Work around missing __mulodi4() on ARMv7 + Clang builds.

Work around missing __mulodi4() on ARMv7 + Clang builds.

__mulodi4() is roughly,

    int64_t __mulodi4(int64_t a, int64_t b, int* overflow) {
        int64_t result = a*b;
        *overflow = did_overflow(result);
        return result;
    }

It's used by Clang's __builtin_smulll_overflow(), which is basically the same
except it swaps the positions of the return value and the out parameter.

DNG SDK in turn uses __builtin_smulll_overflow().

When building ARMv7 binaries with Clang, __mulodi4() turns up as a missing symbol.
That's because it's defined in a separate compiler-rt library.  I have not been
able to link that.  Instead, I've provided our own trivial __builtin_smulll_overflow().


Before this patch both nanobench and DM failed dynamically linking __mulodi4().  After this patch nanobench runs for a while, eventually segfaulting.  DM immediately segfaults.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2011073002

Committed: https://skia.googlesource.com/skia/+/9834696ed8bda2c1a5009b07e9092428cc1cd7bc

[mtklein_C, 2016-05-26 18:07:19]

Description was changed from

==========
Work around missing __mulodi4() on ARMv7 + Clang builds.

__mulodi4() is roughly,

    int64_t __mulodi4(int64_t a, int64_t b, int* overflow) {
        int64_t result = a*b;
        *overflow = did_overflow(result);
        return result;
    }

It's used by Clang's __builtin_smulll_overflow(), which is basically the same
except it swaps the positions of the return value and the out parameter.

DNG SDK in turn uses __builtin_smulll_overflow().

When building ARMv7 binaries with Clang, __mulodi4() turns up as a missing
symbol.
That's because it's defined in a separate compiler-rt library.  I have not been
able to link that.  Instead, I've provided our own trivial
__builtin_smulll_overflow().

BUG=skia:
==========

to

==========
Work around missing __mulodi4() on ARMv7 + Clang builds.

__mulodi4() is roughly,

    int64_t __mulodi4(int64_t a, int64_t b, int* overflow) {
        int64_t result = a*b;
        *overflow = did_overflow(result);
        return result;
    }

It's used by Clang's __builtin_smulll_overflow(), which is basically the same
except it swaps the positions of the return value and the out parameter.

DNG SDK in turn uses __builtin_smulll_overflow().

When building ARMv7 binaries with Clang, __mulodi4() turns up as a missing
symbol.
That's because it's defined in a separate compiler-rt library.  I have not been
able to link that.  Instead, I've provided our own trivial
__builtin_smulll_overflow().

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2011073002
==========

[mtklein, 2016-05-26 18:09:28]

Description was changed from

==========
Work around missing __mulodi4() on ARMv7 + Clang builds.

__mulodi4() is roughly,

    int64_t __mulodi4(int64_t a, int64_t b, int* overflow) {
        int64_t result = a*b;
        *overflow = did_overflow(result);
        return result;
    }

It's used by Clang's __builtin_smulll_overflow(), which is basically the same
except it swaps the positions of the return value and the out parameter.

DNG SDK in turn uses __builtin_smulll_overflow().

When building ARMv7 binaries with Clang, __mulodi4() turns up as a missing
symbol.
That's because it's defined in a separate compiler-rt library.  I have not been
able to link that.  Instead, I've provided our own trivial
__builtin_smulll_overflow().

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2011073002
==========

to

==========
Work around missing __mulodi4() on ARMv7 + Clang builds.

__mulodi4() is roughly,

    int64_t __mulodi4(int64_t a, int64_t b, int* overflow) {
        int64_t result = a*b;
        *overflow = did_overflow(result);
        return result;
    }

It's used by Clang's __builtin_smulll_overflow(), which is basically the same
except it swaps the positions of the return value and the out parameter.

DNG SDK in turn uses __builtin_smulll_overflow().

When building ARMv7 binaries with Clang, __mulodi4() turns up as a missing
symbol.
That's because it's defined in a separate compiler-rt library.  I have not been
able to link that.  Instead, I've provided our own trivial
__builtin_smulll_overflow().


Before this patch both nanobench and DM failed dynamically linking __mulodi4(). 
After this patch nanobench runs for a while, eventually segfaulting.  DM
immediately segfaults.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2011073002
==========

[mtklein_C, 2016-05-26 18:10:41]

mtklein@chromium.org changed reviewers:
+ djsollen@google.com

[mtklein_C, 2016-05-26 18:10:49]

The CQ bit was checked by mtklein@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-05-26 18:10:58]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2011073002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/2011073002/20001

[commit-bot: I haz the power, 2016-05-26 18:25:28]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-05-26 18:25:29]

Dry run: This issue passed the CQ dry run.

[commit-bot: I haz the power, 2016-05-26 18:25:37]

Dry run: None

[djsollen, 2016-06-23 17:42:49]

can you note in the comments that this is being tracked in b/29412086?  Other
than that it lgtm

[mtklein, 2016-06-23 17:45:46]

The CQ bit was checked by mtklein@google.com

[mtklein, 2016-06-23 17:45:47]

The patchset sent to the CQ was uploaded after l-g-t-m from djsollen@google.com
Link to the patchset: https://codereview.chromium.org/2011073002/#ps40001
(title: "add bug note")

[commit-bot: I haz the power, 2016-06-23 17:45:54]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2011073002/40001

[commit-bot: I haz the power, 2016-06-23 18:21:01]

Description was changed from

==========
Work around missing __mulodi4() on ARMv7 + Clang builds.

__mulodi4() is roughly,

    int64_t __mulodi4(int64_t a, int64_t b, int* overflow) {
        int64_t result = a*b;
        *overflow = did_overflow(result);
        return result;
    }

It's used by Clang's __builtin_smulll_overflow(), which is basically the same
except it swaps the positions of the return value and the out parameter.

DNG SDK in turn uses __builtin_smulll_overflow().

When building ARMv7 binaries with Clang, __mulodi4() turns up as a missing
symbol.
That's because it's defined in a separate compiler-rt library.  I have not been
able to link that.  Instead, I've provided our own trivial
__builtin_smulll_overflow().


Before this patch both nanobench and DM failed dynamically linking __mulodi4(). 
After this patch nanobench runs for a while, eventually segfaulting.  DM
immediately segfaults.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2011073002
==========

to

==========
Work around missing __mulodi4() on ARMv7 + Clang builds.

__mulodi4() is roughly,

    int64_t __mulodi4(int64_t a, int64_t b, int* overflow) {
        int64_t result = a*b;
        *overflow = did_overflow(result);
        return result;
    }

It's used by Clang's __builtin_smulll_overflow(), which is basically the same
except it swaps the positions of the return value and the out parameter.

DNG SDK in turn uses __builtin_smulll_overflow().

When building ARMv7 binaries with Clang, __mulodi4() turns up as a missing
symbol.
That's because it's defined in a separate compiler-rt library.  I have not been
able to link that.  Instead, I've provided our own trivial
__builtin_smulll_overflow().


Before this patch both nanobench and DM failed dynamically linking __mulodi4(). 
After this patch nanobench runs for a while, eventually segfaulting.  DM
immediately segfaults.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2011073002

Committed:
https://skia.googlesource.com/skia/+/9834696ed8bda2c1a5009b07e9092428cc1cd7bc
==========

[commit-bot: I haz the power, 2016-06-23 18:21:02]

Committed patchset #3 (id:40001) as
https://skia.googlesource.com/skia/+/9834696ed8bda2c1a5009b07e9092428cc1cd7bc