flang vs gfortran compiling same code with -flto flag flang runs into /usr/bin/ld: /usr/bin/../lib/LLVMgold.so: error loading plugin: /usr/bin/../lib/LLVMgold.so: cannot open shared object file: No such file or directory

[iajzenszmi]

flang vs gfortran compiling same code with -flto flag flang runs into /usr/bin/ld: /usr/bin/../lib/LLVMgold.so: error loading plugin: /usr/bin/../lib/LLVMgold.so: cannot open shared object file: No such file or directory

(base) ian@ian-Aspire-One-753:/CodeCode/CodeCode$ flang xspline.f -flto -o xspline
/usr/bin/ld: /usr/bin/../lib/LLVMgold.so: error loading plugin: /usr/bin/../lib/LLVMgold.so: cannot open shared object file: No such file or directory
flang-7: error: linker command failed with exit code 1 (use -v to see invocation)
(base) ian@ian-Aspire-One-753:/CodeCode/CodeCode$ gfortran xspline.f -flto -o xspline
(base) ian@ian-Aspire-One-753:/CodeCode/CodeCode$ ./xspline
SECOND - DERIVATIVES FOR SIN(X) FROM 0 TO PI
SPLINE ACTUAL
ANGLE 2ND DERIV 2ND DERIV
0.16 -0.156832 -0.156434
0.31 -0.309631 -0.309017
0.47 -0.454933 -0.453991
0.63 -0.588991 -0.587785
0.79 -0.708561 -0.707107
0.94 -0.810683 -0.809017
1.10 -0.892844 -0.891007
1.26 -0.953009 -0.951057
1.41 -0.989721 -0.987688
1.57 -1.002061 -1.000000
1.73 -0.989715 -0.987688
1.88 -0.953020 -0.951056
2.04 -0.892835 -0.891006
2.20 -0.810685 -0.809017
2.36 -0.708558 -0.707107
2.51 -0.588999 -0.587785
2.67 -0.454920 -0.453990
2.83 -0.309660 -0.309017
2.98 -0.156736 -0.156434
3.14 -0.000075 0.000000
(base) ian@ian-Aspire-One-753:/CodeCode/CodeCode$
(base) ian@ian-Aspire-One-753:/CodeCode/CodeCode$ cat xspline.f
PROGRAM XSPLINE
C PAGE 33 NUMERICAL RECIPIES EXAMPLE BOOK SECOND EDITION.
C DRIVER FOR ROUTINE SPLINE
INTEGER N
REAL PI
PARAMETER(N=20,PI=3.141593)
INTEGER I
REAL YPI, YPN, X(N),Y(N),Y2(N)
WRITE(,) 'SECOND - DERIVATIVES FOR SIN(X) FROM 0 TO PI'
C GENERATE ARRAY FOR INTERPOLATION
C
DO 11 I=1,20
X(I)=IPI/N
Y(I)=SIN(X(I))
11 CONTINUE
C
C CALCULATE 2ND DERIVATIVE WITH SPLINE
C
YP1=COS(X(1))
YPN=COS(X(N))
CALL SPLINE(X,Y,N,YP1,YPN,Y2)
C TEST RESULT
WRITE(,'(T19,A,T35,A)') 'SPLINE','ACTUAL'
WRITE(,'(T6,A,T17,A,T33,A)') 'ANGLE','2ND DERIV','2ND DERIV'
DO 12 I = 1, N
WRITE(,'(1X,F8.2,2F16.6)') X(I),Y2(I),-SIN(X(I))
12 CONTINUE
END PROGRAM
SUBROUTINE SPLINE(X,Y,N,YP1,YPN,Y2)
PARAMETER (NMAX=100)
DIMENSION X(N),Y(N),Y2(N),U(NMAX)
IF (YP1.GT..99E30) THEN
Y2(1)=0.0
U(1)=0.0
ELSE
Y2(1)=-0.5
U(1)=(3./(X(2)-X(1)))((Y(2)-Y(1))/(X(2)-X(1))-YP1)
ENDIF
DO 11 I=2,N-1
SIG=(X(I)-X(I-1))/(X(I+1)-X(I-1))
P=SIGY2(I-1)+2.
Y2(I)=(SIG-1.)/P
U(I) = (6.((Y(I+1)-Y(I))/(X(I+1)-X(I))-(Y(I)-Y(I-1))
* /(X(I)-X(I-1)))/(X(I+1)-X(I-1))-SIGU(I-1))/P
11 CONTINUE
IF (YPN.GT..99E30) THEN
QN=0.
UN=0.
ELSE
QN=0.5
UN=(3./(X(N)-X(N-1)))(YPN-(Y(n)-Y(N-1))/(X(N)-X(N-1)))
ENDIF
Y2(N)=(UN-QNU(N-1))/(QN*Y2(N-1)+1.)
DO 12 K=N-1,1,-1
Y2(K)=Y2(K)*Y2(K+1)+U(K)
12 CONTINUE
RETURN
END SUBROUTINE
(base) ian@ian-Aspire-One-753:/CodeCode/CodeCode$

[bryanpkc]

You need to make sure that the LLVM build can generate LLVMgold.so. If I remember correctly, you need to make sure that binutils headers (specifically plugin-api.h) can be found on the system; on Ubuntu that would require running apt install binutils-dev. You might need to point LLVM's CMake files at the location of the header with the variable LLVM_BINUTILS_INCDIR. Finally, you should probably also enable building lld when configuring LLVM, by adding lld to LLVM_ENABLE_PROJECTS when running CMake.

[pawosm-arm]

This isn't actual issue. LTO works fine with classic flang, we're using it a lot with no trouble, so I'm closing this one.