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* [gcc r14-8349] fold-const: Fold larger VIEW_CONVERT_EXPRs [PR113462]
@ 2024-01-23 8:05 Jakub Jelinek
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From: Jakub Jelinek @ 2024-01-23 8:05 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:5015015ae6b29b3f1734c7693ba25b88cdd531a1
commit r14-8349-g5015015ae6b29b3f1734c7693ba25b88cdd531a1
Author: Jakub Jelinek <jakub@redhat.com>
Date: Tue Jan 23 09:02:48 2024 +0100
fold-const: Fold larger VIEW_CONVERT_EXPRs [PR113462]
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.
Diff:
---
gcc/fold-const.cc | 22 +++++++++++++++++-----
1 file changed, 17 insertions(+), 5 deletions(-)
diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
index 385e4a69ab3..1fd957288d4 100644
--- a/gcc/fold-const.cc
+++ b/gcc/fold-const.cc
@@ -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
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