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

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__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

Review-Url: https://codereview.chromium.org/2011073002
This commit is contained in:
mtklein 2016-06-23 11:20:58 -07:00 committed by Commit bot
parent 3e3c1a5857
commit 9834696ed8
1 changed files with 8 additions and 0 deletions
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8
gyp/dng_sdk.gyp
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@ -143,6 +143,14 @@
['skia_os != "linux"', {
'sources': ['<@(headers)'],
}],
['skia_arch_type == "arm" and skia_clang_build', {
# DNG SDK uses __builtin_smulll_overflow() to detect 64x64 bit multiply overflow.
# On ARMv7, Clang implements this with __mulodi4() in libclang_rt.
# I can't quite figure out how to link that here, so instead here's a shim for
# __builtin_smulll_overflow() that multiplies normally assuming no overflow.
# Tracked in b/29412086.
'defines': [ '__builtin_smulll_overflow(x,y,p)=(*(p)=(x)*(y), false)' ],
}],
],
'dependencies': [
'libjpeg-turbo-selector.gyp:libjpeg-turbo-selector',