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arm: correctly handle negating INT_MIN in arm_split_atomic_op [PR97534]

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arm_split_atomic_op handles subtracting a constant by converting it
into addition of the negated constant.  But if the type of the operand
is int and the constant is -1 we currently end up generating invalid
RTL which can lead to an abort later on.

The problem is that in a HOST_WIDE_INT, INT_MIN is represented as
0xffffffff80000000 and the negation of this is 0x0000000080000000, but
that's not a valid constant for use in SImode operations.

The fix is straight-forward which is to use gen_int_mode rather than
simply GEN_INT.  This knows how to correctly sign-extend the negated
constant when this is needed.

gcc/
	PR target/97534
	* config/arm/arm.c (arm_split_atomic_op): Use gen_int_mode when
	negating a const_int.
gcc/testsuite
	* gcc.dg/pr97534.c: New test.
This commit is contained in:
Richard Earnshaw 2020-11-24 16:21:17 +00:00
parent 13f93cf533
commit f30a9a8d9e
2 changed files with 10 additions and 1 deletions
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2
gcc/config/arm/arm.c
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@ -30824,7 +30824,7 @@ arm_split_atomic_op (enum rtx_code code, rtx old_out, rtx new_out, rtx mem,
case MINUS:
if (CONST_INT_P (value))
{
value = GEN_INT (-INTVAL (value));
value = gen_int_mode (-INTVAL (value), wmode);
code = PLUS;
}
/* FALLTHRU */

9
gcc/testsuite/gcc.dg/pr97534.c Normal file
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@ -0,0 +1,9 @@
/* PR target/97534 - ICE in decompose on arm*-*-*. */
/* { dg-do compile } */
/* { dg-options "-std=c11 -O2 -g" } */
int f (int a)
{
int b;
__atomic_fetch_sub(&b, (int)(-__INT_MAX__ - 1), (int)0);
}