From: Bernd Schmidt <bernds@codesourcery.com>
To: GCC Patches <gcc-patches@gcc.gnu.org>
Subject: [PATCH 5/6] Generate more shrink-wrapping opportunities
Date: Wed, 23 Mar 2011 14:56:00 -0000 [thread overview]
Message-ID: <4D8A09E5.7070105@codesourcery.com> (raw)
In-Reply-To: <4D8A0703.9090306@codesourcery.com>
[-- Attachment #1: Type: text/plain, Size: 485 bytes --]
The first basic block contains insns to move incoming argument registers
to pseudos. When these pseudos live across calls, they get allocated to
call-saved registers. This in turns disables shrink-wrapping, since the
move instruction requires the prologue (saving the call-saved reg) to
occur before it.
This patch addresses the problem by moving such moves downwards through
the CFG until we find a place where the destination is used or the
incoming argument is clobbered.
Bernd
[-- Attachment #2: enhance-sw.diff --]
[-- Type: text/plain, Size: 3775 bytes --]
* function.c (prepare_shrink_wrap): New function.
(thread_prologue_and_epilogue_insns): Call it.
Index: gcc/function.c
===================================================================
--- gcc.orig/function.c
+++ gcc/function.c
@@ -5299,6 +5299,127 @@ requires_stack_frame_p (rtx insn)
return true;
return false;
}
+
+/* Look for sets of call-saved registers in the first block of the
+ function, and move them down into successor blocks if the register
+ is used only on one path. This exposes more opportunities for
+ shrink-wrapping.
+ These kinds of sets often occur when incoming argument registers are
+ moved to call-saved registers because their values are live across
+ one or more calls during the function. */
+
+static void
+prepare_shrink_wrap (basic_block entry_block)
+{
+ rtx insn, curr;
+ FOR_BB_INSNS_SAFE (entry_block, insn, curr)
+ {
+ basic_block next_bb;
+ edge e, live_edge;
+ edge_iterator ei;
+ rtx set, scan;
+ unsigned destreg, srcreg;
+
+ if (!NONDEBUG_INSN_P (insn))
+ continue;
+ set = single_set (insn);
+ if (!set)
+ continue;
+
+ if (!REG_P (SET_SRC (set)) || !REG_P (SET_DEST (set)))
+ continue;
+ srcreg = REGNO (SET_SRC (set));
+ destreg = REGNO (SET_DEST (set));
+ if (hard_regno_nregs[srcreg][GET_MODE (SET_SRC (set))] > 1
+ || hard_regno_nregs[destreg][GET_MODE (SET_DEST (set))] > 1)
+ continue;
+
+ next_bb = entry_block;
+ scan = insn;
+
+ for (;;)
+ {
+ live_edge = NULL;
+ FOR_EACH_EDGE (e, ei, next_bb->succs)
+ {
+ if (REGNO_REG_SET_P (df_get_live_in (e->dest), destreg))
+ {
+ if (live_edge)
+ {
+ live_edge = NULL;
+ break;
+ }
+ live_edge = e;
+ }
+ }
+ if (!live_edge)
+ break;
+ /* We can sometimes encounter dead code. Don't try to move it
+ into the exit block. */
+ if (live_edge->dest == EXIT_BLOCK_PTR)
+ break;
+ if (EDGE_COUNT (live_edge->dest->preds) > 1)
+ break;
+ while (scan != BB_END (next_bb))
+ {
+ scan = NEXT_INSN (scan);
+ if (NONDEBUG_INSN_P (scan))
+ {
+ rtx link;
+ HARD_REG_SET set_regs;
+
+ CLEAR_HARD_REG_SET (set_regs);
+ note_stores (PATTERN (scan), record_hard_reg_sets,
+ &set_regs);
+ if (CALL_P (scan))
+ IOR_HARD_REG_SET (set_regs, call_used_reg_set);
+ for (link = REG_NOTES (scan); link; link = XEXP (link, 1))
+ if (REG_NOTE_KIND (link) == REG_INC)
+ record_hard_reg_sets (XEXP (link, 0), NULL, &set_regs);
+
+ if (TEST_HARD_REG_BIT (set_regs, srcreg)
+ || reg_referenced_p (SET_DEST (set),
+ PATTERN (scan)))
+ {
+ scan = NULL_RTX;
+ break;
+ }
+ if (CALL_P (scan))
+ {
+ rtx link = CALL_INSN_FUNCTION_USAGE (scan);
+ while (link)
+ {
+ rtx tmp = XEXP (link, 0);
+ if (GET_CODE (tmp) == USE
+ && reg_referenced_p (SET_DEST (set), tmp))
+ break;
+ link = XEXP (link, 1);
