On Thu, Dec 01, 2016 at 01:33:17PM +0100, Bernd Schmidt wrote:
> On 11/21/2016 01:36 PM, Dominik Vogt wrote:
> >diff --git a/gcc/combine.c b/gcc/combine.c
> >index b22a274..457fe8a 100644
> >--- a/gcc/combine.c
> >+++ b/gcc/combine.c
> >@@ -5575,10 +5575,23 @@ combine_simplify_rtx (rtx x, machine_mode op0_mode,
> >int in_dest,
> > {
> > rtx cop1 = const0_rtx;
> > enum rtx_code cond_code = simplify_comparison (NE, &cond, &cop1);
> >+ unsigned HOST_WIDE_INT nz;
> >
> > if (cond_code == NE && COMPARISON_P (cond))
> > return x;
> >
> >+ /* If the operation is an AND wrapped in a SIGN_EXTEND or ZERO_EXTEND
> >+ with either operand being just a constant single bit value, do
> >+ nothing since IF_THEN_ELSE is likely to increase the expression's
> >+ complexity. */
> >+ if (HWI_COMPUTABLE_MODE_P (mode)
> >+ && pow2p_hwi (nz = nonzero_bits (x, mode))
> >+ && ! ((code == SIGN_EXTEND || code == ZERO_EXTEND)
> >+ && GET_CODE (XEXP (x, 0)) == AND
> >+ && CONST_INT_P (XEXP (XEXP (x, 0), 0))
> >+ && UINTVAL (XEXP (XEXP (x, 0), 0)) == nz))
> >+ return x;
>
> It looks like this doesn't actually use cond or true/false_rtx. So
> this could be placed just above the call to if_then_else_cond to
> avoid unnecessary work. Ok if that works.
It does. Version 3 attached, bootstrapped on s390x and regression
tested on s390x biarch and s390.
Ciao
Dominik ^_^ ^_^
--
Dominik Vogt
IBM Germany
gcc/ChangeLog
* combine.c (combine_simplify_rtx): Suppress replacement of
"(and (reg) (const_int bit))" with "if_then_else".
>From 9202cab6332ce5dcfa740bbae3bcf07f3acc8705 Mon Sep 17 00:00:00 2001
From: Dominik Vogt <v...@linux.vnet.ibm.com>
Date: Mon, 31 Oct 2016 09:00:31 +0100
Subject: [PATCH] Do not simplify "(and (reg) (const bit)" to if_then_else.
combine_simplify_rtx() tries to replace rtx expressions with just two
possible values with an experession that uses if_then_else:
(if_then_else (condition) (value1) (value2))
If the original expression is e.g.
(and (reg) (const_int 2))
where the constant is the mask for a single bit, the replacement results
in a more complex expression than before:
(if_then_else (ne (zero_extract (reg) (1) (31))) (2) (0))
Similar replacements are done for
(signextend (and ...))
(zeroextend (and ...))
Suppress the replacement this special case in if_then_else_cond().
---
gcc/combine.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/gcc/combine.c b/gcc/combine.c
index a8dae89..52bde9e 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -5600,6 +5600,18 @@ combine_simplify_rtx (rtx x, machine_mode op0_mode, int
in_dest,
&& OBJECT_P (SUBREG_REG (XEXP (x, 0)))))))
{
rtx cond, true_rtx, false_rtx;
+ unsigned HOST_WIDE_INT nz;
+
+ /* If the operation is an AND wrapped in a SIGN_EXTEND or ZERO_EXTEND
with
+ either operand being just a constant single bit value, do nothing since
+ IF_THEN_ELSE is likely to increase the expression's complexity. */
+ if (HWI_COMPUTABLE_MODE_P (mode)
+ && pow2p_hwi (nz = nonzero_bits (x, mode))
+ && ! ((code == SIGN_EXTEND || code == ZERO_EXTEND)
+ && GET_CODE (XEXP (x, 0)) == AND
+ && CONST_INT_P (XEXP (XEXP (x, 0), 0))
+ && UINTVAL (XEXP (XEXP (x, 0), 0)) == nz))
+ return x;
cond = if_then_else_cond (x, &true_rtx, &false_rtx);
if (cond != 0
--
2.3.0
