A macro is used to control whether struct timespec is declared, because GNO might want to declare it in other headers, and this would allow it to avoid duplicate declarations. (This will still require changes in the GNO headers. Currently, they declare struct timespec with different field names, although the layout is the same.)
In ORCA/Pascal's code generation, a case statement may use a jump table or a sequence of comparisons depending on whether it is considered sparse. This one was just a little too sparse to use a jump table, but changing it to use one makes it considerably faster. To force generation of a jump table, this commit adds several more explicit cases (even though they don't do anything).
If the return value is just a numeric constant or static address, it can simply be loaded right before the RTL instruction, avoiding any data movement.
This could actually be applied to a somewhat broader class of expressions, but for now it only applies to numeric or address constants, for which it is clearly correct.
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.
The motivation for this is that allocating and clearing symbol tables is a common operation, especially with C99+, where a construct like "if (...) { ... }" involves three levels of scope with their own symbol tables. In some tests, it could take an appreciable fraction of total execution time (sometimes ~10%).
This patch allows symbol tables that have already been allocated and cleared to be reused for a subsequent scope, as long as they are still empty. It does this by maintaining a pool of empty symbol tables and taking one from there rather than allocating a new one when possible.
We impose a somewhat arbitrary limit of MaxBlock/150000 on the number of symbol tables we keep, to avoid filling up memory with them. It would probably be better to use purgeable handles here, but that would be a little more work, and this should be good enough for now.
This mostly implements the rule in C17 6.9 p3, which requires a definition to be provided only if the function is used in an expression. Per that rule, we should also exclude most sizeof or _Alignof operands, but we don't do that yet.
Formerly, the code would allocate user IDs but never free them. The result was that one user ID was leaked for each time a CDev was opened and closed.
The new root code calls new cleanup code in ORCALib, which detects if the CDev is going away and deallocates its user ID if so.
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 would be changed to STY, but that is invalid if the A value is needed afterward. This could affect the code for certain division operations (after the optimizations in commit 4470626ade).
Here is an example that would be miscompiled:
#pragma optimize -1
#include <stdio.h>
int main(void) {
unsigned i = 55555;
unsigned a,b;
a = b = i / 10000;
printf("%u %u\n", a,b);
}
Also, remove MVN from the list of "ASafe" instructions since it really isn't, although I don't think this was affecting anything in practice.
This is necessary both to detect errors (using unary + on non-arithmetic types) and to correctly perform the integer promotions when unary + is used (which can be detected with sizeof or _Generic).
This affects calls to a varargs function that do not actually supply any arguments beyond the fixed portion of the argument list, e.g. printf("foo"). Since these calls do not supply any variable arguments, they clearly do not include any extra variable arguments beyond those used by the function, so the standards-conformance issue that requires varargs stack repair code does not apply.
It is possible that the call may include too few variable arguments, but that is illegal behavior, and it will trash the stack even when varargs stack repair code is present (although in some cases programs may "get away" with it). If stack repair code around these calls is still desired, then general stack repair code can be enabled for all function calls.
This is necessary to work correctly if the last fixed argument is of type double and #pragma extensions bit 1 is clear. It will also be necessary for C23, where va_start does not require the LastFixedParm argument. (For now, however, we stick with the pre-C23 definition of va_start where that argument needs to be supplied, even though it is now ignored.)
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).
It will now grow as needed to accommodate large segments, subject to the constraints of available memory. In practice, this mostly affects the size of initialized static arrays that can be used.
This also removes any limit apart from memory size on how large the object representation produced by a "compile to memory" can be, and cleans up error reporting regarding size limits.
This is smaller and more efficient than the previous code that called memcpy(). It also avoids a theoretical issue if the user's code included an incompatible definition of memcpy.
This allows it to use MVN-based copying code in more cases, including when moving to/from local variables on the stack. This is slightly shorter and more efficient than calling a helper function.
With the addition of designated initializers, ORCA/C now supports all the major mandatory language features added between C90 and C17, apart from those made optional by C11. There are still various small areas of nonconformance and a number of missing library functions, but at this point it is reasonable for ORCA/C to report itself as being a C17 implementation.
Long addressing was not being used to access the values, which could lead to mis-evaluation of comparisons against values in global structs, unions, or arrays, depending on the memory layout.
This could sometimes affect the c99desinit.c test, when run with large memory model and at least intermediate code peephole optimization. It could also affect this simpler test (depending on memory layout):
#pragma memorymodel 1
#pragma optimize 1
struct S {
void *p;
} s = {&s};
int main(void) {
return s.p != &s; /* should be 0 */
}
*Initialization of floating-point variables from unsigned long expressions with value > LONG_MAX would give the wrong value.
*Initialization of floating-point variables from (unsigned) long long expressions would give the wrong value.
*Initialization of _Bool variables should give 0 or 1, as per the usual rules for conversion to _Bool.
*Initialization of integer variables from floating-point expressions should be allowed, applying the usual conversions.
There is a tradeoff of code size vs. speed, since a sequence of STZ instructions is faster than a call to ~ZERO but could be quite large for a big array or struct. We now use ~ZERO for initializations of over 50 bytes to avoid excessive code bloat; the exact number chosen is somewhat arbitrary.
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.
Static initialization of arrays/structs/unions now essentially "executes" the initializer records to fill in a buffer (and keep track of relocations), then emits pcode to represent that initialized state. This supports overlapping and out-of-order initializer records, as can be produced by designated initialization.
