The meaning of getTypeSize was not clear - clarifying it is important
now that we have x86 long double and arbitrary precision integers.
The issue with long double is that it requires 80 bits, and this is
not a multiple of its alignment. This gives a primitive type for
which getTypeSize differed from getABITypeSize. For arbitrary precision
integers it is even worse: there is the minimum number of bits needed to
hold the type (eg: 36 for an i36), the maximum number of bits that will
be overwriten when storing the type (40 bits for i36) and the ABI size
(i.e. the storage size rounded up to a multiple of the alignment; 64 bits
for i36).
This patch removes getTypeSize (not really - it is still there but
deprecated to allow for a gradual transition). Instead there is:
(1) getTypeSizeInBits - a number of bits that suffices to hold all
values of the type. For a primitive type, this is the minimum number
of bits. For an i36 this is 36 bits. For x86 long double it is 80.
This corresponds to gcc's TYPE_PRECISION.
(2) getTypeStoreSizeInBits - the maximum number of bits that is
written when storing the type (or read when reading it). For an
i36 this is 40 bits, for an x86 long double it is 80 bits. This
is the size alias analysis is interested in (getTypeStoreSize
returns the number of bytes). There doesn't seem to be anything
corresponding to this in gcc.
(3) getABITypeSizeInBits - this is getTypeStoreSizeInBits rounded
up to a multiple of the alignment. For an i36 this is 64, for an
x86 long double this is 96 or 128 depending on the OS. This is the
spacing between consecutive elements when you form an array out of
this type (getABITypeSize returns the number of bytes). This is
TYPE_SIZE in gcc.
Since successive elements in a SequentialType (arrays, pointers
and vectors) need to be aligned, the spacing between them will be
given by getABITypeSize. This means that the size of an array
is the length times the getABITypeSize. It also means that GEP
computations need to use getABITypeSize when computing offsets.
Furthermore, if an alloca allocates several elements at once then
these too need to be aligned, so the size of the alloca has to be
the number of elements multiplied by getABITypeSize. Logically
speaking this doesn't have to be the case when allocating just
one element, but it is simpler to also use getABITypeSize in this
case. So alloca's and mallocs should use getABITypeSize. Finally,
since gcc's only notion of size is that given by getABITypeSize, if
you want to output assembler etc the same as gcc then getABITypeSize
is the size you want.
Since a store will overwrite no more than getTypeStoreSize bytes,
and a read will read no more than that many bytes, this is the
notion of size appropriate for alias analysis calculations.
In this patch I have corrected all type size uses except some of
those in ScalarReplAggregates, lib/Codegen, lib/Target (the hard
cases). I will get around to auditing these too at some point,
but I could do with some help.
Finally, I made one change which I think wise but others might
consider pointless and suboptimal: in an unpacked struct the
amount of space allocated for a field is now given by the ABI
size rather than getTypeStoreSize. I did this because every
other place that reserves memory for a type (eg: alloca) now
uses getABITypeSize, and I didn't want to make an exception
for unpacked structs, i.e. I did it to make things more uniform.
This only effects structs containing long doubles and arbitrary
precision integers. If someone wants to pack these types more
tightly they can always use a packed struct.
llvm-svn: 43620
1. Fix the macros in IncludeFile.h to put everything in the llvm namespace
2. Replace the previous explicit mechanism in all the .h and .cpp files
with the macros in IncludeFile.h
This gets us a consistent mechanism throughout LLVM for ensuring linkage.
Next step is to make sure its used in enough places.
llvm-svn: 28715
Break the "IncludeFile" mechanism into its own header file and adjust other
files accordingly. Use this facility for the IntrinsicInst problem which
was the subject of PR800.
More to follow on this.
llvm-svn: 28709
IncludeFile hack to ensure linkage of analysis passes. This works around
some -pedantic warnings about assigning an object to a function.
llvm-svn: 28621
* Takes into account the size of the memory reference to determine aliasing.
* Expose mod/ref information in a more consistent way
* BasicAA can now disambiguate A[i][1] and A[j][2] for conservative request
sizes
llvm-svn: 5633
- A[c1] cannot alias A[c2] where constants c1 != c2
- A[i] cannot alias B[j] if A & B are provably different arrays
This should help out array based codes. For example, from bzip2 from spec,
3 additional loads can be GCSE'd, and _21_ additional loads can be LICMd due
to this change.
In a test example from the Spec GAP benchmark (vecffe.c), this change allows
_52_ additional loads to be GCSE'd and _224_ additional LICM'd loads.
Not bad for such a simple change. Other testcases show no change at all
because they just don't use arrays. Not too suprising there.
llvm-svn: 3616
Duncan Sands