| Message ID | 1312385438-6273-2-git-send-email-amonakov@ispras.ru |
|---|---|
| State | New |
| Headers | show |
On 08/03/2011 11:30 AM, Alexander Monakov wrote: > From: Dmitry Melnik<dm@ispras.ru> > > EXPR_SPEC is an indicator of the speculativeness of an expression (an > instruction or just an rhs), as it is incremented each time the expression is > moved up across a conditional branch. When merging expr attributes for > similar exprs available from two destinations of a branch, sel-sched assigns > the minimum of EXPR_SPEC's to the result, effectively making the resulting > expr non-speculative if only one of those exprs was non-speculative. However, > since we are relying on EXPR_SPEC being a correct indication of expr's > speculativeness when deciding whether it would need a bookkeeping copy, we > really want to avoid that. > > The patch changes minimum to maximum, making the code match what was > originally intended. > > 2011-08-04 Dmitry Melnik<dm@ispras.ru> > > * sel-sched-ir.c (merge_expr_data): Take maximum spec. OK, thanks.
diff --git a/gcc/sel-sched-ir.c b/gcc/sel-sched-ir.c index de7629a..5a287d0 100644 --- a/gcc/sel-sched-ir.c +++ b/gcc/sel-sched-ir.c @@ -1810,9 +1810,9 @@ update_speculative_bits (expr_t to, expr_t from, insn_t split_point) void merge_expr_data (expr_t to, expr_t from, insn_t split_point) { - /* For now, we just set the spec of resulting expr to be minimum of the specs - of merged exprs. */ - if (EXPR_SPEC (to) > EXPR_SPEC (from)) + /* Choose the maximum of the specs of merged exprs. This is required + for correctness of bookkeeping. */ + if (EXPR_SPEC (to) < EXPR_SPEC (from)) EXPR_SPEC (to) = EXPR_SPEC (from); if (split_point)
From: Dmitry Melnik <dm@ispras.ru> EXPR_SPEC is an indicator of the speculativeness of an expression (an instruction or just an rhs), as it is incremented each time the expression is moved up across a conditional branch. When merging expr attributes for similar exprs available from two destinations of a branch, sel-sched assigns the minimum of EXPR_SPEC's to the result, effectively making the resulting expr non-speculative if only one of those exprs was non-speculative. However, since we are relying on EXPR_SPEC being a correct indication of expr's speculativeness when deciding whether it would need a bookkeeping copy, we really want to avoid that. The patch changes minimum to maximum, making the code match what was originally intended. 2011-08-04 Dmitry Melnik <dm@ispras.ru> * sel-sched-ir.c (merge_expr_data): Take maximum spec.