On Tue, May 30, 2017 at 7:25 AM, Richard Sandiford
<richard.sandif...@linaro.org> wrote:
> Yuri Gribov <tetra2...@gmail.com> writes:
>> Added special case to build_range_check. Fixed couple of existing
>> tests where it changed codegen.
>>
>> -I
>>
>> From b7819f341e2ffa0437be497024f61d0a4e1be588 Mon Sep 17 00:00:00 2001
>> From: Yury Gribov <tetra2...@gmail.com>
>> Date: Fri, 26 May 2017 07:49:46 +0100
>> Subject: [PATCH 1/4] Generate bittests in range checks if possible.
>>
>> gcc/testsuite/
>> 2017-05-26 Yury Gribov <tetra2...@gmail.com>
>>
>> * c-c++-common/fold-masked-cmp-1.c: New test.
>> * c-c++-common/fold-masked-cmp-2.c: New test.
>> * gcc.dg/pr46309.c: Fix pattern.
>> * gcc.dg/pr46309-2.c: Fix pattern.
>>
>> gcc/
>> 2017-05-26 Yury Gribov <tetra2...@gmail.com>
>>
>> * fold-const.c (maskable_range_p): New function.
>> (build_range_check): Generate bittests if possible.
>> ---
>> gcc/fold-const.c | 41
>> ++++++++++++++++++++++++-
>> gcc/testsuite/c-c++-common/fold-masked-cmp-1.c | 41
>> +++++++++++++++++++++++++
>> gcc/testsuite/c-c++-common/fold-masked-cmp-2.c | 42
>> ++++++++++++++++++++++++++
>> gcc/testsuite/gcc.dg/pr46309-2.c | 2 +-
>> gcc/testsuite/gcc.dg/pr46309.c | 2 +-
>> 5 files changed, 125 insertions(+), 3 deletions(-)
>> create mode 100644 gcc/testsuite/c-c++-common/fold-masked-cmp-1.c
>> create mode 100644 gcc/testsuite/c-c++-common/fold-masked-cmp-2.c
>>
>> diff --git a/gcc/fold-const.c b/gcc/fold-const.c
>> index efc0b10..c334dc6 100644
>> --- a/gcc/fold-const.c
>> +++ b/gcc/fold-const.c
>> @@ -4745,6 +4745,38 @@ make_range (tree exp, int *pin_p, tree *plow, tree
>> *phigh,
>> *pin_p = in_p, *plow = low, *phigh = high;
>> return exp;
>> }
>> +
>> +/* Returns TRUE is [LOW, HIGH] range check can be optimized to
>
> s/is/if/
>
>> + a bitwise check i.e. when
>> + LOW == 0xXX...X00...0
>> + HIGH == 0xXX...X11...1
>> + Return corresponding mask in MASK and stem in VALUE. */
>> +
>> +static bool
>> +maskable_range_p (const_tree low, const_tree high, tree type, tree *mask,
>> tree *value)
>> +{
>> + if (TREE_CODE (low) != INTEGER_CST
>> + || TREE_CODE (high) != INTEGER_CST)
>> + return false;
>> +
>> + widest_int lo = wi::to_widest (low),
>> + hi = wi::to_widest (high);
>
> It shouldn't be necessary to go to widest here, since AIUI both
> values have the same type.Done. >> + widest_int end_mask = lo ^ hi, >> + stem_mask = ~end_mask; >> + if ((end_mask & (end_mask + 1)) != 0 >> + || (lo & end_mask) != 0) >> + return false; >> + >> + widest_int stem = lo & stem_mask; >> + if (stem != (hi & stem_mask)) >> + return false; > > FWIW, I think this is equivalent to: > > if (lo + (lo & -lo) != hi + 1) > return false; > > but I guess it's a matter of taste whether that's clearer or not. The change is cure but frankly I'd rather keep original version for the sake of readability... >> + *mask = wide_int_to_tree (type, stem_mask); >> + *value = wide_int_to_tree (type, stem); >> + >> + return true; I've attached an updated patch (rebased and retested on x64). Ok to commit? -Yury
0001-Generate-bittests-in-range-checks-if-possible.patch
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