On 23/05/16 12:27, Richard Biener wrote:
On Mon, May 23, 2016 at 1:17 PM, Kyrill Tkachov
<kyrylo.tkac...@foss.arm.com> wrote:
Hi all,
In this PR we end up hitting a signed overflow in noce_get_alt_condition
when we try to
increment or decrement a HOST_WIDE_INT that might be HOST_WIDE_INT_MAX or
HOST_WIDE_INT_MIN.
I've confirmed the overflow by adding an assert before the operation:
gcc_assert (desired_val != HOST_WIDE_INT_MAX);
This patch fixes those cases by catching the cases when desired_val has the
extreme
value and avoids the transformation that function is trying to make.
Bootstrapped and tested on arm, aarch64, x86_64.
I've added the testcase that I used to trigger the assert mentioned above as
a compile test,
though I'm not sure how much value it has...
Ok for trunk?
If this isn't also a wrong-code issue (runtime testcase?) then why not perform
the operation in unsigned HOST_WIDE_INT instead?
This part of the code transforms a comparison "x < CST" to "x <= CST - 1"
and similar transformations. Fro what I understand the LT,LE,GT,GE RTL
comparison
operators operate on signed integers, so I'm not sure how valid it would be
to do all this on unsigned HOST_WIDE_INT.
Thanks,
Kyrill
Richard.
Thanks,
Kyrill
2016-05-23 Kyrylo Tkachov <kyrylo.tkac...@arm.com>
PR rtl-optimization/66940
* ifcvt.c (noce_get_alt_condition): Check that incrementing or
decrementing desired_val will not overflow before performing these
operations.
2016-05-23 Kyrylo Tkachov <kyrylo.tkac...@arm.com>
PR rtl-optimization/66940
* gcc.c-torture/compile/pr66940.c: New test.