Merge tag 'pull-tcg-20230530' of https://gitlab.com/rth7680/qemu into staging

Improvements to 128-bit atomics:
  - Separate __int128_t type and arithmetic detection
  - Support 128-bit load/store in backend for i386, aarch64, ppc64, s390x
  - Accelerate atomics via host/include/
Decodetree:
  - Add named field syntax
  - Move tests to meson

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* tag 'pull-tcg-20230530' of https://gitlab.com/rth7680/qemu: (27 commits)
  tests/decode: Add tests for various named-field cases
  scripts/decodetree: Implement named field support
  scripts/decodetree: Implement a topological sort
  scripts/decodetree: Pass lvalue-formatter function to str_extract()
  docs: Document decodetree named field syntax
  tests/decode: Convert tests to meson
  decodetree: Do not remove output_file from /dev
  decodetree: Diagnose empty pattern group
  decodetree: Fix recursion in prop_format and build_tree
  decodetree: Add --test-for-error
  tcg: Remove TCG_TARGET_TLB_DISPLACEMENT_BITS
  accel/tcg: Add aarch64 store_atom_insert_al16
  accel/tcg: Add aarch64 lse2 load_atom_extract_al16_or_al8
  accel/tcg: Add x86_64 load_atom_extract_al16_or_al8
  accel/tcg: Extract store_atom_insert_al16 to host header
  accel/tcg: Extract load_atom_extract_al16_or_al8 to host header
  tcg/s390x: Support 128-bit load/store
  tcg/ppc: Support 128-bit load/store
  tcg/aarch64: Support 128-bit load/store
  tcg/aarch64: Simplify constraints on qemu_ld/st
  ...

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 28 insertions, 5 deletions

diff --git a/docs/devel/decodetree.rst b/docs/devel/decodetree.rst
index 49ea50c2a7..e3392aa705 100644
--- a/docs/devel/decodetree.rst
+++ b/docs/devel/decodetree.rst
@@ -23,22 +23,42 @@ Fields
 
 Syntax::
 
-  field_def     := '%' identifier ( unnamed_field )* ( !function=identifier )?
+  field_def     := '%' identifier ( field )* ( !function=identifier )?
+  field         := unnamed_field | named_field
   unnamed_field := number ':' ( 's' ) number
+  named_field   := identifier ':' ( 's' ) number
 
 For *unnamed_field*, the first number is the least-significant bit position
 of the field and the second number is the length of the field.  If the 's' is
-present, the field is considered signed.  If multiple ``unnamed_fields`` are
-present, they are concatenated.  In this way one can define disjoint fields.
+present, the field is considered signed.
+
+A *named_field* refers to some other field in the instruction pattern
+or format. Regardless of the length of the other field where it is
+defined, it will be inserted into this field with the specified
+signedness and bit width.
+
+Field definitions that involve loops (i.e. where a field is defined
+directly or indirectly in terms of itself) are errors.
+
+A format can include fields that refer to named fields that are
+defined in the instruction pattern(s) that use the format.
+Conversely, an instruction pattern can include fields that refer to
+named fields that are defined in the format it uses. However you
+cannot currently do both at once (i.e. pattern P uses format F; F has
+a field A that refers to a named field B that is defined in P, and P
+has a field C that refers to a named field D that is defined in F).
+
+If multiple ``fields`` are present, they are concatenated.
+In this way one can define disjoint fields.
 
 If ``!function`` is specified, the concatenated result is passed through the
 named function, taking and returning an integral value.
 
-One may use ``!function`` with zero ``unnamed_fields``.  This case is called
+One may use ``!function`` with zero ``fields``.  This case is called
 a *parameter*, and the named function is only passed the ``DisasContext``
 and returns an integral value extracted from there.
 
-A field with no ``unnamed_fields`` and no ``!function`` is in error.
+A field with no ``fields`` and no ``!function`` is in error.
 
 Field examples:
 
@@ -56,6 +76,9 @@ Field examples:
 | %shimm8 5:s8 13:1         | expand_shimm8(sextract(i, 5, 8) << 1 |      |
 |   !function=expand_shimm8 |               extract(i, 13, 1))            |
 +---------------------------+---------------------------------------------+
+| %sz_imm 10:2 sz:3         | expand_sz_imm(extract(i, 10, 2) << 3 |      |
+|   !function=expand_sz_imm |               extract(a->sz, 0, 3))         |
++---------------------------+---------------------------------------------+
 
 Argument Sets
 =============