+ }
+ if (link)
+ {
+ scan = NULL_RTX;
+ break;
+ }
+ }
+ }
+ }
+ if (!scan)
+ break;
+ next_bb = live_edge->dest;
+ }
+
+ if (next_bb != entry_block)
+ {
+ rtx after = BB_HEAD (next_bb);
+ while (!NOTE_P (after)
+ || NOTE_KIND (after) != NOTE_INSN_BASIC_BLOCK)
+ after = NEXT_INSN (after);
+ emit_insn_after (PATTERN (insn), after);
+ delete_insn (insn);
+ }
+ }
+}
+
#endif
#ifdef HAVE_return
@@ -5499,6 +5620,8 @@ thread_prologue_and_epilogue_insns (void
bitmap_head bb_antic_flags;
bitmap_head bb_on_list;
+ prepare_shrink_wrap (entry_edge->dest);
+
bitmap_initialize (&bb_antic_flags, &bitmap_default_obstack);
bitmap_initialize (&bb_on_list, &bitmap_default_obstack);
next prev parent reply other threads:[~2011-03-23 14:56 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-23 14:44 Shrink-wrapping: Introduction Bernd Schmidt
2011-03-23 14:46 ` [PATCH 1/6] Disallow predicating the prologue Bernd Schmidt
2011-03-31 13:20 ` Jeff Law
2011-04-01 18:59 ` H.J. Lu
2011-04-01 21:08 ` Bernd Schmidt
2011-03-23 14:48 ` [PATCH 2/6] Unique return rtx Bernd Schmidt
2011-03-31 13:23 ` Jeff Law
2011-05-03 11:54 ` Bernd Schmidt
2011-03-23 14:51 ` [PATCH 3/6] Allow jumps in epilogues Bernd Schmidt
2011-03-23 16:46 ` Richard Henderson
2011-03-23 16:49 ` Bernd Schmidt
2011-03-23 17:19 ` Richard Henderson
2011-03-23 17:24 ` Bernd Schmidt
2011-03-23 17:27 ` Richard Henderson
2011-03-24 10:30 ` Bernd Schmidt
2011-03-25 17:51 ` Bernd Schmidt
2011-03-26 5:33 ` Richard Henderson
2011-03-31 20:09 ` Bernd Schmidt
2011-03-31 21:51 ` Richard Henderson
2011-03-31 22:36 ` Bernd Schmidt
2011-03-31 23:57 ` Richard Henderson
2011-04-05 21:59 ` Bernd Schmidt
2011-04-11 17:10 ` Richard Henderson
2011-04-13 14:16 ` Bernd Schmidt
2011-04-13 15:14 ` Bernd Schmidt
2011-04-13 15:16 ` Bernd Schmidt
2011-04-13 15:17 ` Bernd Schmidt
2011-04-13 15:28 ` Bernd Schmidt
2011-04-13 14:44 ` Richard Henderson
2011-04-13 14:54 ` Jakub Jelinek
2011-04-15 16:29 ` Bernd Schmidt
2011-03-23 14:56 ` Bernd Schmidt [this message]
2011-03-23 15:03 ` [PATCH 5/6] Generate more shrink-wrapping opportunities Jeff Law
2011-03-23 15:05 ` Bernd Schmidt
2011-03-23 15:18 ` Jeff Law
2011-03-31 13:26 ` Jeff Law
2011-03-31 13:34 ` Bernd Schmidt
2011-03-23 14:56 ` [PATCH 4/6] Shrink-wrapping Bernd Schmidt
2011-07-07 14:51 ` Richard Sandiford
2011-07-07 15:40 ` Bernd Schmidt
2011-07-07 17:00 ` Paul Koning
2011-07-07 17:02 ` Jeff Law
2011-07-07 17:05 ` Paul Koning
2011-07-07 17:08 ` Jeff Law
2011-07-07 17:30 ` Bernd Schmidt
2011-07-08 22:59 ` [pdp11] Emit prologue as rtl Richard Henderson
2011-07-09 13:46 ` Paul Koning
2011-07-09 16:53 ` Richard Henderson
2011-07-07 15:57 ` [PATCH 4/6] Shrink-wrapping Richard Earnshaw
2011-07-07 20:19 ` Richard Sandiford
2011-07-08 8:30 ` Richard Earnshaw
2011-07-08 13:57 ` Bernd Schmidt
2011-07-11 11:24 ` Richard Sandiford
2011-07-11 11:42 ` Bernd Schmidt
2011-07-21 3:57 ` Bernd Schmidt
2011-07-21 11:25 ` Richard Sandiford
2011-07-28 11:48 ` Bernd Schmidt
2011-07-28 12:45 ` Richard Sandiford
2011-07-28 23:30 ` Richard Earnshaw
2011-07-29 12:40 ` Bernd Schmidt
2011-08-03 10:42 ` Alan Modra
2011-08-03 11:19 ` Bernd Schmidt
2011-08-02 8:40 ` Bernd Schmidt
2011-08-03 15:39 ` Richard Sandiford
2011-08-24 19:23 ` Bernd Schmidt
2011-08-24 20:48 ` Richard Sandiford
2011-08-24 20:55 ` Bernd Schmidt
2011-08-26 14:49 ` Ramana Radhakrishnan
2011-08-26 14:58 ` Bernd Schmidt
2011-08-26 15:06 ` Ramana Radhakrishnan
2011-08-28 10:58 ` H.J. Lu
2011-07-07 21:41 ` Michael Hope
2011-03-23 14:57 ` [PATCH 6/6] A testcase Bernd Schmidt
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