[Qemu-devel] [PATCH 0/2] Provide sextract32() and sextract64()

[Peter Maydell <peter.maydell@linaro.org>]

A common operation in instruction decoding is to take a field
from an instruction that represents a signed integer in some
arbitrary number of bits, and sign extend it into a C signed
integer type for manipulation. Provide new functions sextract32()
and sextract64() which perform this operation; they are like
the existing extract32() and extract64() except that the field
is sign-extended into the returned result.

I agree with Markus that sign-extending versions of our
extract functions are more flexible than the simple sext()
I proposed in an earlier RFC, hence the switch in this patch.
The other change is patch 2, which provides some simple test
cases. (Will be handy if we ever decide to revamp to avoid
the dependency on shift-left-signed behaviour.)

Peter Maydell (2):
  bitops: Provide sextract32() and sextract64()
  tests: Add test-bitops.c with some sextract tests

 include/qemu/bitops.h |   50 +++++++++++++++++++++++++++++++++
 tests/Makefile        |    2 ++
 tests/test-bitops.c   |   75 +++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 127 insertions(+)
 create mode 100644 tests/test-bitops.c

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1.7.9.5