diff options
Diffstat (limited to 'gcc/lambda-code.c')
| -rw-r--r-- | gcc/lambda-code.c | 22 |
1 files changed, 18 insertions, 4 deletions
diff --git a/gcc/lambda-code.c b/gcc/lambda-code.c index d564f43..0d066b9 100644 --- a/gcc/lambda-code.c +++ b/gcc/lambda-code.c @@ -651,7 +651,19 @@ compute_nest_using_fourier_motzkin (int size, } /* Compute the loop bounds for the auxiliary space NEST. - Input system used is Ax <= b. TRANS is the unimodular transformation. */ + Input system used is Ax <= b. TRANS is the unimodular transformation. + Given the original nest, this function will + 1. Convert the nest into matrix form, which consists of a matrix for the + coefficients, a matrix for the + invariant coefficients, and a vector for the constants. + 2. Use the matrix form to calculate the lattice base for the nest (which is + a dense space) + 3. Compose the dense space transform with the user specified transform, to + get a transform we can easily calculate transformed bounds for. + 4. Multiply the composed transformation matrix times the matrix form of the + loop. + 5. Transform the newly created matrix (from step 4) back into a loop nest + using fourier motzkin elimination to figure out the bounds. */ static lambda_loopnest lambda_compute_auxillary_space (lambda_loopnest nest, @@ -786,9 +798,11 @@ lambda_compute_auxillary_space (lambda_loopnest nest, } /* Compute the loop bounds for the target space, using the bounds of - the auxiliary nest AUXILLARY_NEST, and the triangular matrix H. This is - done by matrix multiplication and then transformation of the new matrix - back into linear expression form. + the auxiliary nest AUXILLARY_NEST, and the triangular matrix H. + The target space loop bounds are computed by multiplying the triangular + matrix H by the auxillary nest, to get the new loop bounds. The sign of + the loop steps (positive or negative) is then used to swap the bounds if + the loop counts downwards. Return the target loopnest. */ static lambda_loopnest |