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re PR rtl-optimization/26244 (FAIL: gcc.c-torture/execute/builtin-bitops-1.c execution, -O3 -fomit-frame-pointer -funroll-loops)

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PR rtl-optimization/26244
	* cse.c (fold_rtx): Correctly associate shifts when const_arg1 and/or
	inner_const are negative or greater than or equal to the bitsize of
	MODE.  If SHIFT_COUNT_TRUNCATED is false, the values aren't associated.
	Otherwise, the values are masked using GET_MODE_BITSIZE (mode) - 1.
	Simplify complicated if statement.  For ASHIFT and LSHIFTRT, return
	CONST0_RTX (mode) when the new shift count is greater than or equal to
	to the bitsize of the object being shifted and XEXP (y, 0) has no side
	effects.


Co-Authored-By: Roger Sayle <roger@eyesopen.com>

From-SVN: r115924
This commit is contained in:
John David Anglin 2006-08-04 14:15:37 +00:00 committed by John David Anglin
parent 8443c250af
commit 824a4527c1
2 changed files with 51 additions and 11 deletions
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13
gcc/ChangeLog
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@ -1,3 +1,16 @@
2006-08-04 John David Anglin <dave.anglin@nrc-cnrc.gc.ca>
Roger Sayle <roger@eyesopen.com>
PR rtl-optimization/26244
* cse.c (fold_rtx): Correctly associate shifts when const_arg1 and/or
inner_const are negative or greater than or equal to the bitsize of
MODE. If SHIFT_COUNT_TRUNCATED is false, the values aren't associated.
Otherwise, the values are masked using GET_MODE_BITSIZE (mode) - 1.
Simplify complicated if statement. For ASHIFT and LSHIFTRT, return
CONST0_RTX (mode) when the new shift count is greater than or equal to
to the bitsize of the object being shifted and XEXP (y, 0) has no side
effects.
2006-08-04 Kazu Hirata <kazu@codesourcery.com>
* tree-cfg.c: Fix a comment typo.

49
gcc/cse.c
View File

@ -4267,16 +4267,29 @@ fold_rtx (rtx x, rtx insn)
enum rtx_code associate_code;
rtx new_const;
if (y == 0
|| 0 == (inner_const
= equiv_constant (fold_rtx (XEXP (y, 1), 0)))
|| GET_CODE (inner_const) != CONST_INT
/* If we have compiled a statement like
"if (x == (x & mask1))", and now are looking at
"x & mask2", we will have a case where the first operand
of Y is the same as our first operand. Unless we detect
this case, an infinite loop will result. */
|| XEXP (y, 0) == folded_arg0)
if (is_shift
&& (INTVAL (const_arg1) >= GET_MODE_BITSIZE (mode)
|| INTVAL (const_arg1) < 0))
{
if (SHIFT_COUNT_TRUNCATED)
const_arg1 = GEN_INT (INTVAL (const_arg1)
& (GET_MODE_BITSIZE (mode) - 1));
else
break;
}
if (y == 0)
break;
inner_const = equiv_constant (fold_rtx (XEXP (y, 1), 0));
if (!inner_const || GET_CODE (inner_const) != CONST_INT)
break;
/* If we have compiled a statement like
"if (x == (x & mask1))", and now are looking at
"x & mask2", we will have a case where the first operand
of Y is the same as our first operand. Unless we detect
this case, an infinite loop will result. */
if (XEXP (y, 0) == folded_arg0)
break;
/* Don't associate these operations if they are a PLUS with the
@ -4295,6 +4308,17 @@ fold_rtx (rtx x, rtx insn)
&& exact_log2 (- INTVAL (const_arg1)) >= 0)))
break;
if (is_shift
&& (INTVAL (inner_const) >= GET_MODE_BITSIZE (mode)
|| INTVAL (inner_const) < 0))
{
if (SHIFT_COUNT_TRUNCATED)
inner_const = GEN_INT (INTVAL (inner_const)
& (GET_MODE_BITSIZE (mode) - 1));
else
break;
}
/* Compute the code used to compose the constants. For example,
A-C1-C2 is A-(C1 + C2), so if CODE == MINUS, we want PLUS. */
@ -4312,13 +4336,16 @@ fold_rtx (rtx x, rtx insn)
shift on a machine that does a sign-extend as a pair
of shifts. */
if (is_shift && GET_CODE (new_const) == CONST_INT
if (is_shift
&& GET_CODE (new_const) == CONST_INT
&& INTVAL (new_const) >= GET_MODE_BITSIZE (mode))
{
/* As an exception, we can turn an ASHIFTRT of this
form into a shift of the number of bits - 1. */
if (code == ASHIFTRT)
new_const = GEN_INT (GET_MODE_BITSIZE (mode) - 1);
else if (!side_effects_p (XEXP (y, 0)))
return CONST0_RTX (mode);
else
break;
}