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nir: make static assert more flexible

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The static assert used in encode deref modes used the fact there was
less than 16 modes that we wanted to compress as an opportunity to reuse
MODE_ENC_GENERIC_BIT as it just happened to represent 16. However if we
add more than 16 modes i.e need to compress to 6 bits not 5 bits then
MODE_ENC_GENERIC_BIT becomes 32 and the logic in the assert breaks.

Instead we more precisely make sure MODE_ENC_GENERIC_BIT is large
enough to fit all but the last 4 generic modes and that the last 4 modes
defined in the enum are in fact the 4 generic modes.

Acked-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30654>
This commit is contained in:
Timothy Arceri 2024-08-14 15:18:53 +10:00 • committed by Marge Bot
parent 85a70bbc05
commit 08b93c841a
1 changed files with 10 additions and 1 deletions
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11
src/compiler/nir/nir_serialize.c
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@ -825,6 +825,7 @@ read_alu(read_ctx *ctx, union packed_instr header)
return alu;
}
#define NUM_GENERIC_MODES 4
#define MODE_ENC_GENERIC_BIT (1 << 4)
static nir_variable_mode
@ -848,8 +849,16 @@ encode_deref_modes(nir_variable_mode modes)
* can compress them by only storing the bit position. This, plus one bit
* to select encoding, lets us pack the entire bitfield in 5 bits.
*/
/* Assert that the modes we are compressing fit along with the generic bit
*/
STATIC_ASSERT((nir_num_variable_modes - NUM_GENERIC_MODES) <
MODE_ENC_GENERIC_BIT);
/* Assert that the generic modes are defined at the end of the modes enum
*/
STATIC_ASSERT((nir_var_all & ~nir_var_mem_generic) <
(1 << MODE_ENC_GENERIC_BIT));
(1 << (nir_num_variable_modes - NUM_GENERIC_MODES)));
unsigned enc;
if (modes == 0 || (modes & nir_var_mem_generic)) {