[PATCH] Fixes -fsanitize=undefined warning about left-shifting a negative signed value.

[Artem Belevich]

Ping!

BTW, the issue the patch fixes is a ubsan warning in the following test
case:

test/ExecutionEngine/RuntimeDyld/AArch64/MachO_ARM64_relocations.s
/tmp/foo.o
third_party/llvm/llvm/lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldMachOAArch64.h:186:47:
runtime error: left shift of negative value -57344

--Artem

On Tue, Dec 23, 2014 at 1:02 PM, Artem Belevich <tra at google.com> wrote:
>
> ---
>  lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldMachOAArch64.h | 5
+++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git
a/lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldMachOAArch64.h
b/lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldMachOAArch64.h
> index 274c552..8fc58ee 100644
> --- a/lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldMachOAArch64.h
> +++ b/lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldMachOAArch64.h
> @@ -183,8 +183,9 @@ public:
>        assert(isInt<33>(Addend) && "Invalid page reloc value.");
>
>        // Encode the addend into the instruction.
> -      uint32_t ImmLoValue = (uint32_t)(Addend << 17) & 0x60000000;
> -      uint32_t ImmHiValue = (uint32_t)(Addend >> 9) & 0x00FFFFE0;
> +      uint64_t AddressBits = Addend & 0x1FFFFF000;
> +      uint32_t ImmLoValue = (uint32_t)(AddressBits << 17) & 0x60000000;
> +      uint32_t ImmHiValue = (uint32_t)(AddressBits >> 9) & 0x00FFFFE0;
>        *p = (*p & 0x9F00001F) | ImmHiValue | ImmLoValue;
>        break;
>      }
> --
> 2.2.0.rc0.207.ga3a616c
>



--
--Artem Belevich
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