When a @code{clobber} expression for a register appears inside a
@code{parallel} with other side effects, the register allocator
guarantees that the register is unoccupied both before and after that
-insn if the @samp{&} constraint is specified for at least one
-alternative (@pxref{Modifiers}) of the clobber. However, the reload
-phase may allocate a register used for one of the inputs unless the
-@samp{&} constraint is specified for the selected alternative. You
-can clobber either a specific hard register, a pseudo register, or a
-@code{scratch} expression; in the latter two cases, GCC will allocate
-a hard register that is available there for use as a temporary.
+insn. However, the reload phase may allocate a register used for one of
+the inputs unless the @samp{&} constraint is specified for the selected
+alternative (@pxref{Modifiers}). You can clobber either a specific hard
+register, a pseudo register, or a @code{scratch} expression; in the
+latter two cases, GCC will allocate a hard register that is available
+there for use as a temporary.
For instructions that require a temporary register, you should use
@code{scratch} instead of a pseudo-register because this will allow the
sparseset_clear_bit (allocnos_live, ALLOCNO_NUM (a));
}
-/* Mark the register REG as live. Store a 1 in hard_regs_live or
- allocnos_live for this register or the corresponding allocno,
- record how many consecutive hardware registers it actually
- needs. */
+/* Mark the register referenced by use or def REF as live
+ Store a 1 in hard_regs_live or allocnos_live for this register or
+ the corresponding allocno, record how many consecutive hardware
+ registers it actually needs. */
+
static void
-mark_reg_live (rtx reg)
+mark_ref_live (struct df_ref *ref)
{
+ rtx reg;
int regno;
+ reg = DF_REF_REG (ref);
+ if (GET_CODE (reg) == SUBREG)
+ reg = SUBREG_REG (reg);
gcc_assert (REG_P (reg));
regno = REGNO (reg);
}
}
-/* Mark the register referenced by use or def REF as live. */
-static void
-mark_ref_live (struct df_ref *ref)
+/* Return true if the definition described by DEF conflicts with the
+ instruction's inputs. */
+static bool
+def_conflicts_with_inputs_p (struct df_ref *def)
{
- rtx reg;
-
- reg = DF_REF_REG (ref);
- if (GET_CODE (reg) == SUBREG)
- reg = SUBREG_REG (reg);
- mark_reg_live (reg);
+ /* Conservatively assume that the condition is true for all clobbers. */
+ return DF_REF_FLAGS_IS_SET (def, DF_REF_MUST_CLOBBER);
}
-/* Mark the register REG as dead. Store a 0 in hard_regs_live or
+/* Mark the register referenced by definition DEF as dead, if the
+ definition is a total one. Store a 0 in hard_regs_live or
allocnos_live for the register. */
static void
-mark_reg_dead (rtx reg)
+mark_ref_dead (struct df_ref *def)
{
+ unsigned int i;
+ rtx reg;
int regno;
+ if (DF_REF_FLAGS_IS_SET (def, DF_REF_PARTIAL)
+ || DF_REF_FLAGS_IS_SET (def, DF_REF_CONDITIONAL))
+ return;
+
+ reg = DF_REF_REG (def);
+ if (GET_CODE (reg) == SUBREG)
+ reg = SUBREG_REG (reg);
gcc_assert (REG_P (reg));
regno = REGNO (reg);
}
else if (! TEST_HARD_REG_BIT (ira_no_alloc_regs, regno))
{
- unsigned int i;
int last = regno + hard_regno_nregs[regno][GET_MODE (reg)];
enum reg_class cover_class;
}
}
-/* Mark the register referenced by definition DEF as dead, if the
- definition is a total one. */
-static void
-mark_ref_dead (struct df_ref *def)
-{
- rtx reg;
-
- if (DF_REF_FLAGS_IS_SET (def, DF_REF_PARTIAL)
- || DF_REF_FLAGS_IS_SET (def, DF_REF_CONDITIONAL))
- return;
-
- reg = DF_REF_REG (def);
- if (GET_CODE (reg) == SUBREG)
- reg = SUBREG_REG (reg);
- mark_reg_dead (reg);
-}
-
-/* Mark early clobber registers of the current INSN as live (if
- LIVE_P) or dead. Return true if there are such registers. */
-static bool
-mark_early_clobbers (rtx insn, bool live_p)
-{
- int alt;
- int def;
- struct df_ref **def_rec;
- bool set_p = false;
- bool asm_p = asm_noperands (PATTERN (insn)) >= 0;
-
- if (asm_p)
- for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++)
- if (DF_REF_FLAGS_IS_SET (*def_rec, DF_REF_MUST_CLOBBER))
- {
- if (live_p)
- mark_ref_live (*def_rec);
- else
- mark_ref_dead (*def_rec);
- set_p = true;
- }
-
- for (def = 0; def < recog_data.n_operands; def++)
- {
- rtx dreg = recog_data.operand[def];
-
- if (GET_CODE (dreg) == SUBREG)
- dreg = SUBREG_REG (dreg);
- if (! REG_P (dreg))
- continue;
-
- for (alt = 0; alt < recog_data.n_alternatives; alt++)
- if ((recog_op_alt[def][alt].earlyclobber)
- && (recog_op_alt[def][alt].cl != NO_REGS))
- break;
-
- if (alt >= recog_data.n_alternatives)
- continue;
-
- if (live_p)
- mark_reg_live (dreg);
- else
- mark_reg_dead (dreg);
- set_p = true;
- }
- return set_p;
-}
-
/* Checks that CONSTRAINTS permits to use only one hard register. If
it is so, the function returns the class of the hard register.
Otherwise it returns NO_REGS. */
bitmap_iterator bi;
bitmap reg_live_out;
unsigned int px;
- bool set_p;
bb = loop_tree_node->bb;
if (bb != NULL)
}
extract_insn (insn);
- preprocess_constraints ();
process_single_reg_class_operands (false, freq);
/* See which defined values die here. */
for (use_rec = DF_INSN_USES (insn); *use_rec; use_rec++)
mark_ref_live (*use_rec);
- set_p = mark_early_clobbers (insn, true);
+ /* If any defined values conflict with the inputs, mark those
+ defined values as live. */
+ for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++)
+ if (def_conflicts_with_inputs_p (*def_rec))
+ mark_ref_live (*def_rec);
process_single_reg_class_operands (true, freq);
- if (set_p)
- mark_early_clobbers (insn, false);
+ /* See which of the defined values we marked as live are dead
+ before the instruction. */
+ for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++)
+ if (def_conflicts_with_inputs_p (*def_rec))
+ mark_ref_dead (*def_rec);
curr_point++;
}
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