2004-11-02 Daniel Berlin <dberlin@dberlin.org>

	* lambda-code.c (lambda_compute_auxillary_space): Update comments.
	(lambda_compute_target_space). Ditto.
	* lambda.h (lambda_trans_matrix): Ditto.
	(lambda_linear_expression): Ditto.
	(lambda_body_vector): Ditto.
	(lambda_loopnest): Ditto.
	* tree-loop-linear.c (gather_interchange_stats): Combine tests,
	update comments, and remove pointless addition of 0.
	(linear_transform_loops): Update comments.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@90029 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 37 insertions, 5 deletions

diff --git a/gcc/lambda.h b/gcc/lambda.h
index b7360241acc..98fe6bd1ca6 100644
--- a/gcc/lambda.h
+++ b/gcc/lambda.h
@@ -29,11 +29,14 @@ Software Foundation, 59 Temple Place - Suite 330, Boston, MA
    and scalar multiplication.  In this vector space, an element is a list of
    integers.  */
 typedef int *lambda_vector;
+
 /* An integer matrix.  A matrix consists of m vectors of length n (IE
    all vectors are the same length).  */
 typedef lambda_vector *lambda_matrix;
 
-/* A transformation matrix.  */
+/* A transformation matrix, which is a self-contained ROWSIZE x COLSIZE
+   matrix.  Rather than use floats, we simply keep a single DENOMINATOR that
+   represents the denominator for every element in the matrix.  */
 typedef struct
 {
   lambda_matrix matrix;
@@ -46,7 +49,15 @@ typedef struct
 #define LTM_COLSIZE(T) ((T)->colsize)
 #define LTM_DENOMINATOR(T) ((T)->denominator)
 
-/* A vector representing a statement in the body of a loop.  */
+/* A vector representing a statement in the body of a loop.
+   The COEFFICIENTS vector contains a coefficient for each induction variable
+   in the loop nest containing the statement.
+   The DENOMINATOR represents the denominator for each coefficient in the
+   COEFFICIENT vector.
+
+   This structure is used during code generation in order to rewrite the old
+   induction variable uses in a statement in terms of the newly created
+   induction variables.  */
 typedef struct
 {
   lambda_vector coefficients;
@@ -57,7 +68,18 @@ typedef struct
 #define LBV_SIZE(T) ((T)->size)
 #define LBV_DENOMINATOR(T) ((T)->denominator)
 
-/* Piecewise linear expression.  */
+/* Piecewise linear expression.  
+   This structure represents a linear expression with terms for the invariants
+   and induction variables of a loop. 
+   COEFFICIENTS is a vector of coefficients for the induction variables, one
+   per loop in the loop nest.
+   CONSTANT is the constant portion of the linear expression
+   INVARIANT_COEFFICIENTS is a vector of coefficients for the loop invariants,
+   one per invariant.
+   DENOMINATOR is the denominator for all of the coefficients and constants in
+   the expression.  
+   The linear expressions can be linked together using the NEXT field, in
+   order to represent MAX or MIN of a group of linear expressions.  */
 typedef struct lambda_linear_expression_s
 {
   lambda_vector coefficients;
@@ -77,7 +99,12 @@ lambda_linear_expression lambda_linear_expression_new (int, int);
 void print_lambda_linear_expression (FILE *, lambda_linear_expression, int,
 				     int, char);
 
-/* Loop structure.  */
+/* Loop structure.  Our loop structure consists of a constant representing the
+   STEP of the loop, a set of linear expressions representing the LOWER_BOUND
+   of the loop, a set of linear expressions representing the UPPER_BOUND of
+   the loop, and a set of linear expressions representing the LINEAR_OFFSET of
+   the loop.  The linear offset is a set of linear expressions that are
+   applied to *both* the lower bound, and the upper bound.  */
 typedef struct lambda_loop_s
 {
   lambda_linear_expression lower_bound;
@@ -91,7 +118,12 @@ typedef struct lambda_loop_s
 #define LL_LINEAR_OFFSET(T) ((T)->linear_offset)
 #define LL_STEP(T)   ((T)->step)
 
-/* Loop nest structure.  */
+/* Loop nest structure.  
+   The loop nest structure consists of a set of loop structures (defined
+   above) in LOOPS, along with an integer representing the DEPTH of the loop,
+   and an integer representing the number of INVARIANTS in the loop.  Both of
+   these integers are used to size the associated coefficient vectors in the
+   linear expression structures.  */
 typedef struct
 {
   lambda_loop *loops;