[Bug target/126382] [16/17 regression] Incorrect compiler generated code resulting in seg fault - hoisted tls() in x86_cse caused register clobbering

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126382

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2026-07-24

--- Comment #1 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Reshma Roy from comment #0)
> Created attachment 65120 [details]
> The preprocessed input file to be used for the command mentioned in the
> description
> 
> GCC version: gcc (GCC) 17.0.0 20260722 (experimental)
> 
> GCC trunk generates incorrect code for AVX stack-realigned functions. This
> causes a null pointer to dereference in libFLAME's legacy test suite
> during Hessenberg reduction (FLA_Obj_datatype_check.c:18).
> 
> Bisection points to 5cf1b9a03ec5b617af8c50c1e9c0d223083fd7f2 ("x86-64:
> Remove redundant TLS calls").
> 
> -----------------------------------------------------------------------------
> --
> Reduced test case:
> 
> typedef struct { long n; long m_inner; long n_inner; int base; } FLA_Obj;
> __thread FLA_Obj FLA_ONE, W12;
> long FLA_Obj_length ();
> void FLA_Obj_width ();
> void f (FLA_Obj A)
> {
>   while (FLA_Obj_length (A))
>     FLA_Obj_width (FLA_ONE);
>   FLA_Obj_width (FLA_ONE, W12);
> }
> 
> Reproducer: gcc -mtune=native -O3 -mavx512f -mavx512dq -mfma
> -fstack-protector-strong -fpie -std=c11 -fPIC -S -o testcase.s testcase.i
> 

Please show the output of

$ gcc -v -mtune=native -O3 -mavx512f -mavx512dq -mfma -fstack-protector-strong
-fpie -std=c11 -fPIC -S -o testcase.s testcase.i