Commit Graph

274 Commits

Author SHA1 Message Date
Nick Lewycky
9e26c1cc0c Fix a crasher trying to fold each element in a comparison between two vectors
if one of the vectors didn't have elements (such as undef). Fixes PR 6096.

Fix an issue in the constant folder where fcmp (<2 x %ty>, <2 x %ty>) would
have <2 x i1> type if constant folding was successful and i1 type if it wasn't.
This exposed a related issue in the bitcode reader.

llvm-svn: 94069
2010-01-21 07:03:21 +00:00
Victor Hernandez
108d3acb43 Parse function-local metadata inside function blocks
llvm-svn: 93337
2010-01-13 19:34:08 +00:00
Devang Patel
8992323bb9 s/NextValueNo/NextMDValueNo while processing metadata.
llvm-svn: 93165
2010-01-11 18:52:33 +00:00
Victor Hernandez
b8fd152d94 Compute isFunctionLocal in MDNode ctor or via argument in new function getWhenValsUnresolved().
Document PFS argument to ParseValID() and ConvertGlobalOrMetadataValIDToValue().

llvm-svn: 93108
2010-01-10 07:14:18 +00:00
Chris Lattner
003143c582 clean up this code, add a fixme.
llvm-svn: 93042
2010-01-09 02:02:37 +00:00
Devang Patel
330cde488e NamedMDNode element is either null or MDNode. Otherwise this is a malformed NamedMDNode record.
llvm-svn: 93037
2010-01-09 01:02:22 +00:00
Devang Patel
6edcd3994c Allow null to be an element of NamedMDNode. e.g. !llvm.stuff = !{!0, !1, null}
llvm-svn: 92783
2010-01-05 21:47:32 +00:00
Devang Patel
e307348325 NamedMDNode is a collection MDNodes.
llvm-svn: 92761
2010-01-05 20:41:31 +00:00
Benjamin Kramer
ccce8bae14 Avoid going through the LLVMContext for type equality where it's safe to dereference the type pointer.
llvm-svn: 92726
2010-01-05 13:12:22 +00:00
Chris Lattner
a0566979b7 Final step in the metadata API restructuring: move the
getMDKindID/getMDKindNames methods to LLVMContext (and add
convenience methods to Module), eliminating MetadataContext.
Move the state that it maintains out to LLVMContext.

llvm-svn: 92259
2009-12-29 09:01:33 +00:00
Chris Lattner
2f2aa2b067 This is a major cleanup of the instruction metadata interfaces that
I asked Devang to do back on Sep 27.  Instead of going through the
MetadataContext class with methods like getMD() and getMDs(), just
ask the instruction directly for its metadata with getMetadata()
and getAllMetadata().

This includes a variety of other fixes and improvements: previously
all Value*'s were bloated because the HasMetadata bit was thrown into
value, adding a 9th bit to a byte.  Now this is properly sunk down to
the Instruction class (the only place where it makes sense) and it
will be folded away somewhere soon.

This also fixes some confusion in getMDs and its clients about 
whether the returned list is indexed by the MDID or densely packed.
This is now returned sorted and densely packed and the comments make
this clear.

This introduces a number of fixme's which I'll follow up on.

llvm-svn: 92235
2009-12-28 23:41:32 +00:00
Chris Lattner
7093946ab1 rename getMDKind -> getMDKindID, make it autoinsert if an MD Kind
doesn't exist already, eliminate registerMDKind.  Tidy up a bunch
of random stuff.

llvm-svn: 92225
2009-12-28 20:45:51 +00:00
Victor Hernandez
f3db915294 Re-commit r86077 now that r86290 fixes the 179.art and 175.vpr ARM regressions.
Here is the original commit message:

This commit updates malloc optimizations to operate on malloc calls that have constant int size arguments.

Update CreateMalloc so that its callers specify the size to allocate:
MallocInst-autoupgrade users use non-TargetData-computed allocation sizes.
Optimization uses use TargetData to compute the allocation size.

Now that malloc calls can have constant sizes, update isArrayMallocHelper() to use TargetData to determine the size of the malloced type and the size of malloced arrays.
Extend getMallocType() to support malloc calls that have non-bitcast uses.

