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Fix two ubsan failures (PR85164)

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Two fixes for UB when handling very large offsets.  The calculation in
force_int_to_mode would have been correct if signed integers used modulo
arithmetic, so just switch to unsigned types.  The calculation in
rtx_addr_can_trap_p_1 didn't handle overflow properly, so switch to
known_subrange_p instead (which is supposed to handle all cases).

2019-04-18  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	PR middle-end/85164
	* combine.c (force_int_to_mode): Cast the argument rather than
	the result of known_alignment.
	* rtlanal.c (rtx_addr_can_trap_p_1): Use known_subrange_p.

gcc/testsuite/
	PR middle-end/85164
	* gcc.dg/pr85164-1.c, gcc.dg/pr85164-2.c: New tests.

From-SVN: r270442
This commit is contained in:
Richard Sandiford 2019-04-18 12:29:56 +00:00 • committed by Richard Sandiford
parent e62817edae
commit cd7f7c54a4
6 changed files with 25 additions and 2 deletions
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7
gcc/ChangeLog
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@ -1,3 +1,10 @@
2019-04-18 Richard Sandiford <richard.sandiford@arm.com>
PR middle-end/85164
* combine.c (force_int_to_mode): Cast the argument rather than
the result of known_alignment.
* rtlanal.c (rtx_addr_can_trap_p_1): Use known_subrange_p.
2019-04-18 Richard Biener <rguenther@suse.de>
PR debug/90131

2
gcc/combine.c
View file

@ -8946,7 +8946,7 @@ force_int_to_mode (rtx x, scalar_int_mode mode, scalar_int_mode xmode,
/* If X is (minus C Y) where C's least set bit is larger than any bit
in the mask, then we may replace with (neg Y). */
if (poly_int_rtx_p (XEXP (x, 0), &const_op0)
&& (unsigned HOST_WIDE_INT) known_alignment (const_op0) > mask)
&& known_alignment (poly_uint64 (const_op0)) > mask)
{
x = simplify_gen_unary (NEG, xmode, XEXP (x, 1), xmode);
return force_to_mode (x, mode, mask, next_select);

2
gcc/rtlanal.c
View file

@ -521,7 +521,7 @@ rtx_addr_can_trap_p_1 (const_rtx x, poly_int64 offset, poly_int64 size,
return (!known_size_p (decl_size) || known_eq (decl_size, 0)
? maybe_ne (offset, 0)
: maybe_gt (offset + size, decl_size));
: !known_subrange_p (offset, size, 0, decl_size));
}
return 0;

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2019-04-18 Richard Sandiford <richard.sandiford@arm.com>
PR middle-end/85164
* gcc.dg/pr85164-1.c, gcc.dg/pr85164-2.c: New tests.
2019-04-18 Richard Biener <rguenther@suse.de>
PR debug/90131

7
gcc/testsuite/gcc.dg/pr85164-1.c Normal file
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@ -0,0 +1,7 @@
/* { dg-options "-O2 -w" } */
a[];
b;
c() {
unsigned long d;
b = a[d - 1 >> 3];
}

4
gcc/testsuite/gcc.dg/pr85164-2.c Normal file
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@ -0,0 +1,4 @@
/* { dg-options "-O2 -w" } */
int a;
long b;
void c() { b = -9223372036854775807L - 1 - a; }