The decl.* code now no longer interacts with Symbols, but just returns
names, types, initializer expressions, etc., as needed. This makes the
code a bit more understandable.
Fixes issues #171 and #130.
Both ReturnStmt and DeclStmt now check the values being associated
with references to make sure that they are legal (e.g. it's illegal
to assign a varying lvalue, or a compile-time constant to a reference
type). Previously we didn't catch this and would end up hitting
assertions in LLVM when code did this stuff.
Mostly fixes issue #225 (except for adding a FAQ about what this
error message means.)
Because they reestablish an 'all on' mask inside their body, it doesn't
make sense to include their cost when evaluating whether it's worth
re-establishing an 'all on' mask dynamically. (This does mean that
EstimateCost()'s return value isn't the most obvious thing, but currently
in all the cases where we need it, this is the more appropriate value to
return.)
We now have separate Expr implementations for dereferencing pointers
and automatically dereferencing references. This is in particular
necessary so that we can detect attempts to dereference references
with the '*' operator in programs and issue an error in that case.
Fixes issue #192.
safe: indicates that the function can safely be called with an "all off"
execution mask.
costN: (N an integer) overrides the cost estimate for the function with
the given value.
We now follow C's approach of evaluating these: we don't evaluate
the second expression in the operator if the value of the first one
determines the overall result. Thus, these can now be used
idiomatically like (index < limit && array[index] > 0) and such.
For varying expressions, the mask is set appropriately when evaluating
the second expression.
(For expressions that can be determined to be both simple and safe to
evaluate with the mask all off, we still evaluate both sides and compute
the logical op result directly, which saves a number of branches and tests.
However, the effect of this should never be visible to the programmer.)
Issue #4.
Switches with both uniform and varying "switch" expressions are
supported. Switch statements with varying expressions and very
large numbers of labels may not perform well; some issues to be
filed shortly will track opportunities for improving these.
ispc now supports goto, but only under uniform control flow--i.e.
it must be possible for the compiler to statically determine that
all program instances will follow the goto. An error is issued at
compile time if a goto is used when this is not the case.
Specifically, stmts and exprs are no longer responsible for first recursively
optimizing their children before doing their own optimization (this turned
out to be error-prone, with children sometimes being forgotten.) They now
are just responsible for their own optimization, when appropriate.
In general, it should just return the original node pointer, but for type checking
and optimization passes, it can return a new value for the node (that will be
assigned where the old one was in the tree.)
Along the way, fixed some bugs in WalkAST() where the postorder callback wouldn't
end up being called for a few expr types (sizeof, dereference, address of,
reference).
For starters, use it for the check to see if code is safe to run with the
mask all off.
This also fixes a bug where we would sometimes incorrectly say that
a whole block of code was unsafe to run with an all off mask because we came
to a NULL AST node during traversal.
Substantial improvements and generalizations to the parsing and
declaration handling code to properly parse declarations involving
pointers. (No change to user-visible functionality, but this
lays groundwork for supporting a more general pointer model.)
The stuff in decl.h/decl.cpp is messy, largely due to its close mapping
to C-style variable declarations. This checkin has updated code throughout
all of the declaration statement, variable, and function code that operates
on symbols and types directly. Thus, Decl* related stuff is now localized
to decl.h/decl.cpp and the parser.
Issue #13.
Added AST and Function classes.
Now, we parse the whole file and build up the AST for all of the
functions in the Module before we emit IR for the functions (vs. before,
when we generated IR along the way as we parsed the source file.)
