On Thu, 2023-08-17 at 15:20 +0800, Chenghui Pan wrote: > Seems ARMv8-A only guarantees to preserve low 64-bit value of > NEON/floating-point register value. I'm not sure that I modify the > testcase in the right way and maybe we need more investigations. Any > ideas or suggestion?
Sorry, the following sentence in GCC manual section 6.47.5.2 suggests my test case is not valid: "As with global register variables, it is recommended that you choose a register that is normally saved and restored by function calls on your machine, so that calls to library routines will not clobber it." So when I use asm(name), the compiler has no obligation to guarantee that it will ever work like a normal variable after a function call. But I still need to verify that the compiler correctly understands only the low 64 bits of the vector register is saved. I'll try to make another test case... -- Xi Ruoyao <xry...@xry111.site> School of Aerospace Science and Technology, Xidian University
