[TSan] Improve handling of stack pointer mangling in {set,long}jmp, pt.6

[yln]

Summary

Since we don't clobber x1/w1 (2nd argument) anymore, we don't have to
save/restore it.

[dvyukov]

Rubber stamp LGTM, if you want a real review please ask somebody else. But if you are sure it's good and covered by tests, submit.

[yln]

In D64023#1566002, @dvyukov wrote:

Rubber stamp LGTM, if you want a real review please ask somebody else. But if you are sure it's good and covered by tests, submit.

I have learnt that one can never be 100% sure ;)

We have the following tests that cover this (--filter jmp):

PASS: ThreadSanitizer-arm64e-ios :: fiber_longjmp.cc (1 of 6)
PASS: ThreadSanitizer-arm64e-ios :: longjmp.cc (2 of 6)
PASS: ThreadSanitizer-arm64e-ios :: longjmp2.cc (3 of 6)
PASS: ThreadSanitizer-arm64e-ios :: longjmp3.cc (4 of 6)
PASS: ThreadSanitizer-arm64e-ios :: longjmp4.cc (5 of 6)
PASS: ThreadSanitizer-arm64e-ios :: signal_longjmp.cc (6 of 6)

[yln]

Still need to save/restore x1 (even if we don't clobber it ourselves).
Same as: https://reviews.llvm.org/D63946

compiler-rt/lib/tsan/rtl/tsan_rtl_aarch64.S

ASM_SYMBOL_INTERCEPTOR(setjmp):
 
   // call tsan interceptor
   bl      ASM_SYMBOL(__tsan_setjmp)
 
   // restore env parameter
   mov     x0, x19
   ldr     x19, [sp, 16]
   ldp     x29, x30, [sp], 32
-  CFI_RESTORE (30)
   CFI_RESTORE (19)
+  CFI_RESTORE (29)
+  CFI_RESTORE (30)
   CFI_DEF_CFA (31, 0)
 
   // tail jump to libc setjmp
 #if !defined(__APPLE__)
   adrp    x1, :got:_ZN14__interception11real_setjmpE
   ldr     x1, [x1, #:got_lo12:_ZN14__interception11real_setjmpE]
   ldr     x1, [x1]
 #else
ASM_SYMBOL_INTERCEPTOR(_setjmp):
 
   // call tsan interceptor
   bl      ASM_SYMBOL(__tsan_setjmp)
 
   // Restore jmp_buf parameter
   mov     x0, x19
   ldr     x19, [sp, 16]
   ldp     x29, x30, [sp], 32
-  CFI_RESTORE (30)
   CFI_RESTORE (19)
+  CFI_RESTORE (29)
+  CFI_RESTORE (30)
   CFI_DEF_CFA (31, 0)
 
   // tail jump to libc setjmp
 #if !defined(__APPLE__)
   adrp    x1, :got:_ZN14__interception12real__setjmpE
   ldr     x1, [x1, #:got_lo12:_ZN14__interception12real__setjmpE]
   ldr     x1, [x1]
 #else
ASM_SYMBOL_INTERCEPTOR(sigsetjmp):
   CFI_DEF_CFA_OFFSET (32)
   CFI_OFFSET (29, -32)
   CFI_OFFSET (30, -24)
 
   // Adjust the SP for previous frame
   add     x29, sp, 0
   CFI_DEF_CFA_REGISTER (29)
 
-  // Save jmp_buf and savesigs
-  stp     x19, x20, [sp, 16]
+  // Save jmp_buf
+  str     x19, [sp, 16]
   CFI_OFFSET (19, -16)
-  CFI_OFFSET (20, -8)
-  mov     w20, w1
   mov     x19, x0
 
   // Obtain SP, first argument to `void __tsan_setjmp(uptr sp)`
   add     x0, x29, 32
 
   // call tsan interceptor
   bl      ASM_SYMBOL(__tsan_setjmp)
 
   // restore env parameter
-  mov     w1, w20
   mov     x0, x19
-  ldp     x19, x20, [sp, 16]
+  ldr     x19, [sp, 16]
   ldp     x29, x30, [sp], 32
-  CFI_RESTORE (30)
-  CFI_RESTORE (29)
   CFI_RESTORE (19)
-  CFI_RESTORE (20)
+  CFI_RESTORE (29)
+  CFI_RESTORE (30)
   CFI_DEF_CFA (31, 0)
 
   // tail jump to libc sigsetjmp
 #if !defined(__APPLE__)
   adrp    x2, :got:_ZN14__interception14real_sigsetjmpE
   ldr     x2, [x2, #:got_lo12:_ZN14__interception14real_sigsetjmpE]
   ldr     x2, [x2]
 #else
ASM_SYMBOL_INTERCEPTOR(__sigsetjmp):
   CFI_DEF_CFA_OFFSET (32)
   CFI_OFFSET (29, -32)
   CFI_OFFSET (30, -24)
 
   // Adjust the SP for previous frame
   add     x29, sp, 0
   CFI_DEF_CFA_REGISTER (29)
 
-  // Save jmp_buf and savesigs
-  stp     x19, x20, [sp, 16]
+  // Save jmp_buf
+  str     x19, [sp, 16]
   CFI_OFFSET (19, -16)
-  CFI_OFFSET (20, -8)
-  mov     w20, w1
   mov     x19, x0
 
   // Obtain SP, first argument to `void __tsan_setjmp(uptr sp)`
   add     x0, x29, 32
 
   // call tsan interceptor
   bl      ASM_SYMBOL(__tsan_setjmp)
 
-  mov     w1, w20
+  // restore env parameter
   mov     x0, x19
-  ldp     x19, x20, [sp, 16]
+  ldr     x19, [sp, 16]
   ldp     x29, x30, [sp], 32
-  CFI_RESTORE (30)
-  CFI_RESTORE (29)
   CFI_RESTORE (19)
-  CFI_RESTORE (20)
+  CFI_RESTORE (29)
+  CFI_RESTORE (30)
   CFI_DEF_CFA (31, 0)
 
   // tail jump to libc __sigsetjmp
 #if !defined(__APPLE__)
   adrp    x2, :got:_ZN14__interception16real___sigsetjmpE
   ldr     x2, [x2, #:got_lo12:_ZN14__interception16real___sigsetjmpE]
   ldr     x2, [x2]
 #else