Specifically, indexing into global arrays sometimes comes in as a big
llvm::ConstantVector, so we need to handle traversing those as well when
we do the corresponding checks in GatherScatterFlattenOpt so that we
still detect cases where we can convert them into the base pointer +
offsets form that's used in later analysis.
Allow <, <=, >, >= comparisons of pointers
Allow explicit type-casting of pointers to and from integers
Fix bug in handling expressions of the form "int + ptr" ("ptr + int"
was fine).
Fix a bug in TypeCastExpr where varying -> uniform typecasts
would be allowed (leading to a crash later)
Given IR that encoded computation like "vec(4) + ptr2int(some pointer)",
we'd report that "int2ptr(4)" was the base pointer and the ptr2int
value was the offset. This in turn could lead to incorrect code
from LLVM, since we'd end up with GEP instructions where the first
operand was int2ptr(4) and the offset was the original pointer value.
This in turn was sometimes leading to incorrect code and thence a
failure on the tests/gs-double-improve-multidim.ispc test since LLVM's
memory read/write analysis assumes that nothing after the first operand
of a GEP is actually a pointer.
Pointers can be either uniform or varying, and behave correspondingly.
e.g.: "uniform float * varying" is a varying pointer to uniform float
data in memory, and "float * uniform" is a uniform pointer to varying
data in memory. Like other types, pointers are varying by default.
Pointer-based expressions, & and *, sizeof, ->, pointer arithmetic,
and the array/pointer duality all bahave as in C. Array arguments
to functions are converted to pointers, also like C.
There is a built-in NULL for a null pointer value; conversion from
compile-time constant 0 values to NULL still needs to be implemented.
Other changes:
- Syntax for references has been updated to be C++ style; a useful
warning is now issued if the "reference" keyword is used.
- It is now illegal to pass a varying lvalue as a reference parameter
to a function; references are essentially uniform pointers.
This case had previously been handled via special case call by value
return code. That path has been removed, now that varying pointers
are available to handle this use case (and much more).
- Some stdlib routines have been updated to take pointers as
arguments where appropriate (e.g. prefetch and the atomics).
A number of others still need attention.
- All of the examples have been updated
- Many new tests
TODO: documentation
Previously, to compute the size of objects and the offsets of struct
elements within structs, we were using the trick of using getelementpointer
with a NULL base pointer and then casting the result to an int32/64.
However, since we actually know the target we're compiling for at
compile time, we can use corresponding methods from TargetData to
get these values directly.
This mostly cleans up code, but may make some of the gather/scatter
lowering to loads/stores optimizations work better in the presence
of structures.
Now, the Linker::LinkModules() call doesn't link in any functions
marked as 'internal', which is problematic, since we'd like to have
just about all of the builtins marked as internal so that they are
eliminated after they've been inlined when they are in fact used.
This change removes all of the internal qualifiers in the builtins
and adds a lSetInternalFunctions() routine to builtins.cpp that
sets this property on the functions that need it after they've
been linked in by LinkModules().
Previously, it was only in the GatherScatterFlattenOpt optimization pass that
we added the per-lane offsets when we were indexing into varying data.
(Specifically, the case of float foo[]; int index; foo[index], where foo
is an array of varying elements rather than uniform elements.) Now, this
is done in the front-end as we're first emitting code.
In addition to the basic ugliness of doing this in an optimization pass,
it was also error-prone to do it there, since we no longer have access
to all of the type information that's around in the front-end.
No functionality or performance change.
In particular, this fixes issue #81, where a global variable access was leading to
ConstantExpressions showing up in this code, which it wasn't previously expecting.
Specifically, now we can work through phi nodes in the IR to detect cases
where an index value is actually the same across lanes or is linear across
the lanes. For example, this is a loop that used to require gathers but
is now turned into vector loads:
for (int i = programIndex; i < 16; i += programCount)
sum += a[i];
Fixes issue #107.
This fixes an issue with undefined SVML symbols with code that called
transcendental functions in the stdandard library, even when the SVML
math library hadn't been selected.
Generalize the lScalarizeVector() utility routine (used in determining
when we can change gathers/scatters into vector loads/stores, respectively)
to handle vector shuffles and vector loads. This fixes issue #79, which
provided a case where a gather was being performed even though a vector
load was possible.
All of the masked store calls were inhibiting putting values into
registers, which in turn led to a lot of unnecessary stack traffic.
This approach seems to give better code in the end.
When replacing 'all on' masked store with regular store, set alignment
to be the vector element alignment, not the alignment for a whole vector.
(i.e. 4 or 8 byte alignment, not 32 or 64).
Emit calls to masked_store, not masked_store_blend, when handling
masked stores emitted by the frontend.
Fix bug in binary8to16 macro in builtins.m4
Fix bug in 16-wide version of __reduce_add_float
Remove blend function implementations for masked_store_blend for
AVX; just forward those on to the corresponding real masked store
functions.
Add optimization patterns to detect and simplify masked loads and stores
with the mask all on / all off.
Enable AVX for LLVM 3.0 builds (still generally hits bugs / unimplemented
stuff on the LLVM side, but it's getting there).
were expecting vector-width-aligned pointers where in point of fact,
there's no guarantee that they would have been in general.
Removed the aligned memory allocation routines from some of the examples;
they're no longer needed.
No perf. difference on Core2/Core i5 CPUs; older CPUs may see some
regressions.
Still need to update the documentation for this change and finish reviewing
alignment issues in Load/Store instructions generated by .cpp files.
