* sched-int.h (ds_t, dw_t): Make unsigned int.

	Fix documentation that describes how all the ds_t bits are used.
	Reserve the last bit for delayed-branch scheduling.
	(BITS_PER_DEP_STATUS): Move to ds_t typedef.
	(BITS_PER_DEP_WEAK): Fix definition and documentation.
	(gen_dep_weak_1): Remove prototype.
	* sched-deps.c (get_dep_weak_1): Make static.
	* target.def (speculate_insn, needs_block_p, gen_spec_check,
	get_insn_spec_ds, get_insn_checked_ds): Adjust hook prototypes.
	* doc/tm.texi: Regenerate.
	* config/ia64/ia64.c (ia64_needs_block_p): Update prototype.



git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@199325 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 68 insertions, 34 deletions

diff --git a/gcc/sched-int.h b/gcc/sched-int.h
index 9ab33744780..90d5b05c75e 100644
--- a/gcc/sched-int.h
+++ b/gcc/sched-int.h
@@ -193,10 +193,11 @@ extern void sched_create_recovery_edges (basic_block, basic_block,
 extern state_t curr_state;
 
 /* Type to represent status of a dependence.  */
-typedef int ds_t;
+typedef unsigned int ds_t;
+#define BITS_PER_DEP_STATUS HOST_BITS_PER_INT
 
 /* Type to represent weakness of speculative dependence.  */
-typedef int dw_t;
+typedef unsigned int dw_t;
 
 extern enum reg_note ds_to_dk (ds_t);
 extern ds_t dk_to_ds (enum reg_note);
@@ -743,6 +744,7 @@ struct _haifa_deps_insn_data
   unsigned int cant_move : 1;
 };
 
+
 /* Bits used for storing values of the fields in the following
    structure.  */
 #define INCREASE_BITS 8
@@ -952,33 +954,53 @@ extern vec<haifa_deps_insn_data_def> h_d_i_d;
 #define IS_SPECULATION_BRANCHY_CHECK_P(INSN) \
   (RECOVERY_BLOCK (INSN) != NULL && RECOVERY_BLOCK (INSN) != EXIT_BLOCK_PTR)
 
-/* Dep status (aka ds_t) of the link encapsulates information, that is needed
-   for speculative scheduling.  Namely, it is 4 integers in the range
-   [0, MAX_DEP_WEAK] and 3 bits.
-   The integers correspond to the probability of the dependence to *not*
-   exist, it is the probability, that overcoming of this dependence will
-   not be followed by execution of the recovery code.  Nevertheless,
-   whatever high the probability of success is, recovery code should still
-   be generated to preserve semantics of the program.  To find a way to
-   get/set these integers, please refer to the {get, set}_dep_weak ()
-   functions in sched-deps.c .
-   The 3 bits in the DEP_STATUS correspond to 3 dependence types: true-,
-   output- and anti- dependence.  It is not enough for speculative scheduling
-   to know just the major type of all the dependence between two instructions,
-   as only true dependence can be overcome.
-   There also is the 4-th bit in the DEP_STATUS (HARD_DEP), that is reserved
-   for using to describe instruction's status.  It is set whenever instruction
-   has at least one dependence, that cannot be overcame.
-   See also: check_dep_status () in sched-deps.c .  */
+
+/* Dep status (aka ds_t) of the link encapsulates all information for a given
+   dependency, including everything that is needed for speculative scheduling.
+
+   The lay-out of a ds_t is as follows:
+
+   1. Integers corresponding to the probability of the dependence to *not*
+      exist.  This is the probability that overcoming this dependence will
+      not be followed by execution of the recovery code.  Note that however
+      high this probability is, the recovery code should still always be
+      generated to preserve semantics of the program.
+
+      The probability values can be set or retrieved using the functions
+      the set_dep_weak() and get_dep_weak() in sched-deps.c.  The values
+      are always in the range [0, MAX_DEP_WEAK].
+
+	BEGIN_DATA	: BITS_PER_DEP_WEAK
+	BE_IN_DATA	: BITS_PER_DEP_WEAK
+	BEGIN_CONTROL	: BITS_PER_DEP_WEAK
+	BE_IN_CONTROL	: BITS_PER_DEP_WEAK
+
+      The basic type of DS_T is a host int.  For a 32-bits int, the values
+      will each take 6 bits.
 
-/* We exclude sign bit.  */
-#define BITS_PER_DEP_STATUS (HOST_BITS_PER_INT - 1)
+   2. The type of dependence.  This supercedes the old-style REG_NOTE_KIND
+      values.  TODO: Use this field instead of DEP_TYPE, or make DEP_TYPE
+      extract the dependence type from here.
 
