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With FP arithmetic, the negation of "x < y" is not "x >= y". For this reason, the back-end intermediate languages of CompCert used to have both "Ccompf c" and "Cnotcompf c" comparison operators, where "c" is of type Integers.comparison and "Cnotcompf c" denotes the negation of FP comparison c.
There are some problems with this approach:
- Beyond Cnotcompf we also need Cnotcompfs (for single precision FP) and, in case of ARM, special forms for not-comparison against 0.0. This duplication of comparison constructors inevitably causes some code and proof duplication.
- Cnotcompf Ceq is really Ccompf Cne, and likewise Cnotcompf Cne is really Ccompf Ceq, hence the representation of FP comparisons is not canonical, adding to the code and proof duplication mentioned above.
- Cnotcompf is introduced in CminorSel, but in Cminor we don't have it, making it impossible to express some transformations over comparisons at the machine-independent Cminor level.
This commit develops an alternate approach, whereas FP comparisons have their own type, defined as Floats.fp_comparison, and which includes constructors for "not <", "not <=", "not >" and "not >=". Hence this type is closed under boolean negation, so to speak, and there is no longer a need for "Cnotcompf", given that "Ccompf" takes a fp_comparison and can therefore express all FP comparisons of interest.
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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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The PowerPC port remains 32-bit only, no support is added for PPC 64.
This shows how much work is needed to update an existing port a minima.
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Also: implement __builtin_isel on non-EREF platforms with a branch-free instruction sequence.
Also: extend ./configure so that it recognizes "ppc64-" and "e5500-" platforms in addition to "ppc-".
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operations with undefined behaviors.
Consider (x ^ 1) ^ 1 where x is a intptr_t containing a pointer value. "x ^ 1" evaluates to Vundef in the CompCert semantics, hence the value analysis, in strict mode, gives abstract result Ifptr Pbot (= any number but not a pointer). In relaxed mode, we now give abstract result Ifptr (poffset p) where p is the abstraction of the pointer, thus keeping track of the actual leak of the pointer value.
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- Support single-precision floats as first-class values
- Introduce chunks Many32, Many64 and types Tany32, Tany64 to
support saving and restoring registers without knowing
the exact types (int/single/float) of their contents, just
their sizes.
- Memory model: generalize the opaque encoding of pointers to
apply to any value, not just pointers, if chunks Many32/Many64
are selected.
- More properties of FP arithmetic proved.
git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@2537 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@2503 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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Refactored compilation flags that affect the Coq part (module Compopts).
Added support for C99 for loops with declarations.
git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@2410 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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NeedOp, Deadcode: must have distinct needs per argument of an operator.
This change remains to be propagated to IA32 and PPC.
git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@2399 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@2381 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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