Update OptimizeGlobalAddressOfMalloc() to optimize malloc calls that have non-bitcast uses.  The bitcast use of a malloc call has to be treated specially here because the uses of the bitcast need to be replaced and the bitcast needs to be erased (just like the malloc call) for OptimizeGlobalAddressOfMalloc() to work correctly.

Update PerformHeapAllocSRoA() to optimize malloc calls that have non-bitcast uses.  The bitcast use of the malloc is not handled specially here because ReplaceUsesOfMallocWithGlobal replaces through the bitcast use.

Update OptimizeOnceStoredGlobal() to not care about the malloc calls' bitcast use.

Update all globalopt malloc tests to not rely on autoupgraded-MallocInsts, but instead use explicit malloc calls with correct allocation sizes.

llvm-svn: 86311
2009-11-07 00:16:28 +00:00
Victor Hernandez
b9f5899779 Revert r86077 because it caused crashes in 179.art and 175.vpr on ARM
llvm-svn: 86213
2009-11-06 01:33:24 +00:00
Victor Hernandez
492ed30a32 Update CreateMalloc so that its callers specify the size to allocate:
MallocInst-autoupgrade users use non-TargetData-computed allocation sizes.
Optimization uses use TargetData to compute the allocation size.

Now that malloc calls can have constant sizes, update isArrayMallocHelper() to use TargetData to determine the size of the malloced type and the size of malloced arrays.
Extend getMallocType() to support malloc calls that have non-bitcast uses.

Update OptimizeGlobalAddressOfMalloc() to optimize malloc calls that have non-bitcast uses.  The bitcast use of a malloc call has to be treated specially here because the uses of the bitcast need to be replaced and the bitcast needs to be erased (just like the malloc call) for OptimizeGlobalAddressOfMalloc() to work correctly.

Update PerformHeapAllocSRoA() to optimize malloc calls that have non-bitcast uses.  The bitcast use of the malloc is not handled specially here because ReplaceUsesOfMallocWithGlobal replaces through the bitcast use.

Update OptimizeOnceStoredGlobal() to not care about the malloc calls' bitcast use.

Update all globalopt malloc tests to not rely on autoupgraded-MallocInsts, but instead use explicit malloc calls with correct allocation sizes.

llvm-svn: 86077
2009-11-05 00:03:03 +00:00
Chris Lattner
aa99c94e2a Revert 85678/85680. The decision is to stay with the current form of
indirectbr, thus we don't need "blockaddr(@func, null)".  Eliminate it
for simplicity.

llvm-svn: 85699
2009-11-01 01:27:45 +00:00
Chris Lattner
b2c0e243c5 Make blockaddress(@func, null) be valid, and make 'deleting a basic
block with a blockaddress still referring to it' replace the invalid 
blockaddress with a new blockaddress(@func, null) instead of a 
inttoptr(1).

This changes the bitcode encoding format, and still needs codegen 
support (this should produce a non-zero value, referring to the entry
block of the function would also be quite reasonable).

llvm-svn: 85678
2009-10-31 20:08:37 +00:00
Chris Lattner
5956dc87d3 add bitcode reader support for blockaddress. We can now fully
round trip blockaddress through .ll and .bc files, so add a testcase.

There are still a bunch of places in the optimizer and other places
that need to be updated to work with these constructs, but at least
the basics are in now.

llvm-svn: 85377
2009-10-28 05:53:48 +00:00
Chris Lattner
d04cb6d0fa rename indbr -> indirectbr to appease the residents of #llvm.
llvm-svn: 85351
2009-10-28 00:19:10 +00:00
Chris Lattner
3ed871fe62 add enough support for indirect branch for the feature test to pass
(assembler,asmprinter, bc reader+writer) and document it.  Codegen
currently aborts on it.

llvm-svn: 85274
2009-10-27 19:13:16 +00:00
Daniel Dunbar
3d913cda5f Suppress -Asserts warning.
llvm-svn: 85078
2009-10-25 23:11:06 +00:00
Victor Hernandez
e297149e26 Auto-upgrade free instructions to calls to the builtin free function.
Update all analysis passes and transforms to treat free calls just like FreeInst.
Remove RaiseAllocations and all its tests since FreeInst no longer needs to be raised.

