Here is a simplified reproducer for an optimizer bug of IFort 17.0 that was to blame for the bugs shown in a contemporary post (https://software.intel.com/en-us/forums/intel-visual-fortran-compiler-for-windows/topic/685333). The bug is rather fragile, and small changes to the code can make it go away. To reproduce the bug, put the sources into separate files, and compile the two files with the option /Ot or /O2. The bug is not seen if /Od is used, or with previous versions of the compiler.
Program TST IMPLICIT NONE INTEGER I REAL Array(8) DO I=1,8 Array(I)=I ENDDO call ArrayTest(array,8,1) END PROGRAM
SUBROUTINE ArrayTest(Array2D,Rows,Cols) IMPLICIT NONE INTEGER Rows,Cols INTEGER*2 J REAL Array2D(rows,cols),Array1D(rows) DO J=1,rows Array1D(J)=Array2D(J,1) ENDDO WRITE(*,'(A,12(1X,F8.4))') 'Array1D = ' + ,(Array1D(J),J=1,rows) RETURN END
The correct output is
Array1D = 1.0000 2.0000 3.0000 4.0000 5.0000 6.0000 7.0000 8.0000
but, because of the optimizer bug, the actual output is
Array1D = 1.0000 2.0000 3.0000 4.0000 1.0000 2.0000 3.0000 4.0000
Comparing the assembly listings obtained with /Ot with IFort 16and IFort 17 (both 32-bit) displays the code generation problem:
.B1.4: ; Preds .B1.4 .B1.3 movups xmm0, XMMWORD PTR [-4+edi+edx*4] ;9.10 movups xmm1, XMMWORD PTR [12+edi+edx*4] ;9.10 add eax, 8 ;8.7 movaps XMMWORD PTR [-4+esi+edx*4], xmm0 ;9.10 movaps XMMWORD PTR [12+esi+edx*4], xmm1 ;9.10 add edx, 8 ;10.7
.B1.4: ; Preds .B1.4 .B1.3 movups xmm0, XMMWORD PTR [-4+edi+edx*4] ;9.10 add eax, 8 ;8.7 movups XMMWORD PTR [-4+esi+edx*4], xmm0 ;9.10 movups XMMWORD PTR [12+esi+edx*4], xmm0 ;9.10 add edx, 8 ;10.7
Thanks - I can reproduce this. Making the array index J default integer (INTEGER(4)) avoids the problem. I will send this on to the developers. Issue ID is DPD200414427.
No, it has not yet been fixed. I have pinged the developers to see where they are on it. There has been initial triage on it - the vectorizer is not handling the INTEGER(2) case here correctly.
I concur with mecej4. The issue is fixed in PSXE 2017 Update 2. I went back and re-tested his test case in reply #1 and the original test case from the forum post cited in post #1 and can show both now produce expected results with update 2.
If you are experiencing failures with update 2 then perhaps you have a variant on the original issue or a different issue in which case please provide the details requested and a complete reproducer that we can investigate further.