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ggml-cpu: BMI2 is only available on amd64 #17528

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ggml-cpu: BMI2 is only available on amd64 #17528

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ggml-cpu: BMI2 is only available on amd64 
MSVC doesn't define __BMI2__ so it must be defined by by CMake. It was being set  whenever GGML_BMI2 is set, but that results in a failure (`error LNK2019: unresolved external symbol __pdep_u64`) when targeting x86 (aka 32 bit) Windows. The fix is to only set __BMI2__ when targeting amd64.
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@candrews
candrews authored Nov 26, 2025
commit 42f8fee633ce2188bb2d9189577e35b0fc2cea0e
5 changes: 4 additions & 1 deletion ggml/src/ggml-cpu/CMakeLists.txt
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Expand Up @@ -302,7 +302,10 @@ function(ggml_add_cpu_backend_variant_impl tag_name)
endif()
if (GGML_BMI2)
# MSVC does not define macro __BMI2__
list(APPEND ARCH_DEFINITIONS __BMI2__ GGML_BMI2)
if (${CMAKE_SYSTEM_PROCESSOR} MATCHES "amd64")
# BMI2 is only available on amd64
list(APPEND ARCH_DEFINITIONS __BMI2__ GGML_BMI2)
endif()
endif()
else ()
if (GGML_NATIVE)
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