xtb: ICE during compilation of constrain_pot.f90

[foxtran]

Hello!

I  have tried to compile xtb (https://github.com/grimme-lab/xtb). Unfortunately, with ifx 2024.1.0, I got ICE:

          #0 0x00000000023916e2
          #1 0x00000000023f5bc7
          #2 0x00000000023f5cf0
          #3 0x00007f232544fb50
          #4 0x0000000004394b15
          #5 0x0000000004395724
          #6 0x0000000004394bd1
          #7 0x0000000004391eec
          #8 0x000000000439099c
          #9 0x000000000438ffe2
         #10 0x000000000339c5af
         #11 0x000000000339c42d
         #12 0x000000000272fcd5
         #13 0x00000000023452ed
         #14 0x0000000002736dbd
         #15 0x000000000234505d
         #16 0x000000000272ea2a
         #17 0x000000000232eacf
         #18 0x000000000232cf52
         #19 0x00000000022d97eb
         #20 0x00000000024b171c
         #21 0x00007f232543bd85 __libc_start_main + 229
         #22 0x00000000021134e9

/home/c_lokgi/workdir/xtb/src/constrain_pot.f90: error #5633: **Internal compiler error: segmentation violation signal raised** Please report this error along with the circumstances in which it occurred in a Software Problem Report.  Note: File and line given may not be explicit cause of this error.
compilation aborted for /home/c_lokgi/workdir/xtb/src/constrain_pot.f90 (code 3)

Steps to reproduce:

git clone https://github.com/grimme-lab/xtb.git
cd xtb
cmake -Bbuild_ifx -DCMAKE_C_COMPILER=icx -DCMAKE_CXX_COMPILER=icpx -DCMAKE_Fortran_COMPILER=ifx -DCMAKE_BUILD_TYPE=Release -DCMAKE_C_FLAGS="-g" -DCMAKE_CXX_FLAGS="-g" -DCMAKE_Fortran_FLAGS="-g"
cd build_ifx
make -j$(nproc)

In this thread I will let you know what I will find

I have no idea was it fixed in later releases of ifx or not, so, everybody can try to reproduce

[foxtran]

Here is the diff, that resolves issue:

diff --git a/src/constrain_pot.f90 b/src/constrain_pot.f90
index 1ce0cdd..f45f7e3 100644
--- a/src/constrain_pot.f90
+++ b/src/constrain_pot.f90
@@ -173,7 +173,7 @@ subroutine constrain_dist(fix,n,at,xyz,g,e)
    real(wp),intent(inout) :: e
    real(wp),intent(inout) :: g(3,n)

-   integer i,j,k,l,m,mm
+   integer i,j,k,l,m,mm,idx
    real(wp)rij(3),dum,r0,r,vp(3),ra(3),rb(3)
    real(wp)va(3),vb(3),vc(3),vab(3),vcb(3),deda(3),dedc(3),dedb(3)
    real(wp)dda(3),ddb(3),ddc(3),ddd(3)
@@ -198,8 +198,10 @@ subroutine constrain_dist(fix,n,at,xyz,g,e)
       e=e+fix%fc*dum
       ff=fix%fc*fix%expo(m)*dum2
       dum=ff/r
-      g(:,j)=g(:,j)+dum*rij
-      g(:,i)=g(:,i)-dum*rij
+      do idx = 1, 3
+        g(idx,j)=g(idx,j)+dum*rij(idx)
+        g(idx,i)=g(idx,i)-dum*rij(idx)
+      end do

    enddo

@Igor_V_Intel, could you please have a look why ICE happens?

[foxtran]

The simpler patch is to check that `(i == j)` and skip those pairs. However, this check will never happen, but it helps compiler not to fail with something internal (most probably, vectorization).

See the patch here: https://github.com/grimme-lab/xtb/pull/1106/files

[Ron_Green]

Thanks for the git info.  I am able to see the ICE and am investigating.  

[Ron_Green]

This seems to be an issue we've been having with some codes and -g -traceback.  If you remove those it should build.  but of course I will isolate something to take to the developers. For me it is crashing on DO CONCURRENT, src/disp/ncoord.f90 line 437.  Again, it's the -g -traceback options triggering it. 

xtb/src/disp/ncoord.f90(437): error #5623: **Internal compiler error: internal abort** Please report this error along with the circumstances in which it occurred in a Software Problem Report.  Note: File and line given may not be explicit cause of this error.
      do concurrent(tx = -rep_cn(1):rep_cn(1), &
------^

s 

[Ron_Green]

The more recent compiler I'm using is having the issue with the mask-exp of the last index spec.  I can work around the issue with this change to src/disp/ncoord.f90

before

 437       do concurrent(tx = -rep_cn(1):rep_cn(1), &
 438             &       ty = -rep_cn(2):rep_cn(2), &
 439             &       tz = -rep_cn(3):rep_cn(3), &
 440             &       tx.ne.0 .or. ty.ne.0 .or. tz.ne.0)

after, this compiles w/o issue even with -g -traceback

 437       do concurrent(tx = -rep_cn(1):rep_cn(1), &
 438             &       ty = -rep_cn(2):rep_cn(2), &
 439             &       tz = -rep_cn(3):rep_cn(3), &
 440             &       (tx.ne.0 .or. ty.ne.0 .or. tz.ne.0))

The issue is that the parser is not recognizing your mask expression without the parenthesis, and it's only when -g -traceback is used.  This does cause a different code path in the parser and IR we generate because of that.  

I am doing some more tests with the public 2024.2.0 and upcoming 2025.0 early builds.

[Ron_Green]

Unfortunately, the only compiler that is able to compile ncoord.f90 is our main branch which is what we will use for 2025.1. But this compiler will not be public until later Q1 2025.  
I tested 2024.1.0, 2024.2.0, 2025.0.0 preview build (not public).  All 3 get the ICE.  the main branch nightly build needs the parens around the mask expression to work.

All of them will work if you can remove -g -traceback. 

I'd like to isolate this a bit further so that the mask expression does not require the parens, and there is something lurking with -g -traceback.  We've had other issues with traceback lately, as we have made some major changes to how we create IR for traceback. 

[foxtran]

@Ron_Green, do you see the issue with constrain_pot.f90 without my patch with your versions of ifx?