| Message ID | Za5SnK4O+RTJClzB@tucnak |
|---|---|
| State | New |
| Headers | show |
| Series | fold-const: Fold larger VIEW_CONVERT_EXPRs [PR113462] | expand |
On Mon, 22 Jan 2024, Jakub Jelinek wrote: > Hi! > > On Mon, Jan 22, 2024 at 11:56:11AM +0100, Richard Biener wrote: > > > 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. > > > Perhaps we could use XALLOCAVEC there instead (or use it only for the > > > larger sizes and keep the static buffer for the common case). > > > > Well, yes. V_C_E folding could do this but then the native_encode_expr > > API could also allow lazy allocation or so. > > native_encode_expr can't reallocate, it has to fill in whatever buffer it > has been called with, it can be in the middle of something else etc. > > The following patch is what I meant, I think having some upper bound is > desirable so that we don't spend too much time trying to VCE fold 2GB > structures (after all, the APIs also use int for lengths) and similar and passed > make check-gcc check-g++ -j32 -k GCC_TEST_RUN_EXPENSIVE=1 RUNTESTFLAGS="GCC_TEST_RUN_EXPENSIVE=1 dg.exp='*bitint* pr112673.c builtin-stdc-bit-*.c pr112566-2.c pr112511.c' dg-torture.exp=*bitint* dfp.exp=*bitint*" > (my usual quick test for bitint related changes). Ok for trunk if it passes > full bootstrap/regtest? OK. Thanks, Richard. > 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. > > --- gcc/fold-const.cc.jj 2024-01-12 10:07:58.202851544 +0100 > +++ gcc/fold-const.cc 2024-01-22 12:09:05.116253393 +0100 > @@ -8773,8 +8773,7 @@ native_interpret_int (tree type, const u > 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 > 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 > 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 > > > Jakub > >
--- gcc/fold-const.cc.jj 2024-01-12 10:07:58.202851544 +0100 +++ gcc/fold-const.cc 2024-01-22 12:09:05.116253393 +0100 @@ -8773,8 +8773,7 @@ native_interpret_int (tree type, const u 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 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 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