Arm64/Sve: Sve_Multiply tests failing

[a74nh]

When I run all the SVE tests, the Sve_Multiply cause a segfault.

This is on Ubuntu Linux.

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[SwapnilGaikwad]

Adding a failure log for reference

Beginning scenario: RunBasicScenario_UnsafeRead
Process terminated. InternalError
   at System.Environment.FailFast(System.Runtime.CompilerServices.StackCrawlMarkHandle, System.String, System.Runtime.CompilerServices.ObjectHandleOnStack, System.String)
   at System.Environment.FailFast(System.Threading.StackCrawlMark ByRef, System.String, System.Exception, System.String)
   at System.Environment.FailFast(System.String)
   at System.Runtime.EH.FallbackFailFast(System.Runtime.RhFailFastReason, System.Object)
   at System.Runtime.EH.RhThrowHwEx(UInt32, ExInfo ByRef)
   at JIT.HardwareIntrinsics.Arm._Sve.SimpleBinaryOpTest__Sve_Multiply_sbyte.RunBasicScenario_UnsafeRead()
   at JIT.HardwareIntrinsics.Arm._Sve.Program.Sve_Multiply_sbyte()
   at Program.<<Main>$>g__TestExecutor3399|0_3400(System.IO.StreamWriter, System.IO.StreamWriter, <>c__DisplayClass0_0 ByRef)
   at Program.<Main>$(System.String[])
Aborted (core dumped)

[a74nh]

❯ gdb --args $CORE_ROOT/corerun ./artifacts/tests/coreclr/linux.arm64.Checked/JIT/HardwareIntrinsics/HardwareIntrinsics_Arm_ro/HardwareIntrinsics_Arm_ro.dll Sve_Multiply_sbyte
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Reading symbols from /home/alahay01/dotnet/runtime_sve/artifacts/tests/coreclr/linux.arm64.Checked/Tests/Core_Root/corerun...
(gdb) r
Starting program: /home/alahay01/dotnet/runtime_sve/artifacts/tests/coreclr/linux.arm64.Checked/Tests/Core_Root/corerun ./artifacts/tests/coreclr/linux.arm64.Checked/JIT/HardwareIntrinsics/HardwareIntrinsics_Arm_ro/HardwareIntrinsics_Arm_ro.dll Sve_Multiply_sbyte
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/aarch64-linux-gnu/libthread_db.so.1".
[New Thread 0xfffff6f1f100 (LWP 3134350)]
[New Thread 0xfffff670f100 (LWP 3134351)]
[New Thread 0xfffff5eff100 (LWP 3134352)]
[New Thread 0xfffff56ef100 (LWP 3134353)]
[New Thread 0xfffff4ecf100 (LWP 3134354)]
[New Thread 0xffffa7fff100 (LWP 3134355)]
[New Thread 0xffffa77ef100 (LWP 3134357)]
[New Thread 0xffffa57ff100 (LWP 3134358)]
[New Thread 0xffbef73ff100 (LWP 3134375)]
16:09:25.711 Running test: _Sve_ro::JIT.HardwareIntrinsics.Arm._Sve.Program.Sve_Multiply_sbyte()
Supported ISAs:
  AdvSimd:   True
  Aes:       True
  ArmBase:   True
  Crc32:     True
  Dp:        True
  Rdm:       True
  Sha1:      True
  Sha256:    True
  Sve:       True

Beginning scenario: RunBasicScenario_UnsafeRead

Thread 1 "corerun" received signal SIGILL, Illegal instruction.
0x0000ffffaaf4998c in ?? ()
(gdb) bt
#0  0x0000ffffaaf4998c in ?? ()
#1  0x0000ffffaaf47988 in ?? ()
Backtrace stopped: previous frame inner to this frame (corrupt stack?)
(gdb) disassemble 0x0000ffffaaf4996c,0x0000ffffaaf4999c
Dump of assembler code from 0xffffaaf4996c to 0x0000ffffaaf4999c:
   0x0000ffffaaf4996c:	add	x0, x0, #0x50
   0x0000ffffaaf49970:	mov	x1, #0x4b58                	// #19288
   0x0000ffffaaf49974:	movk	x1, #0xab21, lsl #16
   0x0000ffffaaf49978:	movk	x1, #0xffff, lsl #32
   0x0000ffffaaf4997c:	ldr	x1, [x1]
   0x0000ffffaaf49980:	blr	x1
   0x0000ffffaaf49984:	ldr	q16, [x0]
   0x0000ffffaaf49988:	ldr	q17, [x29, #48]
=> 0x0000ffffaaf4998c:	mul	z17.b, z17.b, z16.b
   0x0000ffffaaf49990:	str	q17, [x29, #64]
   0x0000ffffaaf49994:	ldr	x0, [x29, #88]
   0x0000ffffaaf49998:	ldrsb	wzr, [x0]
   0x0000ffffaaf4999c:	ldr	x0, [x29, #88]

Strange - generates a SIGILL, but gdb still thinks it is a valid instruction.

[a74nh]

This is because the unpredicated version of multiply is SVE2:
https://docsmirror.github.io/A64/2023-09/mul_z_zz.html

Instead, we should use the predicated version:
https://docsmirror.github.io/A64/2023-09/mul_z_p_zz.html