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| author | Dominik Vogt <vogt@linux.vnet.ibm.com> | 2016-12-02 08:32:40 +0000 |
|---|---|---|
| committer | Andreas Krebbel <krebbel@gcc.gnu.org> | 2016-12-02 08:32:40 +0000 |
| commit | 32ff7e39c15206dada1406bdc06e18db9e02d248 (patch) | |
| tree | ddc0071ca81fc7ce09f2f6ea86ba05f4df56fc4b /gcc/combine.c | |
| parent | bba13c0c4359649687894823900e091576cbc2e6 (diff) | |
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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/ChangeLog:
2016-12-02 Dominik Vogt <vogt@linux.vnet.ibm.com>
* combine.c (combine_simplify_rtx): Suppress replacement of
"(and (reg) (const_int bit))" with "if_then_else".
From-SVN: r243162
Diffstat (limited to 'gcc/combine.c')
| -rw-r--r-- | gcc/combine.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/gcc/combine.c b/gcc/combine.c index b429453..7ba634a 100644 --- a/gcc/combine.c +++ b/gcc/combine.c @@ -5602,6 +5602,18 @@ 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 |