diff options
Diffstat (limited to 'gcc/loop.c')
| -rw-r--r-- | gcc/loop.c | 20 |
1 files changed, 10 insertions, 10 deletions
@@ -22,8 +22,16 @@ Software Foundation, 59 Temple Place - Suite 330, Boston, MA /* This is the loop optimization pass of the compiler. It finds invariant computations within loops and moves them to the beginning of the loop. Then it identifies basic and - general induction variables. Strength reduction is applied to the general - induction variables, and induction variable elimination is applied to + general induction variables. + + Basic induction variables (BIVs) are a pseudo registers which are set within + a loop only by incrementing or decrementing its value. General induction + variables (GIVs) are pseudo registers with a value which is a linear function + of a basic induction variable. BIVs are recognized by `basic_induction_var'; + GIVs by `general_induction_var'. + + Once induction variables are identified, strength reduction is applied to the + general induction variables, and induction variable elimination is applied to the basic induction variables. It also finds cases where @@ -4223,14 +4231,6 @@ emit_prefetch_instructions (struct loop *loop) return; } -/* A "basic induction variable" or biv is a pseudo reg that is set - (within this loop) only by incrementing or decrementing it. */ -/* A "general induction variable" or giv is a pseudo reg whose - value is a linear function of a biv. */ - -/* Bivs are recognized by `basic_induction_var'; - Givs by `general_induction_var'. */ - /* Communication with routines called via `note_stores'. */ static rtx note_insn; |