-/* First '6' stands for 4 dep type bits and the HARD_DEP and DEP_CANCELLED
-   bits.
-   Second '4' stands for BEGIN_{DATA, CONTROL}, BE_IN_{DATA, CONTROL}
-   dep weakness.  */
-#define BITS_PER_DEP_WEAK ((BITS_PER_DEP_STATUS - 6) / 4)
+	dep_type	:  4 => DEP_{TRUE|OUTPUT|ANTI|CONTROL}
+
+   3. Various flags:
+
+	HARD_DEP	:  1 =>	Set if an instruction has a non-speculative
+				dependence.  This is an instruction property
+				so this bit can only appear in the TODO_SPEC
+				field of an instruction.
+	DEP_POSTPONED	:  1 =>	Like HARD_DEP, but the hard dependence may
+				still be broken by adjusting the instruction.
+	DEP_CANCELLED	:  1 =>	Set if a dependency has been broken using
+				some form of speculation.
+	RESERVED	:  1 => Reserved for use in the delay slot scheduler.
+
+   See also: check_dep_status () in sched-deps.c .  */
+
+/* The number of bits per weakness probability.  There are 4 weakness types
+   and we need 8 bits for other data in a DS_T.  */
+#define BITS_PER_DEP_WEAK ((BITS_PER_DEP_STATUS - 8) / 4)
 
 /* Mask of speculative weakness in dep_status.  */
 #define DEP_WEAK_MASK ((1 << BITS_PER_DEP_WEAK) - 1)
@@ -996,7 +1018,9 @@ extern vec<haifa_deps_insn_data_def> h_d_i_d;
 #define MIN_DEP_WEAK 1
 
 /* This constant represents 100% probability.
-   E.g. it is used to represent weakness of dependence, that doesn't exist.  */
+   E.g. it is used to represent weakness of dependence, that doesn't exist.
+   This value never appears in a ds_t, it is only used for computing the
+   weakness of a dependence.  */
 #define NO_DEP_WEAK (MAX_DEP_WEAK + MIN_DEP_WEAK)
 
 /* Default weakness of speculative dependence.  Used when we can't say
@@ -1011,8 +1035,10 @@ enum SPEC_TYPES_OFFSETS {
   BE_IN_CONTROL_BITS_OFFSET = BEGIN_CONTROL_BITS_OFFSET + BITS_PER_DEP_WEAK
 };
 
-/* The following defines provide numerous constants used to distinguish between
-   different types of speculative dependencies.  */
+/* The following defines provide numerous constants used to distinguish
+   between different types of speculative dependencies.  They are also
+   used as masks to clear/preserve the bits corresponding to the type
+   of dependency weakness.  */
 
 /* Dependence can be overcome with generation of new data speculative
    instruction.  */
@@ -1058,15 +1084,24 @@ enum SPEC_TYPES_OFFSETS {
 
 /* Instruction has non-speculative dependence.  This bit represents the
    property of an instruction - not the one of a dependence.
-   Therefore, it can appear only in TODO_SPEC field of an instruction.  */
+   Therefore, it can appear only in the TODO_SPEC field of an instruction.  */
 #define HARD_DEP (DEP_CONTROL << 1)
 
-/* Set in the TODO_SPEC field of an instruction for which new_ready
-   has decided not to schedule it speculatively.  */
+/* Like HARD_DEP, but dependencies can perhaps be broken by modifying
+   the instructions.  This is used for example to change:
+
+   rn++		=>	rm=[rn + 4]
+   rm=[rn]		rn++
+
+   For instructions that have this bit set, one of the dependencies of
+   the instructions will have a non-NULL REPLACE field in its DEP_T.
+   Just like HARD_DEP, this bit is only ever set in TODO_SPEC.  */
 #define DEP_POSTPONED (HARD_DEP << 1)
 
+/* Set if a dependency is cancelled via speculation.  */
 #define DEP_CANCELLED (DEP_POSTPONED << 1)
 
+
 /* This represents the results of calling sched-deps.c functions,
    which modify dependencies.  */
 enum DEPS_ADJUST_RESULT {
@@ -1268,7 +1303,6 @@ extern void deps_analyze_insn (struct deps_desc *, rtx);
 extern void remove_from_deps (struct deps_desc *, rtx);
 extern void init_insn_reg_pressure_info (rtx);
 
-extern dw_t get_dep_weak_1 (ds_t, ds_t);
 extern dw_t get_dep_weak (ds_t, ds_t);
 extern ds_t set_dep_weak (ds_t, ds_t, dw_t);
 extern dw_t estimate_dep_weak (rtx, rtx);