| Commit message (Collapse) | Author | Age | Files | Lines |
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This big PR adds support for bit fields in structs and unions to
the verified part of CompCert, namely the CompCert C and Clight
languages.
The compilation of bit field accesses to normal integer accesses +
shifts and masks is done and proved correct as part of the Cshmgen
pass.
The layout of bit fields in memory is done by the functions in module
Ctypes. It follows the ELF ABI layout algorithm. As a bonus, basic
soundness properties of the layout are shown, such as "two different
bit fields do not overlap" or "a bit field and a regular field do not
overlap".
All this replaces the previous emulation of bit fields by
source-to-source rewriting in the unverified front-end of CompCert
(module cparse/Bitfield.ml). This emulation was prone to errors (see
nonstandard layout instead.
The core idea for the PR is that expressions in l-value position
denote not just a block, a byte offset and a type, but also a bitfield
designator saying whether all the bits of the type are accessed
(designator Full) or only some of its bits (designator
Bits). Designators of the Bits kind appear when the l-value is a bit
field access; the bit width and bit offset in Bits are computed by the
functions in Ctypes that implement the layout algorithm.
Consequently, both in the semantics of CompCert C and Clight and in
the SimplExpr, SimplLocals and Cshmgen compilation passes, pairs of a
type and a bitfield designator are used in a number of places where a
single type was used before.
The introduction of bit fields has a big impact on static
initialization (module cfrontend/Initializers.v), which had to be
rewritten in large part, along with its soundness proof
(cfrontend/Initializersproof.v).
Both static initialization and run-time manipulation of bit fields are
tested in test/abi using differential testing against GCC and
randomly-generated structs.
This work exposed subtle interactions between bit fields and the
volatile modifier. Currently, the volatile modifier is ignored when
accessing a bit field (and a warning is printed at compile-time), just
like it is ignored when accessing a struct or union as a r-value.
Currently, the natural alignment of bit fields and their storage units
cannot be modified with the aligned attribute. _Alignas on bit fields
is rejected as per C11, and the packed modifier cannot be applied to a
struct containing bit fields.
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The GPL makes sense for whole applications, but the dual-licensed Coq
and OCaml files are more like libraries to be combined with other
code, so the LGPL is more appropriate.
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Since Coq 8.12, `omega` is flagged as deprecated and scheduled for removal.
Also replace CompCert's homemade tactics `omegaContradiction`, `xomega`,
and `xomegaContradiction` with `lia` and `extlia`.
Turn back on the deprecation warning for uses of `omega`.
Make the proof of `Ctypes.sizeof_pos` more robust to variations in `lia`.
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"Hint Resolve foo." becomes "Hint Resolve foo : core", or
"Local Hint Resolve foo : core".
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This will soon be deprecated by Coq.
Manual merge of pull request #224 by vbgl. Closes: #224
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- Introduce Archi.ptr64 parameter.
- Define module Ptrofs of integers as wide as a pointer (64 if Archi.ptr64, 32 otherwise).
- Use Ptrofs.int as the offset type for Vptr values and anywhere pointer offsets are manipulated.
- Modify Val operations that handle pointers (e.g. Val.add, Val.sub, Val.cmpu) so that in 64-bit pointer mode it is the "long" operation (e.g. Val.addl, Val.subl, Val.cmplu) that handles pointers.
- Update the memory model accordingly.
- Modify C operations that handle pointers (e.g. addition, subtraction, comparisons) accordingly.
- Make it possible to turn off the splitting of 64-bit integers into pairs of 32-bit integers.
- Update the compiler front-end and back-end accordingly.
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Manual merging of branch jhjourdan:coq8.5.
No other change un functionality.
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In compCert 2.5 the semantics of pointer comparisons against the NULL pointer was made more accurate by making it undefined if the pointer is invalid (outside bounds). Technical difficulties prevented this change from being propagated to the semantics of casts from pointer types to the _Bool type, which involves an implicit pointer comparison against NULL. Hence, this kind of casts was temporarily given undefined semantics.
This commit makes pointer-to-_Bool casts semantically defined (again), provided the pointer is valid. This reinstates the equivalence between casts to _Bool and comparisons != 0. The technical difficulties mentioned above came from the translation of assignments in a value context in the SimplExpr pass. The pass was lightly modified to work around the issue.
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The previous translation (in SimplExpr) produced references to the
same temporary variable with two different types (bool and int),
which is not nice if we want to typecheck the generated Clight.
The new translation avoids this and also gets rid of the double
cast to bool then to int. The trick is to change Eparen
(in CompCert C expressions) to take two types: the type to which the
argument must be converted, and the type with which the resulting
expression is seen.
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(in CompCert C to Cminor, included)
- Translation of "switch" to decision trees or jumptables made generic
over the sizes of integers and moved to the Cminor->CminorSel pass
instead of CminorSel->RTL as before.
- CminorSel: add "exitexpr" to support the above.
- ValueDomain: more precise analysis of comparisons against an integer
literal. E.g. "x >=u 0" is always true.
git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@2565 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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for Epostincr operations.
git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@2455 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@2411 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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- C function types and Cminor signatures annotated by calling conventions.
esp. vararg / not vararg
- Cshmgen: generate correct code for function call where there are
more arguments than listed in the function prototype. This is
still undefined behavior according to the formal semantics,
but correct code is generated.
- C2C, */PrintAsm.ml: remove "printf$iif" hack.
- powerpc/, checklink/: don't generate stubs for variadic functions.
git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@2386 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@2101 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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Update ARM port.
git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@2085 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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Cstrategy: updated the big-step semantics with Eseqand and Eseqor.
git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@2062 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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Common parts are factored out in cfrontend/Ctypes.v and cfrontend/Cop.v
git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@2060 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@2059 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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and __alignof__(ty), __alignof__(expr) from GCC.
- Resurrected __builtin_memcpy_aligned, useful for files generated
by Scade KCG 6.
git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@1827 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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b and c are simple.
git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@1826 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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- native treatment of volatile accesses in CompCert C's semantics
- translation of volatile accesses to built-ins in SimplExpr
- native treatment of struct assignment and passing struct parameter by value
- only passing struct result by value remains emulated
- in cparser, remove emulations that are no longer used
- added C99's type _Bool and used it to express || and && more efficiently.
git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@1814 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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the type of the whole conditional expression.
Replaced predicates "cast", "is_true" and "is_false" by functions "sem_cast" and "bool_val".
git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@1684 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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of semantic preservation.
git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@1683 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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Clight semantics
git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@1680 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@1471 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@1470 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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- Csyntax, Csem: source C language has side-effects within expressions,
performs implicit casts, and has nondeterministic reduction semantics
for expressions
- Cstrategy: deterministic red. sem. for the above
- Clight: the previous source C language, with pure expressions.
Added: temporary variables + implicit casts.
- New pass SimplExpr to pull side-effects out of expressions
(previously done in untrusted Caml code in cparser/)
- Csharpminor: added temporary variables to match Clight.
- Cminorgen: adapted, removed cast optimization (moved to back-end)
- CastOptim: RTL-level optimization of casts
- cparser: transformations Bitfields, StructByValue and StructAssign
now work on non-simplified expressions
- Added pretty-printers for several intermediate languages,
and matching -dxxx command-line flags.
git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@1467 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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