diff options
Diffstat (limited to 'gcc/tree-data-ref.h')
| -rw-r--r-- | gcc/tree-data-ref.h | 56 |
1 files changed, 43 insertions, 13 deletions
diff --git a/gcc/tree-data-ref.h b/gcc/tree-data-ref.h index 7d6f9f94cb4..d80be31e3d0 100644 --- a/gcc/tree-data-ref.h +++ b/gcc/tree-data-ref.h @@ -24,25 +24,27 @@ Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA #include "lambda.h" -/** {base_address + offset + init} is the first location accessed by data-ref - in the loop, and step is the stride of data-ref in the loop in bytes; - e.g.: - +/* + The first location accessed by data-ref in the loop is the address of data-ref's + base (BASE_ADDRESS) plus the initial offset from the base. We divide the initial offset + into two parts: loop invariant offset (OFFSET) and constant offset (INIT). + STEP is the stride of data-ref in the loop in bytes. + Example 1 Example 2 data-ref a[j].b[i][j] a + x + 16B (a is int*) -First location info: + First location info: base_address &a a - offset j_0*D_j + i_0*D_i + C_a x - init C_b 16 + offset j_0*D_j + i_0*D_i x + init C_b + C_a 16 step D_j 4 access_fn NULL {16, +, 1} -Base object info: + Base object info: base_object a NULL access_fn <access_fns of indexes of b> NULL - **/ + */ struct first_location_in_loop { tree base_address; @@ -51,7 +53,6 @@ struct first_location_in_loop tree step; /* Access function related to first location in the loop. */ VEC(tree,heap) *access_fns; - }; struct base_object_info @@ -97,10 +98,39 @@ struct data_reference struct ptr_info_def *ptr_info; subvar_t subvars; - /* Alignment information. */ - /* The offset of the data-reference from its base in bytes. */ + /* Alignment information. + MISALIGNMENT is the offset of the data-reference from its base in bytes. + ALIGNED_TO is the maximum data-ref's alignment. + + Example 1, + for i + for (j = 3; j < N; j++) + a[j].b[i][j] = 0; + + For a[j].b[i][j], the offset from base (calculated in get_inner_reference() + will be 'i * C_i + j * C_j + C'. + We try to substitute the variables of the offset expression + with initial_condition of the corresponding access_fn in the loop. + 'i' cannot be substituted, since its access_fn in the inner loop is i. 'j' + will be substituted with 3. + + Example 2 + for (j = 3; j < N; j++) + a[j].b[5][j] = 0; + + Here the offset expression (j * C_j + C) will not contain variables after + subsitution of j=3 (3*C_j + C). + + Misalignment can be calculated only if all the variables can be + substituted with constants, otherwise, we record maximum possible alignment + in ALIGNED_TO. In Example 1, since 'i' cannot be substituted, + MISALIGNMENT will be NULL_TREE, and the biggest divider of C_i (a power of + 2) will be recorded in ALIGNED_TO. + + In Example 2, MISALIGNMENT will be the value of 3*C_j + C in bytes, and + ALIGNED_TO will be NULL_TREE. + */ tree misalignment; - /* The maximum data-ref's alignment. */ tree aligned_to; /* The type of the data-ref. */ |