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rs6000: Improve scc isel 

If we have a negative condition we can use a literal 0 in the isel,
instead of having to load it into a register.  If the condition is from
a comparison with an immediate we can change e.g. LT to LE and adjust
the immediate, saving a li instruction.


	* config/rs6000/rs6000.md (<code><GPR:mode><GPR2:mode>2_isel): Change
	LT/GT/LTU/GTU to LE/GE/LEU/GEU where possible.

From-SVN: r255186
This commit is contained in:
Segher Boessenkool 2017-11-28 01:17:16 +01:00 committed by Segher Boessenkool
parent 2ac1a8d832
commit fd8bf76c90
2 changed files with 37 additions and 4 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
2017-11-27 Segher Boessenkool <segher@kernel.crashing.org>
* config/rs6000/rs6000.md (<code><GPR:mode><GPR2:mode>2_isel): Change
LT/GT/LTU/GTU to LE/GE/LEU/GEU where possible.
2017-11-27 Michael Meissner <meissner@linux.vnet.ibm.com>
PR middle_end/82333

36
gcc/config/rs6000/rs6000.md
View File

@ -12333,8 +12333,34 @@
"&& 1"
[(pc)]
{
if (<CODE> == NE || <CODE> == LE || <CODE> == GE
|| <CODE> == LEU || <CODE> == GEU)
rtx_code code = <CODE>;
if (CONST_INT_P (operands[2]) && code != EQ && code != NE)
{
HOST_WIDE_INT val = INTVAL (operands[2]);
if (code == LT && val != -0x8000)
{
code = LE;
val--;
}
if (code == GT && val != 0x7fff)
{
code = GE;
val++;
}
if (code == LTU && val != 0)
{
code = LEU;
val--;
}
if (code == GTU && val != 0xffff)
{
code = GEU;
val++;
}
operands[2] = GEN_INT (val);
}
if (code == NE || code == LE || code == GE || code == LEU || code == GEU)
operands[3] = const0_rtx;
else
{
@ -12353,14 +12379,16 @@
rtx c1 = gen_rtx_COMPARE (<UNS>mode, operands[1], operands[2]);
emit_insn (gen_rtx_SET (operands[5], c1));
rtx c2 = gen_rtx_fmt_ee (<CODE>, <GPR:MODE>mode, operands[5], const0_rtx);
rtx c2 = gen_rtx_fmt_ee (code, <GPR:MODE>mode, operands[5], const0_rtx);
rtx x = gen_rtx_IF_THEN_ELSE (<GPR:MODE>mode, c2, operands[4], operands[3]);
emit_move_insn (operands[0], x);
DONE;
}
[(set (attr "cost")
(if_then_else (match_test "<CODE> == NE || <CODE> == LE || <CODE> == GE
(if_then_else (match_test "(CONST_INT_P (operands[2]) && <CODE> != EQ)
|| <CODE> == NE
|| <CODE> == LE || <CODE> == GE
|| <CODE> == LEU || <CODE> == GEU")
(const_string "9")
(const_string "10")))])