FreeChainXenon/gcc
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

fold-const: Fold larger VIEW_CONVERT_EXPRs [PR113462]

Browse source 
On Mon, Jan 22, 2024 at 11:27:52AM +0100, Richard Biener wrote:
> We run into
>
> static tree
> native_interpret_int (tree type, const unsigned char *ptr, int len)
> {
> ...
>   if (total_bytes > len
>       || total_bytes * BITS_PER_UNIT > HOST_BITS_PER_DOUBLE_INT)
>     return NULL_TREE;
>
> OTOH using a V_C_E to "truncate" a _BitInt looks wrong?  OTOH the
> check doesn't really handle native_encode_expr using the "proper"
> wide_int encoding however that's exactly handled.  So it might be
> a pre-existing issue that's only uncovered by large _BitInts
> (__int128 might show similar issues?)

I guess the || total_bytes * BITS_PER_UNIT > HOST_BITS_PER_DOUBLE_INT
conditions make no sense, all we care is whether it fits in the buffer
or not.
But then there is
fold_view_convert_expr
(and other spots) which use
  /* We support up to 1024-bit values (for GCN/RISC-V V128QImode).  */
  unsigned char buffer[128];
or something similar.
This patch fixes even that by using a XALLOCAVEC allocated buffer
if the type size is 129 .. 8192 bytes.

2024-01-22  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/113462
	* fold-const.cc (native_interpret_int): Don't punt if total_bytes
	is larger than HOST_BITS_PER_DOUBLE_INT / BITS_PER_UNIT.
	(fold_view_convert_expr): Use XALLOCAVEC buffers for types with
	sizes between 129 and 8192 bytes.
This commit is contained in:
Jakub Jelinek 2024-01-23 09:02:48 +01:00
parent f12317306e
commit 5015015ae6
1 changed files with 17 additions and 5 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

22
gcc/fold-const.cc
View file

@ -8773,8 +8773,7 @@ native_interpret_int (tree type, const unsigned char *ptr, int len)
else
total_bytes = GET_MODE_SIZE (SCALAR_INT_TYPE_MODE (type));
if (total_bytes > len
|| total_bytes * BITS_PER_UNIT > HOST_BITS_PER_DOUBLE_INT)
if (total_bytes > len)
return NULL_TREE;
wide_int result = wi::from_buffer (ptr, total_bytes);
@ -9329,9 +9328,10 @@ fold_view_convert_vector_encoding (tree type, tree expr)
static tree
fold_view_convert_expr (tree type, tree expr)
{
/* We support up to 1024-bit values (for GCN/RISC-V V128QImode). */
unsigned char buffer[128];
unsigned char *buf;
int len;
HOST_WIDE_INT l;
/* Check that the host and target are sane. */
if (CHAR_BIT != 8 || BITS_PER_UNIT != 8)
@ -9341,11 +9341,23 @@ fold_view_convert_expr (tree type, tree expr)
if (tree res = fold_view_convert_vector_encoding (type, expr))
return res;
len = native_encode_expr (expr, buffer, sizeof (buffer));
l = int_size_in_bytes (type);
if (l > (int) sizeof (buffer)
&& l <= WIDE_INT_MAX_PRECISION / BITS_PER_UNIT)
{
buf = XALLOCAVEC (unsigned char, l);
len = l;
}
else
{
buf = buffer;
len = sizeof (buffer);
}
len = native_encode_expr (expr, buf, len);
if (len == 0)
return NULL_TREE;
return native_interpret_expr (type, buffer, len);
return native_interpret_expr (type, buf, len);
}
/* Build an expression for the address of T. Folds away INDIRECT_REF