compare-elim.c: Fix head comment.
* compare-elim.c: Fix head comment. (conforming_compare): Remove redundant test. (can_eliminate_compare): New function extracted from... (before_dom_children): ...here. Use it, replace direct uses of flag_non_call_exceptions and tidy up. (maybe_select_cc_mode): Tidy up. From-SVN: r218468
This commit is contained in:
Eric Botcazou
Eric Botcazou
parent
bbea402544
commit
6c6a593dc0
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@ -1,3 +1,12 @@
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2014-12-07 Eric Botcazou <ebotcazou@adacore.com>
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* compare-elim.c: Fix head comment.
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(conforming_compare): Remove redundant test.
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(can_eliminate_compare): New function extracted from...
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(before_dom_children): ...here. Use it, replace direct uses of
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flag_non_call_exceptions and tidy up.
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(maybe_select_cc_mode): Tidy up.
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2014-12-07 Felix Yang <felix.yang@huawei.com>
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Shanyao Chen <chenshanyao@huawei.com>
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@ -35,7 +35,7 @@ along with GCC; see the file COPYING3. If not see
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(1) All comparison patterns are represented as
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[(set (reg:CC) (compare:CC (reg) (immediate)))]
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[(set (reg:CC) (compare:CC (reg) (reg_or_immediate)))]
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(2) All insn patterns that modify the flags are represented as
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@ -157,7 +157,6 @@ conforming_compare (rtx_insn *insn)
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return NULL;
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if (REG_P (XEXP (src, 0))
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&& REG_P (XEXP (src, 0))
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&& (REG_P (XEXP (src, 1)) || CONSTANT_P (XEXP (src, 1))))
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return src;
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@ -266,6 +265,45 @@ public:
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virtual void before_dom_children (basic_block);
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};
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/* Return true if conforming COMPARE with EH_NOTE is redundant with comparison
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CMP and can thus be eliminated. */
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static bool
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can_eliminate_compare (rtx compare, rtx eh_note, struct comparison *cmp)
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{
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/* Take care that it's in the same EH region. */
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if (cfun->can_throw_non_call_exceptions
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&& !rtx_equal_p (eh_note, cmp->eh_note))
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return false;
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/* Make sure the compare is redundant with the previous. */
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if (!rtx_equal_p (XEXP (compare, 0), cmp->in_a)
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|| !rtx_equal_p (XEXP (compare, 1), cmp->in_b))
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return false;
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/* New mode must be compatible with the previous compare mode. */
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enum machine_mode new_mode
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= targetm.cc_modes_compatible (GET_MODE (compare), cmp->orig_mode);
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if (new_mode == VOIDmode)
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return false;
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if (cmp->orig_mode != new_mode)
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{
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/* Generate new comparison for substitution. */
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rtx flags = gen_rtx_REG (new_mode, targetm.flags_regnum);
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rtx x = gen_rtx_COMPARE (new_mode, cmp->in_a, cmp->in_b);
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x = gen_rtx_SET (VOIDmode, flags, x);
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if (!validate_change (cmp->insn, &PATTERN (cmp->insn), x, false))
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return false;
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cmp->orig_mode = new_mode;
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}
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return true;
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}
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/* Identify comparison instructions within BB. If the flags from the last
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compare in the BB is live at the end of the block, install the compare
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in BB->AUX. Called via dom_walker.walk (). */
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@ -317,62 +355,26 @@ find_comparison_dom_walker::before_dom_children (basic_block bb)
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src = conforming_compare (insn);
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if (src)
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{
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machine_mode src_mode = GET_MODE (src);
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rtx eh_note = NULL;
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if (flag_non_call_exceptions)
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if (cfun->can_throw_non_call_exceptions)
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eh_note = find_reg_note (insn, REG_EH_REGION, NULL);
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if (!last_cmp_valid)
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goto dont_delete;
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if (last_cmp_valid && can_eliminate_compare (src, eh_note, last_cmp))
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{
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if (eh_note)
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need_purge = true;
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delete_insn (insn);
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continue;
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}
