The new code is smaller and (in the common case where the subtraction does not overflow) faster. It takes advantage of the fact that in overflow cases the carry flag always gets set to the opposite of the sign bit of the result.
This adds debugging code to detect null pointer dereferences, as well as pointer arithmetic on null pointers (which is also undefined behavior, and can lead to later dereferences of the resulting pointers).
Note that ORCA/Pascal can already detect null pointer dereferences as part of its more general range-checking code. This implementation for ORCA/C will report the same error as ORCA/Pascal ("Subrange exceeded"). However, it does not include any of the other forms of range checking that ORCA/Pascal does, and (unlike in ORCA/Pascal) it is controlled by a separate flag from stack overflow checking.
Varargs-only stack repair (i.e. using #pragma optimize bit 3 but not bit 6) was broken by commit 32975b720f. It removed some code that was needed to allocate the direct page location used to hold the stack pointer value in that case. This would lead to invalid code being produced, which could cause a crash when run. The fix is to revert the erroneous parts of commit 32975b720f (which do not affect its core purpose of enabling intermediate code peephole optimization to be used when stack repair code is active).
When a function has a single return statement at the end and meets certain other constraints, we now generate a different intermediate code instruction to evaluate the return value as part of the return operation, rather than assigning it to (effectively) a variable and then reading that value again to return it.
This approach could actually be used for all returns in C code, but for now we only use it for a single return at the end. Directly applying it in other cases could increase the code size by duplicating the function epilogue code.
This would previously happen if a segment directive with "dynamic" appeared before the first function in the program. That would cause the resulting program not to work, because the root segment needs to be a static segment at the start of the program, but if it is dynamic it would come after a jump table and a static segment of library code.
The root segments are also configured to refer to main or the NDA/CDA entry points using LEXPR records, so that they can be in dynamic segments (not that they necessarily should be). That change is intentionally not done for CDEV/XCMD/NBA, because they use code resources, which do not support dynamic segments, so it is better to force a linker error in these cases.
I think the reason this was originally disallowed is that the old code sequence for stack repair code (in ORCA/C 2.1.0) ended with TYA. If this was followed by STA dp or STA abs, the native code peephole optimizer (prior to commit 7364e2d2d3) would have turned the combination into a STY instruction. That is invalid if the value in A is needed. This could come up, e.g., when assigning the return value from a function to two different variables.
This is no longer an issue, because the current code sequence for stack repair code no longer ends in TYA and is not susceptible to the same kind of invalid optimization. So it is no longer necessary to disable the native code peephole optimizer when using stack repair code (either for all calls or just varargs calls).
This provides a more straightforward way to place the compiler in a "strict conformance" mode. This could essentially be achieved by setting several pragma options, but having a single setting is simpler. "Compatibility modes" for older standards can also be selected, although these actually continue to enable most C17 features (since they are unlikely to cause compatibility problems for older code).
This avoids needing to generate many intermediate code records representing the data at most 8 bytes at a time, which should reduce memory use and probably improve performance for large initialized arrays or structs.
The branch range calculation treated dcl directives as taking 2 bytes rather than 4, which could result in out-of-range branches. These could result in linker errors (for forward branches) or silently generating wrong code (for backward branches).
This patch now treats dcb, dcw, and dcl as separate directives in the native-code layer, so the appropriate length can be calculated for each.
Here is an example of code affected by this:
int main(int argc, char **argv) {
top:
if (!argc) { /* this caused a linker error */
asm {
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
dcl 0
}
goto top; /* this generated bad code with no error */
}
}
Previously, the assembly-level optimizations applied to code in asm statements. In many cases, this was fine (and could even do useful optimizations), but occasionally the optimizations could be invalid. This was especially the case if the assembly involved tricky things like self-modifying code.
To avoid these problems, this patch makes the assembly optimizers ignore code from asm statements, so it is always emitted as-is, without any changes.
This fixes#34.
This differs from the usual ORCA/C behavior of treating all floating-point parameters as extended. With the option enabled, they will still be passed in the extended format, but will be converted to their declared type at the start of the function. This is needed for strict standards conformance, because you should be able to take the address of a parameter and get a usable pointer to its declared type. The difference in types can also affect the behavior of _Generic expressions.
The implementation of this is based on ORCA/Pascal, which already did the same thing (unconditionally) with real/double/comp parameters.
They now use a jmp (addr,X) instruction, rather than a more complicated code sequence using rts. This is an improvement that was suggested in an old Genie message from Todd Whitesel.
