widening MULT is not likely
/* Trying to simplify the operands of a widening MULT is not likely
to create RTL matching a machine insn. */
if (code == MULT
&& (GET_CODE (XEXP (x, 0)) == ZERO_EXTEND
@ -5293,13 +5293,10 @@ subst (rtx x, rtx from, rtx to, int in_dest, int in_cond, int unique_copy)
&& (GET_CODE (XEXP (x, 1)) == ZERO_EXTEND
|| GET_CODE (XEXP (x, 1)) == SIGN_EXTEND)
&& REG_P (XEXP (XEXP (x, 0), 0))
&& REG_P (XEXP (XEXP (x, 1), 0)))
{
if (from == to)
return x;
else
return gen_rtx_CLOBBER (GET_MODE (x), const0_rtx);
}
&& REG_P (XEXP (XEXP (x, 1), 0))
&& from == to)
return x;
/* Get the mode of operand 0 in case X is now a SIGN_EXTEND of a
constant. */