tcg: Allow top bit of SIMD_DATA_BITS to be set in simd_desc()

tcg: Allow top bit of SIMD_DATA_BITS to be set in simd_desc()

In simd_desc() we create a SIMD descriptor from various pieces
including an arbitrary data value from the caller.  We try to
sanitize these to make sure everything will fit: the 'data' value
needs to fit in the SIMD_DATA_BITS (== 22) sized field.  However we
do that sanitizing with:
   tcg_debug_assert(data == sextract32(data, 0, SIMD_DATA_BITS));

This works for the case where the data is supposed to be considered
as a signed integer (which can then be returned via simd_data()).
However, some callers want to treat the data value as unsigned.

Specifically, for the Arm SVE operations, make_svemte_desc()
assembles a data value as a collection of fields, and it needs to use
all 22 bits.  Currently if MTE is enabled then its MTEDESC SIZEM1
field may have the most significant bit set, and then it will trip
this assertion.

Loosen the assertion so that we only check that the data value will
fit into the field in some way, either as a signed or as an unsigned
value.  This means we will fail to detect some kinds of bug in the
callers, but we won't spuriously assert for intentional use of the
data field as unsigned.

Cc: qemu-stable@nongnu.org
Fixes: db432672dc50e ("tcg: Add generic vector expanders")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2601
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-ID: <20241115172515.1229393-1-peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
(cherry picked from commit 8377e3fb854d126ba10e61cb6b60885af8443ad4)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>