This converts comparisons like x > N (with constant N) to instead be evaluated as x >= N+1, since >= comparisons generate better code. This is possible as long as N is not the maximum value in the type, but in that case the comparison is always false. There are also a few other tweaks to the generated code in some cases.
The new value of maxLocalLabel is aligned with the C99+ requirement to support "511 identifiers with block scope declared in one block".
The value of maxLabel is now the maximum it can be while keeping the size of the labelTab array under 32 KiB. (I'm not entirely sure the address calculations in the code generated by ORCA/Pascal would work correctly beyond that.)
This optimizes most multiplications by a power of 2 or the sum of two powers of 2, converting them to equivalent operations using shifts which should be faster than the general-purpose multiplication routine.
There were several existing optimizations that could change behavior in ways that violated the IEEE standard with regard to infinities, NaNs, or signed zeros. They are now gated behind a new #pragma optimize flag. This change allows intermediate code peephole optimization and common subexpression elimination to be used while maintaining IEEE conformance, but also keeps the rule-breaking optimizations available if desired.
See section F.9.2 of recent C standards for a discussion of how these optimizations violate IEEE rules.
The C standards generally allow floating-point operations to be done with extra range and precision, but they require that explicit casts convert to the actual type specified. ORCA/C was not previously doing that.
This patch relies on some new library routines (currently in ORCALib) to do this precision reduction.
This fixes#64.
This means that floating-point constants can now have the range and precision of the extended type (aka long double), and floating-point constant expressions evaluated within the compiler also have that same range and precision (matching expressions evaluated at run time). This new behavior is intended to match the behavior specified in the C99 and later standards for FLT_EVAL_METHOD 2.
This fixes the previous problem where long double constants and constant expressions of type long double were not represented and evaluated with the full range and precision that they should be. It also gives extra range and precision to constants and constant expressions of type double or float. This may have pluses and minuses, but at any rate it is consistent with the existing behavior for expressions evaluated at run time, and with one of the possible models of floating point evaluation specified in the C standards.
These instructions can be generated for indirect accesses to quad values, and the optimization can sometimes make those code sequences more efficient (e.g. avoiding unnecessary reloads of Y).
This works when both operands are simple loads, such that they can be broken up into operations on their subwords in a standard format.
Currently, this is implemented for bitwise binary ops, but it can also be expanded to arithmetic, etc.
This has no functional effect, since it is all comments. It does mean that printed listings of CGI.pas would not contain those comments, but it is easy enough to restore if someone wants such listings.
This change should make compilation slightly faster, and it also avoids issues with filetypes when using certain tools (since they cannot infer the filetype of CGI.Comments from its extension).
Currently, the actual values they can have are still constrained to the 32-bit range. Also, there are some bits of functionality (e.g. for initializers) that are not implemented yet.
If there are no varargs calls (and nothing else that saves stack positions), then space doesn't need to be allocated for the saved stack position. This can also lead to more efficient prolog/epilog code for small functions.
These are enabled when bit 15 is set in the #pragma debug directive.
Support is still needed to ensure these work properly with pre-compiled headers.
This patch is from Kelvin Sherlock.
This is necessary to compile some very large functions, such as the main interpreter loop in Git.
This consumes about 8K of extra memory for the additional label records.
The issue was that 16-bit absolute addressing (in the data bank) was being used to access the data to compare, but with the large memory model the static arrays or structs are not necessarily in the same bank, so absolute long addressing should be used.
This was sometimes causing failures in the C4.6.4.1.CC and C4.6.6.1.CC conformance tests in the ORCA/C test suite.
The following program often demonstrates the problem (depending on memory layout and contents):
#pragma memorymodel 1
#pragma optimize 1
#include <stdio.h>
int i;
char ch1[32000];
long L1[1];
int main (void)
{
if (L1 [0] != 0)
printf("%li\n", L1[0]); /* shouldn't print */
/* buggy behavior can happen if the bank bytes of these pointers differ */
printf("%p %p\n", &L1[0], &i);
}
The latter would require more changes to the code generator to understand it, whereas this approach doesn't require any changes. This is arguably less clean, but it matches other places where a byte value is subsequently operated on as a word without an explicit conversion, and the assembly instruction generated is the same.
This fixes the compca06.c test case.
Note that this generates inefficient code in the case of loading a signed byte value and then immediately casting it to unsigned (it first sign-extends the value, then masks off the high bits). This should be optimized, but at least the generated code is correct now.
