Hi, ALL
We have a question for your help:
1. We have two platforms, both of which are ARM64, one of which supports
both NEON and SVE, the other only support NEON.
2. We want to run on both platforms with a single binary file, and use the
highest vector capability of the corresponding platform whenever possible.
3. So we build the DPDK program with -march=armv8-a+sve+crc (GCC 10.2).
However, it is found that invalid instructions occur when the program
runs on a machine that does not support SVE (pls see below).
4. The problem is caused by the introduction of SVE in GCC automatic vector
optimization.
So Is there a way to disable GCC automatic vector optimization or use only
NEON to perform automatic vector optimization?
BTW: we already test -fno-tree-vectorize (as link below) but found no effect.
https://stackoverflow.com/questions/7778174/how-can-i-disable-vectorization-while-using-gcc
The GDB output:
EAL: Detected 128 lcore(s)
EAL: Detected 4 NUMA nodes
Option -w, --pci-whitelist is deprecated, use -a, --allow option instead
Program received signal SIGILL, Illegal instruction.
0x0000000000671b88 in eal_adjust_config ()
(gdb)
(gdb) where
#0 0x0000000000671b88 in eal_adjust_config ()
#1 0x0000000000682840 in rte_eal_init ()
#2 0x000000000051c870 in main ()
(gdb)
The disassembly output of eal_adjust_config:
671b7c: f8237a81 str x1, [x20, x3, lsl #3]
671b80: f110001f cmp x0, #0x400
671b84: 54ffff21 b.ne 671b68 <eal_adjust_config+0x1f4> //
b.any
671b88: 043357f5 addvl x21, x19, #-1
671b8c: 043457e1 addvl x1, x20, #-1
671b90: 910562b5 add x21, x21, #0x158
671b94: 04e0e3e0 cntd x0
671b98: 914012b5 add x21, x21, #0x4, lsl #12
671b9c: 52800218 mov w24, #0x10 //
#16
671ba0: 25d8e3e1 ptrue p1.d
671ba4: 25f80fe0 whilelo p0.d, wzr, w24
671ba8: a5e04020 ld1d {z0.d}, p0/z, [x1, x0, lsl #3]
Best regards.
