Hello all,
This patch adds a target hook for disabling the eager delay slot filler which
when disabled can give better code. No new regressions. Ok to commit?
Thanks,
Simon
gcc/
* target.def (use_eager_delay_filler_p): New hook for selectively
disabling eager delay slot filler.
* reorg.c (dbr_schedule): Use the new hook.
* config/mips/mips.c (mips_use_eager_delay_filler_p): New static
function.
(TARGET_USE_EAGER_DELAY_FILLER_P): Define.
* doc/tm.texi.in: Add placeholder for new hook.
* doc/tm.texi: Regenerate.
gcc/testsuite/
* gcc.target/mips/ds-schedule-1.c: New file.
* gcc.target/mips/ds-schedule-2.c: Likewise.
Index: gcc/config/mips/mips.c
===================================================================
--- gcc/config/mips/mips.c (revision 227676)
+++ gcc/config/mips/mips.c (working copy)
@@ -14425,6 +14425,14 @@
return cached_can_issue_more;
}
+/* Implement USE_EAGER_DELAY_FILLER. */
+
+static bool
+mips_use_eager_delay_filler_p ()
+{
+ return TARGET_CB_NEVER;
+}
+
/* Update round-robin counters for ALU1/2 and FALU1/2. */
static void
@@ -19982,6 +19990,9 @@
#undef TARGET_IN_SMALL_DATA_P
#define TARGET_IN_SMALL_DATA_P mips_in_small_data_p
+#undef TARGET_USE_EAGER_DELAY_FILLER_P
+#define TARGET_USE_EAGER_DELAY_FILLER_P mips_use_eager_delay_filler_p
+
#undef TARGET_MACHINE_DEPENDENT_REORG
#define TARGET_MACHINE_DEPENDENT_REORG mips_reorg
Index: gcc/doc/tm.texi
===================================================================
--- gcc/doc/tm.texi (revision 227676)
+++ gcc/doc/tm.texi (working copy)
@@ -10949,6 +10949,15 @@
definition is null.
@end deftypefn
+@deftypefn {Target Hook} bool TARGET_USE_EAGER_DELAY_FILLER_P (void)
+This predicate controls the use of the eager delay slot filler. Targets
+such as certain MIPS architectures possess both branches with and without
+delay slots. As the eager delay slot filler can increase code size,
+disabling it is beneficial when ordinary branches are available. Use of
+delay slot branches filled using the basic filler is often still desirable
+as the delay slot can hide a pipeline bubble.
+@end deftypefn
+
@deftypefn {Target Hook} void TARGET_INIT_BUILTINS (void)
Define this hook if you have any machine-specific built-in functions
that need to be defined. It should be a function that performs the
Index: gcc/doc/tm.texi.in
===================================================================
--- gcc/doc/tm.texi.in (revision 227676)
+++ gcc/doc/tm.texi.in (working copy)
@@ -7985,6 +7985,8 @@
@hook TARGET_MACHINE_DEPENDENT_REORG
+@hook TARGET_USE_EAGER_DELAY_FILLER_P
+
@hook TARGET_INIT_BUILTINS
@hook TARGET_BUILTIN_DECL
Index: gcc/reorg.c
===================================================================
--- gcc/reorg.c (revision 227676)
+++ gcc/reorg.c (working copy)
@@ -3793,7 +3793,8 @@
{
fill_simple_delay_slots (1);
fill_simple_delay_slots (0);
- fill_eager_delay_slots ();
+ if (targetm.use_eager_delay_filler_p ())
+ fill_eager_delay_slots ();
relax_delay_slots (first);
}
Index: gcc/target.def
===================================================================
--- gcc/target.def (revision 227676)
+++ gcc/target.def (working copy)
@@ -3618,6 +3618,17 @@
definition is null.",
void, (void), NULL)
+/* Control of eager delay slot filling in delayed-branch scheduling. */
+DEFHOOK
+(use_eager_delay_filler_p,
+ "This predicate controls the use of the eager delay slot filler. Targets\n\
+such as certain MIPS architectures possess both branches with and without\n\
+delay slots. As the eager delay slot filler can increase code size,\n\
+disabling it is beneficial when ordinary branches are available. Use of\n\
+delay slot branches filled using the basic filler is often still desirable\n\
+as the delay slot can hide a pipeline bubble.", bool, (void),
+ hook_bool_void_true)
+
/* Create the __builtin_va_list type. */
DEFHOOK
(build_builtin_va_list,
Index: gcc/testsuite/gcc.target/mips/ds-schedule-1.c
===================================================================
--- gcc/testsuite/gcc.target/mips/ds-schedule-1.c (revision 0)
+++ gcc/testsuite/gcc.target/mips/ds-schedule-1.c (working copy)
@@ -0,0 +1,29 @@
+/* { dg-options "isa_rev>=6 -mcompact-branches=optimal -mno-abicalls -G4" } */
+/* { dg-final { scan-assembler-not "bne\t" } } */
+/* { dg-final { scan-assembler-not "beq\t" } } */
+/* { dg-final { scan-assembler-times "\\(foo\\)" 1 } } */
+
+/* Test that when compact branches are used, that a compact branch is
+ produced in the case where code expansion would have occurred if a
+ delay slot branch would have be used. 'foo' should only be
+ referenced once in the program text. */
+
+struct list
+{
+ struct list *next;
+ int element;
+};
+
+struct list *gr;
+
+int foo;
+
+extern void t (int, int, int*);
+
+void
+f (struct list **ptr)
+{
+ if (gr)
+ *ptr = gr->next;
+ t (1, foo, &gr->element);
+}
Index: gcc/testsuite/gcc.target/mips/ds-schedule-2.c
===================================================================
--- gcc/testsuite/gcc.target/mips/ds-schedule-2.c (revision 0)
+++ gcc/testsuite/gcc.target/mips/ds-schedule-2.c (working copy)
@@ -0,0 +1,28 @@
+/* { dg-options "-mcompact-branches=never -mno-abicalls -G4" } */
+/* { dg-skip-if "code quality test" { *-*-* } { "-O0" "-O1" "-Os" } { "" } } */
+/* { dg-final { scan-assembler "beq.*\n\tlw" } } */
+/* { dg-final { scan-assembler-times "\\(foo\\)" 2 } } */
+
+/* Test that when compact branches are explicitly disabled, that a non-compact
+ branch is produced. 'foo' should be referenced twice in the program text as
the
+ eager delay slot filler will duplicate the load of foo. */
+
+struct list
+{
+ struct list *next;
+ int element;
+};
+
+struct list *gr;
+
+int foo;
+
+extern void t (int, int, int*);
+
+void
+f (struct list **ptr)
+{
+ if (gr)
+ *ptr = gr->next;
+ t (1, foo, &gr->element);
+}