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/* Take care that it's in the same EH region. */
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if (flag_non_call_exceptions
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&& !rtx_equal_p (eh_note, last_cmp->eh_note))
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goto dont_delete;
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/* Make sure the compare is redundant with the previous. */
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if (!rtx_equal_p (last_cmp->in_a, XEXP (src, 0))
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|| !rtx_equal_p (last_cmp->in_b, XEXP (src, 1)))
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goto dont_delete;
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/* New mode must be compatible with the previous compare mode. */
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{
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machine_mode new_mode
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= targetm.cc_modes_compatible (last_cmp->orig_mode, src_mode);
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if (new_mode == VOIDmode)
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goto dont_delete;
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if (new_mode != last_cmp->orig_mode)
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{
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rtx x, flags = gen_rtx_REG (src_mode, targetm.flags_regnum);
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/* Generate new comparison for substitution. */
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x = gen_rtx_COMPARE (new_mode, XEXP (src, 0), XEXP (src, 1));
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x = gen_rtx_SET (VOIDmode, flags, x);
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if (!validate_change (last_cmp->insn,
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&PATTERN (last_cmp->insn), x, false))
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goto dont_delete;
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last_cmp->orig_mode = new_mode;
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}
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}
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/* All tests and substitutions succeeded! */
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if (eh_note)
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need_purge = true;
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delete_insn (insn);
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continue;
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dont_delete:
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last_cmp = XCNEW (struct comparison);
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last_cmp->insn = insn;
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last_cmp->prev_clobber = last_clobber;
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last_cmp->in_a = XEXP (src, 0);
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last_cmp->in_b = XEXP (src, 1);
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last_cmp->eh_note = eh_note;
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last_cmp->orig_mode = src_mode;
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last_cmp->orig_mode = GET_MODE (src);
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all_compares.safe_push (last_cmp);
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/* It's unusual, but be prepared for comparison patterns that
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@ -391,7 +393,6 @@ find_comparison_dom_walker::before_dom_children (basic_block bb)
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/* In either case, the previous compare is no longer valid. */
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last_cmp = NULL;
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last_cmp_valid = false;
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continue;
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}
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/* Notice if this instruction uses the flags register. */
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@ -425,8 +426,7 @@ find_comparison_dom_walker::before_dom_children (basic_block bb)
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FOR_EACH_EDGE (e, ei, bb->succs)
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{
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basic_block dest = e->dest;
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if (bitmap_bit_p (df_get_live_in (bb),
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targetm.flags_regnum)
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if (bitmap_bit_p (df_get_live_in (bb), targetm.flags_regnum)
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&& !single_pred_p (dest))
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{
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last_cmp->missing_uses = true;
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@ -498,8 +498,7 @@ maybe_select_cc_mode (struct comparison *cmp, rtx a ATTRIBUTE_UNUSED,
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sel_mode = SELECT_CC_MODE (cmp->uses[0].code, a, b);
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for (i = 1; i < n; ++i)
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{
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machine_mode new_mode;
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new_mode = SELECT_CC_MODE (cmp->uses[i].code, a, b);
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machine_mode new_mode = SELECT_CC_MODE (cmp->uses[i].code, a, b);
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if (new_mode != sel_mode)
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{
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sel_mode = targetm.cc_modes_compatible (sel_mode, new_mode);
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@ -507,7 +506,7 @@ maybe_select_cc_mode (struct comparison *cmp, rtx a ATTRIBUTE_UNUSED,
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return NULL;
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}
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}
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if (sel_mode != cmp->orig_mode)
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{
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flags = gen_rtx_REG (sel_mode, targetm.flags_regnum);
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@ -633,7 +632,7 @@ try_eliminate_compare (struct comparison *cmp)
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validate_change (insn, &XVECEXP (PATTERN (insn), 0, 1), x, true);
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if (!apply_change_group ())
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return false;
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/* Success. Delete the compare insn... */
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delete_insn (cmp->insn);
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