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This avoids a new warning of Coq 8.13.
Eventually these `Global Hint` should become `#[export] Hint`,
with a cleaner but different meaning than `Global Hint`.
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This is complementary to 28f235806
Some ABIs leave more flexibility concerning function parameters than
CompCert expects.
For instance, the AArch64/ELF ABI allow the caller of a function to
leave unspecified the "padding bits" of function parameters. As an
example, a parameter of type "unsigned char" may not have zeros in
bits 8 to 63, but may have any bits there.
When the caller is compiled by CompCert, it normalizes argument values
to the parameter types before the call, so padding bits are always
correct w.r.t. the type of the argument. This is no longer guaranteed
in interoperability scenarios, when the caller is not compiled by CompCert.
This commit adds a general mechanism to insert "re-normalization"
conversions on the parameters of a function, at function entry.
This is controlled by the platform-dependent function
Convention1.return_value_needs_normalization.
The semantic preservation proof is still conducted against the
CompCert model, where the argument values of functions are already
normalized. What the proof shows is that the extra conversions have
no effect in this case. In future work we could relax the CompCert
model, allowing functions to pass arguments that are not normalized.
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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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The "size_arguments" function and its properties can be systematically
derived from the "loc_arguments" function and its properties.
Before, the RISC-V port used this derivation, and all other ports
used hand-written "size_arguments" functions and proofs.
This commit moves the definition of "size_arguments" to the
platform-independent file backend/Conventions.v, using the systematic
derivation, and removes the platform-specific definitions.
This reduces code and proof size, and makes it easier to change the
calling conventions.
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Some ABIs leave more flexibility concerning function return values
than CompCert expects.
For example, the x86 ABI says that a function result of type "char" is
returned in register AL, leaving the top 24 bits of register EAX
unspecified, while CompCert expects EAX to contain 32 valid bits,
namely the zero- or sign-extension of the 8-bit result.
This commits adds a general mechanism to insert "re-normalization"
conversions on the results of function calls. Currently, it only
deals with results of small integer types, and inserts zero- or
sign-extensions if so instructed by a platform-dependent function,
Convention1.return_value_needs_normalization.
The conversions in question are inserted early in the front-end, so
that they can be optimized away in the back-end.
The semantic preservation proof is still conducted against the
CompCert model, where the return values of functions are already
normalized. What the proof shows is that the extra conversions have
no effect in this case. In future work we could relax the CompCert model,
allowing functions to return values that are not normalized.
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Before it was "option typ". Now it is a proper inductive type
that can also express small integer types (8/16-bit unsigned/signed integers).
One benefit is that external functions get more precise types that
control better their return values. As a consequence,
the CompCert C type preservation property now holds unconditionally,
without extra typing hypotheses on external functions.
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Replace deprecated functions and theorems from the Coq standard library (version 8.6) by their non-deprecated counterparts.
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This commit adds code generation for 64bit PowerPC architectures which execute
32bit applications.
The main difference to the normal 32bit PowerPC port is that it uses the
available 64bit instructions instead of using the runtime library functions.
However pointers are still 32bit and the 32bit calling convention is used.
In order to use this port the target architecture must be either in Server
execution mode or if in Embedded execution mode the high order 32 bits of GPRs
must be implemented in 32-bit mode. Furthermore the operating system must
preserve the high order 32 bits of GPRs.
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Adds support for the big endian arm targets by making the target
endianess flag configurable, adding support for the big endian
calling conventions, rewriting memory access patterns and adding
big endian versions of the runtime functions.
Bug 19418
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This commit changes the loc_arguments and loc_result functions that describe calling conventions so that each argument/result can be mapped either to a single location or (in the case of a 64-bit integer) to a pair of two 32-bit locations.
In the current CompCert, all arguments/results of type Tlong are systematically split in two 32-bit halves. We will need to change this in the future to support 64-bit processors. The alternative approach implemented by this commit enables the loc_arguments and loc_result functions to describe precisely which arguments need splitting. Eventually, the remainder of CompCert should not assume anything about splitting 64-bit types in two halves.
Summary of changes:
- AST: introduce the type "rpair A" of register pairs
- Conventions1, Conventions: use it when describing calling conventions
- LTL, Linear, Mach, Asm: honor the new calling conventions when observing external calls
- Events: suppress external_call', no longer useful
- All passes from Allocation to Asmgen: adapt accordingly.
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architectures
The original Stacking pass and its proof hard-wire assumptions about the processor and the register allocation, namely that integer registers are 32 bit wide and that all stack slots have natural alignment 4, which precludes having stack slots of type Tlong. Those assumptions become false if the target processor has 64-bit integer registers.
This commit makes minimal adjustments to the Stacking pass so as to lift these assumptions:
- Stack slots of type Tlong (or more generally of natural alignment 8) are supported. For slots produced by register allocation, the alignment is validated a posteriori in Lineartyping. For slots produced by the calling conventions, alignment is proved as part of the "loc_argument_acceptable" property in Conventions1.
- The code generated by Stacking to save and restore used callee-save registers no longer assumes 32-bit integer registers. Actually, it supports any combination of sizes for registers.
- To support the new save/restore code, Bounds was changed to record the set of all callee-save registers used, rather than just the max index of callee-save registers used.
On CompCert's current 32-bit target architectures, the new Stacking pass should generate pretty much the same code as the old one, modulo minor differences in the layout of the stack frame. (E.g. padding could be introduced at different places.)
The bulk of this big commit is related to the proof of the Stacking phase. The old proof strategy was painful and not obviously adaptable to the new Stacking phase, so I rewrote Stackingproof entirely, using an approach inspired by separation logic. The new library common/Separation.v defines assertions about memory states that can be composed using a separating conjunction, just like pre- and post-conditions in separation logic. Those assertions are used in Stackingproof to describe the contents of the stack frames during the execution of the generated Mach code, and relate them with the Linear location maps.
As a further simplification, the callee-save/caller-save distinction is now defined in Conventions1 by a function is_callee_save: mreg -> bool, instead of lists of registers of either kind as before. This eliminates many boring classification lemmas from Conventions1. LTL and Lineartyping were adapted accordingly.
Finally, this commit introduces a new library called Decidableplus to prove some propositions by reflection as Boolean computations. It is used to further simplify the proofs in Conventions1.
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git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@2616 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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The only platform where we have two variants is ARM, and it's easier
to share the callling convention code between the two than to maintain
both variants separately.
git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@2540 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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