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middle-end: Remove truly_noop_truncation check from convert.c

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This patch eliminates a check of targetm.truly_noop_truncation from
the early middle-end, where the gimple/generic being generated by
GCC's front-ends is being inappropriately influenced by the target's
TRULY_NOOP_TRUNCATION.  The (recent) intention of TRULY_NOOP_TRUNCATION
is to indicate that a backend requires explicit truncation instructions
rather than using SUBREGs to perform truncations.  A long standing
(and probably unintentional) side-effect has been that this setting
also controls whether the middle-end narrows integer operations at
the tree-level.  Understandably, GCC and its testsuite assume that
GIMPLE and GENERIC behave consistently across platforms, and alas
defining TRULY_NOOP_TRUNCATION away from the default triggers several
regressions (including gcc.dg/fold-rotate-1.c).

2020-07-13  Roger Sayle  <roger@nextmovesoftware.com>

gcc/ChangeLog
	* convert.c (convert_to_integer_1): Narrow integer operations
	even on targets that require explicit truncation instructions.
This commit is contained in:
Roger Sayle 2020-07-13 09:49:34 +01:00
parent 9a2ae08b02
commit b8697d0cd0
1 changed files with 4 additions and 10 deletions
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14
gcc/convert.c
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@ -836,16 +836,10 @@ convert_to_integer_1 (tree type, tree expr, bool dofold)
&& POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (arg1, 0))))
break;
if (outprec >= BITS_PER_WORD
|| targetm.truly_noop_truncation (outprec, inprec)
|| inprec > TYPE_PRECISION (TREE_TYPE (arg0))
|| inprec > TYPE_PRECISION (TREE_TYPE (arg1)))
{
tree tem = do_narrow (loc, ex_form, type, arg0, arg1,
expr, inprec, outprec, dofold);
if (tem)
return tem;
}
tree tem = do_narrow (loc, ex_form, type, arg0, arg1,
expr, inprec, outprec, dofold);
if (tem)
return tem;
}
break;