[PATCH] aarch64: increase alias candidate limit in aarch64-gen

[Muhammad Kamran]

On 21/08/2026 11:36, Richard Earnshaw (foss) wrote:
> On 19/08/2026 09:23, Muhammad Kamran wrote:
>> Increase max_num_aliases from 32 to 64 so that aarch64-gen can
>> accommodate the additional HINT-space alias added for FEAT_PAuth_LR.
>>
> 
> What were the symptoms of the overflow? A build time failure, a run-time assert, or crash, or just garbled output?
> 

The overflow shows up as a build-time failure while regenerating the
generated AArch64 opcode files.  The FEAT_PAuth_LR HINT-space alias
(yet to be posted) increases the number of aliases matching the same
encoding group, and find_alias_opcode trips:

   assert (i < max_num_aliases)

For instance,
$ aarch64-gen --gen-dis > $(binutils)/opcodes/aarch64-dis-2.c
aarch64-gen: /work/src/binutils/opcodes/aarch64-gen.c:813: 
find_alias_opcode: Assertion `i < max_num_aliases' failed.
Aborted

> 
>> The generated disassembler alias preference list can otherwise exceed
>> the old fixed limit.
>> ---
>>   opcodes/aarch64-gen.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/opcodes/aarch64-gen.c b/opcodes/aarch64-gen.c
>> index a387cd4a1e0..abe4147f2c4 100644
>> --- a/opcodes/aarch64-gen.c
>> +++ b/opcodes/aarch64-gen.c
>> @@ -789,8 +789,8 @@ opcode_node *
>>   find_alias_opcode (const aarch64_opcode *opcode)
>>   {
>>     int i;
>> -  /* Assume maximum of 32 disassemble preference candidates.  */
>> -  const int max_num_aliases = 32;
>> +  /* Assume maximum of 64 disassemble preference candidates.  */
>> +  const int max_num_aliases = 64;
>>     const aarch64_opcode *ent;
>>     const aarch64_opcode *preferred[max_num_aliases + 1];
>>     opcode_node head, **next;
>