RE: [r16-5628 Regression] FAIL: g++.target/i386/vect-pragma-target-2.C -std=gnu++20 (test for excess errors) on Linux/x86_64

> From: Jiang, Haochen <[email protected]>
> Sent: Thursday, November 27, 2025 4:47 AM
> 
> On Linux/x86_64,
> 
> 004438857554f47eb5491d59b067e56fdacf0e74 is the first bad commit
> commit 004438857554f47eb5491d59b067e56fdacf0e74
> Author: Jakub Jelinek <[email protected]>
> Date:   Wed Nov 26 15:01:11 2025 +0100
> 
>     Change the default C++ dialect to gnu++20
> 
> caused
> 
> FAIL: g++.target/i386/mv28.C  -std=c++20  (test for errors, line 10)
> FAIL: g++.target/i386/mv28.C  -std=c++20  (test for errors, line 11)
> FAIL: g++.target/i386/mv28.C  -std=c++20  (test for errors, line 12)
> FAIL: g++.target/i386/mv28.C  -std=c++20  (test for errors, line 13)
> FAIL: g++.target/i386/mv28.C  -std=c++20  (test for errors, line 14)
> FAIL: g++.target/i386/mv28.C  -std=c++20  (test for errors, line 15)
> FAIL: g++.target/i386/mv28.C  -std=c++20  (test for errors, line 4)
> FAIL: g++.target/i386/mv28.C  -std=c++20  (test for errors, line 5)
> FAIL: g++.target/i386/mv28.C  -std=c++20  (test for errors, line 6)
> FAIL: g++.target/i386/mv28.C  -std=c++20  (test for errors, line 7)
> FAIL: g++.target/i386/mv28.C  -std=c++20  (test for errors, line 8)
> FAIL: g++.target/i386/mv28.C  -std=c++20  (test for errors, line 9)
> FAIL: g++.target/i386/mv28.C  -std=c++26  (test for errors, line 10)
> FAIL: g++.target/i386/mv28.C  -std=c++26  (test for errors, line 11)
> FAIL: g++.target/i386/mv28.C  -std=c++26  (test for errors, line 12)
> FAIL: g++.target/i386/mv28.C  -std=c++26  (test for errors, line 13)
> FAIL: g++.target/i386/mv28.C  -std=c++26  (test for errors, line 14)
> FAIL: g++.target/i386/mv28.C  -std=c++26  (test for errors, line 15)
> FAIL: g++.target/i386/mv28.C  -std=c++26  (test for errors, line 4)
> FAIL: g++.target/i386/mv28.C  -std=c++26  (test for errors, line 5)
> FAIL: g++.target/i386/mv28.C  -std=c++26  (test for errors, line 6)
> FAIL: g++.target/i386/mv28.C  -std=c++26  (test for errors, line 7)
> FAIL: g++.target/i386/mv28.C  -std=c++26  (test for errors, line 8)
> FAIL: g++.target/i386/mv28.C  -std=c++26  (test for errors, line 9)
> FAIL: g++.target/i386/mv28.C  -std=c++98  (test for errors, line 10)
> FAIL: g++.target/i386/mv28.C  -std=c++98  (test for errors, line 11)
> FAIL: g++.target/i386/mv28.C  -std=c++98  (test for errors, line 12)
> FAIL: g++.target/i386/mv28.C  -std=c++98  (test for errors, line 13)
> FAIL: g++.target/i386/mv28.C  -std=c++98  (test for errors, line 14)
> FAIL: g++.target/i386/mv28.C  -std=c++98  (test for errors, line 15)
> FAIL: g++.target/i386/mv28.C  -std=c++98  (test for errors, line 4)
> FAIL: g++.target/i386/mv28.C  -std=c++98  (test for errors, line 5)
> FAIL: g++.target/i386/mv28.C  -std=c++98  (test for errors, line 6)
> FAIL: g++.target/i386/mv28.C  -std=c++98  (test for errors, line 7)
> FAIL: g++.target/i386/mv28.C  -std=c++98  (test for errors, line 8)
> FAIL: g++.target/i386/mv28.C  -std=c++98  (test for errors, line 9)
> FAIL: g++.target/i386/pr82625.C  -std=gnu++20  scan-tree-dump-times
> optimized "return 4096;" 1
> FAIL: g++.target/i386/pr82625.C  -std=gnu++20  scan-tree-dump-times
> optimized "return 8192;" 1
> FAIL: g++.target/i386/pr82625.C  -std=gnu++26  scan-tree-dump-times
> optimized "return 4096;" 1
> FAIL: g++.target/i386/pr82625.C  -std=gnu++26  scan-tree-dump-times
> optimized "return 8192;" 1
> FAIL: g++.target/i386/pr82625.C  -std=gnu++98  scan-tree-dump-times
> optimized "return 4096;" 1
> FAIL: g++.target/i386/pr82625.C  -std=gnu++98  scan-tree-dump-times
> optimized "return 8192;" 1
> FAIL: g++.target/i386/vect-pragma-target-1.C  -std=gnu++20  scan-assembler-
> times vpaddw.+zmm[0-9]+ 1
> FAIL: g++.target/i386/vect-pragma-target-1.C  -std=gnu++26  scan-assembler-
> times vpaddw.+zmm[0-9]+ 1
> FAIL: g++.target/i386/vect-pragma-target-1.C  -std=gnu++98  scan-assembler-
> times vpaddw.+zmm[0-9]+ 1
> 

I guess those are quite fragile but we need to fix them with some solution.

I will help have a look into that.

Thx,
Haochen

> with GCC configured with
> 
> ../../gcc/configure --prefix=/export/users3/haochenj/src/gcc-
> bisect/master/master/r16-5628/usr --enable-clocale=gnu --with-system-zlib -
> -with-demangler-in-ld --with-fpmath=sse --enable-languages=c,c++,fortran --
> enable-cet --without-isl --enable-libmpx x86_64-linux --disable-bootstrap
> 
> To reproduce:
> 
> $ cd {build_dir}/gcc && make check
> RUNTESTFLAGS="i386.exp=g++.target/i386/mv28.C --target_board='unix{-
> m32\ -march=cascadelake}'"
> $ cd {build_dir}/gcc && make check
> RUNTESTFLAGS="i386.exp=g++.target/i386/mv28.C --target_board='unix{-
> m64\ -march=cascadelake}'"
> $ cd {build_dir}/gcc && make check
> RUNTESTFLAGS="i386.exp=g++.target/i386/pr82625.C --target_board='unix{-
> m32\ -march=cascadelake}'"
> $ cd {build_dir}/gcc && make check
> RUNTESTFLAGS="i386.exp=g++.target/i386/pr82625.C --target_board='unix{-
> m64\ -march=cascadelake}'"
> $ cd {build_dir}/gcc && make check
> RUNTESTFLAGS="i386.exp=g++.target/i386/vect-pragma-target-1.C --
> target_board='unix{-m32\ -march=cascadelake}'"
> $ cd {build_dir}/gcc && make check
> RUNTESTFLAGS="i386.exp=g++.target/i386/vect-pragma-target-1.C --
> target_board='unix{-m64\ -march=cascadelake}'"
> 
> (Please directly reply to this email for question about this report.)
> (If you met problems with cascadelake related, disabling AVX512F in
> command line might save that.)
> (However, please make sure that there is no potential problems with AVX512.)