diff mbox series

lower-bitint: Fix up .{ADD,SUB}_OVERFLOW lowering

Message ID ZcdJ1WGHQm73I8eU@tucnak
State New
Headers show
Series lower-bitint: Fix up .{ADD,SUB}_OVERFLOW lowering | expand

Commit Message

Jakub Jelinek Feb. 10, 2024, 10:03 a.m. UTC 
Hi!

torture/bitint-37.c test FAILed on i686-linux e.g. on
signed _BitInt(575) + unsigned _BitInt(575) -> signed _BitInt(575)
__builtin_add_overflow.  With 64-bit limbs, we use 4 .UADDC calls in
the IL, 2 in a loop (which handles the first 8 limbs), then one partial
limb (we use 63 bits from that) and finally last_ovf case due to the
mixing of signed vs. unsigned.
But with 32-bit limbs, we use 5 .UADDC calls in the IL, 2 in a loop (which
handles the first 16 limbs), then one full limb above that, one partial
(31 bits) and finally last_ovf case, and for the last_ovf case the code
computed incorrect idx and so partly did the wrong thing, e.g. overwrote
the result from the previous .UADDC.

Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk?

2024-02-10  Jakub Jelinek  <jakub@redhat.com>

	* gimple-lower-bitint.cc (itint_large_huge::lower_addsub_overflow): Fix
	computation of idx for i == 4 of bitint_prec_huge.


	Jakub

Comments

Richard Biener Feb. 10, 2024, 11:43 a.m. UTC | #1 
> Am 10.02.2024 um 11:03 schrieb Jakub Jelinek <jakub@redhat.com>:
> 
> Hi!
> 
> torture/bitint-37.c test FAILed on i686-linux e.g. on
> signed _BitInt(575) + unsigned _BitInt(575) -> signed _BitInt(575)
> __builtin_add_overflow.  With 64-bit limbs, we use 4 .UADDC calls in
> the IL, 2 in a loop (which handles the first 8 limbs), then one partial
> limb (we use 63 bits from that) and finally last_ovf case due to the
> mixing of signed vs. unsigned.
> But with 32-bit limbs, we use 5 .UADDC calls in the IL, 2 in a loop (which
> handles the first 16 limbs), then one full limb above that, one partial
> (31 bits) and finally last_ovf case, and for the last_ovf case the code
> computed incorrect idx and so partly did the wrong thing, e.g. overwrote
> the result from the previous .UADDC.
> 
> Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
> trunk?

Ok

Richard 

> 2024-02-10  Jakub Jelinek  <jakub@redhat.com>
> 
>    * gimple-lower-bitint.cc (itint_large_huge::lower_addsub_overflow): Fix
>    computation of idx for i == 4 of bitint_prec_huge.
> 
> --- gcc/gimple-lower-bitint.cc.jj    2024-02-09 16:16:55.335552760 +0100
> +++ gcc/gimple-lower-bitint.cc    2024-02-09 20:41:50.397455671 +0100
> @@ -4031,7 +4031,7 @@ bitint_large_huge::lower_addsub_overflow
>       if (kind != bitint_prec_huge)
>    idx = size_int (i);
>       else if (i >= 2)
> -    idx = size_int (fin + (i > 2));
> +    idx = size_int (fin + i - 2);
>       if (!last_ovf || i < cnt - 1)
>    {
>      if (type0 != TREE_TYPE (arg0))
> 
>    Jakub
>
diff mbox series

Patch

--- gcc/gimple-lower-bitint.cc.jj	2024-02-09 16:16:55.335552760 +0100
+++ gcc/gimple-lower-bitint.cc	2024-02-09 20:41:50.397455671 +0100
@@ -4031,7 +4031,7 @@  bitint_large_huge::lower_addsub_overflow
       if (kind != bitint_prec_huge)
 	idx = size_int (i);
       else if (i >= 2)
-	idx = size_int (fin + (i > 2));
+	idx = size_int (fin + i - 2);
       if (!last_ovf || i < cnt - 1)
 	{
 	  if (type0 != TREE_TYPE (arg0))