Loop fusion

The loop fusion transformation moves the body of a do-loop statement in another do-loop statement.

$\vartriangleright$ Example 63: 

    DO I=1,N
      PRINT *,I
    ENDDO 
    DO I=1,N
      A[I] = F(I)+1 
    ENDDO

$\longrightarrow$

    DO I=1,N
      PRINT *,I
      A[I] = F(I)+1 
    ENDDO

  $\blacktriangleright$ Fits:LoopFusion:Check(LOOP DIAGMESG LOOP2)

 
This function check if the fusion of two do-loop statements is allowed.

• LOOP (input AST) must be the first do-loop statement.
• DIAGMESG (output STRING) is a diagnostic string for the user.
• LOOP2 (input AST) must be the second do-loop statement.
• The function returns an error code (return INT):
  • 1 if all is correct
  • 0 if LOOP is not a do-loop statement
  • -1 if LOOP contains statements not handled by the transformation.
  • -2 if LOOP2 is not a do-loop statement
  • -3 if LOOP2 contains statements not handled by the transformation.
  • -4 if the bounds or the steps of LOOP and LOOP2 are not compatibles.
  • -5 if LOOP and LOOP2 are not in the same sequence of statements

  $\blacktriangleright$ Fits:LoopFusion:Advice(LOOP DIAGMESG LOOP2)

 
This function emits a diagnostic about the interest of the fusion of LOOP2 into LOOP.

• LOOP (input AST) must be a do-loop statement.
• DIAGMESG (output STRING) is a diagnostic string for the user.
• LOOP2 (input AST) must be the second do-loop statement.
• The function returns a diagnostic code (return INT) :
  • 1 if the transformation is recommended.
  • 0 if the transformation may be interesting.
  • -1 if the transformation in not recommended.

  $\blacktriangleright$ Fits:LoopFusion:Safe(LOOP,DIAGMESG,LOOP2)

 
This functions check if the fusion of LOOP2 in LOOP is safe.

• LOOP (input AST) must be a do-loop statement.
• DIAGMESG (output STRING) is a diagnostic string for the user
• LOOP2 (input AST) must be the second do-loop statement.
• The function returns a diagnostic code (return INT) :
  • 1 if the transformation is safe
  • 0 if the transformation may be safe. More informations are given by the text in DIAGMESG.
  • -1 if the transformation is not safe

  $\blacktriangleright$ Fits:LoopFusion:Apply(LOOP,VERBOSE,LOOP2)

 
This function applies the loop fusion transformation.

• LOOP (input AST) must be a do-loop statement.
• VERBOSE (input INT) is the comment level
• LOOP2 (input AST) must be the second do-loop statement.
• The function returns the do-loop statement created by the fusion (return AST)