llvm-svn: 84987
2009-10-24 04:23:03 +00:00
Devang Patel
1155fdf6dc Hide MetadataContext implementation details.
llvm-svn: 84886
2009-10-22 19:36:54 +00:00
Dale Johannesen
1cfb958b00 Rename msasm to alignstack per review.
llvm-svn: 84795
2009-10-21 23:28:00 +00:00
Victor Hernandez
be9e179104 Make changes to rev 84292 as requested by Chris Lattner.
Most changes are cleanup, but there is 1 correctness fix:
I fixed InstCombine so that the icmp is removed only if the malloc call is removed (which requires explicit removal because the Worklist won't DCE any calls since they can have side-effects).

llvm-svn: 84772
2009-10-21 19:11:40 +00:00
Victor Hernandez
c7d6a8327c Autoupgrade malloc insts to malloc calls.
Update testcases that rely on malloc insts being present.

Also prematurely remove MallocInst handling from IndMemRemoval and RaiseAllocations to help pass tests in this incremental step.

llvm-svn: 84292
2009-10-17 00:00:19 +00:00
Dale Johannesen
fd04c74bc0 Add an "msasm" flag to inline asm as suggested in PR 5125.
A little ugliness is accepted to keep the binary file format
compatible.  No functional change yet.

llvm-svn: 84020
2009-10-13 20:46:56 +00:00
Devang Patel
0b26c9e0b3 Remove unnecessary assert.
llvm-svn: 84004
2009-10-13 18:51:03 +00:00
Chris Lattner
fdd8790718 strength reduce a ton of type equality tests to check the typeid (Through
the new predicates I added) instead of going through a context and doing a
pointer comparison.  Besides being cheaper, this allows a smart compiler
to turn the if sequence into a switch.

llvm-svn: 83297
2009-10-05 05:54:46 +00:00
Devang Patel
5bf7a49fd7 Only one custom meadata of each kind can be attached with an instruction.
llvm-svn: 83105
2009-09-29 20:30:57 +00:00
Devang Patel
2d85eef974 s/class Metadata/class MetadataContext/g
llvm-svn: 83019
2009-09-28 21:41:20 +00:00
Devang Patel
b1a4477f1f Do not use global typedef for MDKindID.
llvm-svn: 83016
2009-09-28 21:14:55 +00:00
Victor Hernandez
e6ff7662b6 Revert 82694 "Auto-upgrade malloc instructions to malloc calls." because it causes regressions in the nightly tests.
llvm-svn: 82784
2009-09-25 18:11:52 +00:00
Victor Hernandez
46cd467310 Auto-upgrade malloc instructions to malloc calls.
Reviewed by Devang Patel.

llvm-svn: 82694
2009-09-24 17:47:49 +00:00
Daniel Dunbar
7d6781b0fe Tabs -> spaces, and remove trailing whitespace.
llvm-svn: 82355
2009-09-20 02:20:51 +00:00
Devang Patel
af206b8c88 Write and read metadata attachments.
llvm-svn: 82259
2009-09-18 19:26:43 +00:00
Dan Gohman
1b84908f92 Reappy r80998, now that the GlobalOpt bug that it exposed on MiniSAT is fixed.
llvm-svn: 81172
2009-09-07 23:54:19 +00:00
Duncan Sands
0f5bbb585c Public and private corrections, warned about by icc (#304).
Patch by Erick Tryzelaar.

llvm-svn: 81107
2009-09-06 08:55:57 +00:00
Daniel Dunbar
10ea8bb8e0 Revert "Include optional subclass flags, such as inbounds, nsw, etc., ...", this
breaks MiniSAT on x86_64.

llvm-svn: 81098
2009-09-06 00:11:24 +00:00
Dan Gohman
0c2477c26b Include optional subclass flags, such as inbounds, nsw, etc., in the
Constant uniquing tables. This allows distinct ConstantExpr objects
with the same operation and different flags.

