COMPILER TECHNIQUES FOR MATLAB PROGRAMS ... - CiteSeerX

eing performed (e.g., multiplication, left solve, right solve) and the shape of a and b. They
are then used to guide the allocation (or reallocation) of the array c, whenever necessary.
Notice that special consideration is taken with scalars when the variable is dynamically
allocated. The problem is that the Fortran 90 operation a b assumes the operands to be
conformable if they are dynamically allocated. Hence, if one of the operands is scalar and
if it is dynamically allocated as a 1 1 array, the operation as written above would result
in an error. Therefore, dynamic rank inference is necessary. As presented in Section 6.2.1,
this dynamic code can be optimized with the use of symbolic-propagation.
3.2.7 Code Generator
The nal phase of the MATLAB compiler generates Fortran 90. This pass is also divided
into two steps: the generation of declarations, and the generation of executable code.
The declarations are generated by traversing the symbol table.
Variables that have
unknown intrinsic type at the end of the static phase are declared twice: once for the real
instance of the variable, and once for the complex instance. Variables that have unknown
shape are declared as two-dimensional allocatable arrays. Shadow variables are generated
only for variables that have unknown shape or intrinsic type at the end of the static phase.
The generation of executable code is performed by traversing once more the AST in
lexicographic order. This pass is straightforward because our output language is a high-level
language and, therefore, we do not deal with most of the issues of code generation [ASU85].
Moreover, at this point, all necessary attributes for the code generation have been already
lled by the static and dynamic inference phases.
To maintain compatibility with the MATLAB interpreter, whenever possible 7 the compiler
generates function calls from the same libraries used by MATLAB (i.e., LINPACK
[DMBS79], LAPACK [ABB + 92], EISPACK [SBD + 76]).
7 The information on which library function is being used by theinterpreter is not always available. Also,
sometimes this information is provided with a note stating that the library function was modied.
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