Even though a ConstantExpr "a + b" is either always overflowing or
never overflowing (due to being a ConstantExpr), it's still necessary
to be able to represent it both with and without overflow flags at
the same time within the IR, because the safety of the flag may
depend on the context of the use. If the constant really does overflow,
it wouldn't ever be safe to use with the flag set, however the use
may be in code that is never actually executed.

This also makes it possible to merge all the flags tests into a single test.

llvm-svn: 80998
2009-09-04 12:08:11 +00:00
Devang Patel
116b4a0cb3 Add new value for given index in MDValuePtrs.
llvm-svn: 80867
2009-09-03 01:38:02 +00:00
Sandeep Patel
68c5f477fa Retype from unsigned to CallingConv::ID accordingly. Approved by Bob Wilson.
llvm-svn: 80773
2009-09-02 08:44:58 +00:00
Devang Patel
80ae34974b Reapply 79977.
Use MDNodes to encode debug info in llvm IR.

llvm-svn: 80406
2009-08-28 23:24:31 +00:00
Devang Patel
f08e35d9dc Revert 79977. It causes llvm-gcc bootstrap failures on some platforms.
llvm-svn: 80073
2009-08-26 05:01:18 +00:00
Dan Gohman
ad1f0a1101 Eliminate the unused Context argument on one of the ICmpInst and FCmpInst
constructors.

llvm-svn: 80049
2009-08-25 23:17:54 +00:00
Devang Patel
02aac922b4 Update DebugInfo interface to use metadata, instead of special named llvm.dbg.... global variables, to encode debugging information in llvm IR. This is mostly a mechanical change that tests metadata support very well.
This change speeds up llvm-gcc by more then 6% at "-O0 -g" (measured by compiling InstructionCombining.cpp!)

llvm-svn: 79977
2009-08-25 05:24:07 +00:00
Dan Gohman
16f5415f5b Rename hasNoUnsignedOverflow and hasNoSignedOverflow to hasNoUnsignedWrap
and hasNoSignedWrap, for consistency with the nuw and nsw properties.

llvm-svn: 79539
2009-08-20 17:11:38 +00:00
Daniel Dunbar
8b0b11582d Switch to SmallString::str from SmallString::c_str, and remove
SmallString::c_str.

llvm-svn: 79456
2009-08-19 20:07:03 +00:00
Owen Anderson
a42ac6953b Actually privatize a IntegerTypes, and fix a few bugs exposed by this.
llvm-svn: 78955
2009-08-13 23:27:32 +00:00
Owen Anderson
55f1c09e31 Push LLVMContexts through the IntegerType APIs.
llvm-svn: 78948
2009-08-13 21:58:54 +00:00
Owen Anderson
03cb69fbd1 Privatize the StructType table, which unfortunately involves routing contexts through a number of APIs.
llvm-svn: 78258
2009-08-05 23:16:16 +00:00
Devang Patel
05eb617da5 Use separate ValueList for metadata.
This fixes PR4666.

llvm-svn: 78056
2009-08-04 06:00:18 +00:00
Owen Anderson
0087fe6e5c Move the metadata constructors back to 2.5 syntax.
llvm-svn: 77733
2009-07-31 21:35:40 +00:00
Owen Anderson
5a1acd9912 Move a few more APIs back to 2.5 forms. The only remaining ones left to change back are
metadata related, which I'm waiting on to avoid conflicting with Devang.

llvm-svn: 77721
2009-07-31 20:28:14 +00:00
Owen Anderson
b292b8ce70 Move more code back to 2.5 APIs.
llvm-svn: 77635
2009-07-30 23:03:37 +00:00
Devang Patel
27c87fff7f Read and write NamedMDNode.
llvm-svn: 77517
2009-07-29 22:34:41 +00:00
Owen Anderson
4056ca9568 Move types back to the 2.5 API.
llvm-svn: 77516
2009-07-29 22:17:13 +00:00
Owen Anderson
487375e9a2 Move ConstantExpr to 2.5 API.
llvm-svn: 77494
2009-07-29 18:55:55 +00:00
Devang Patel
a4f43fb5dd Rename MDNode.h header. It defines MDnode and other metadata classes.
New name is Metadata.h.

llvm-svn: 77370
2009-07-28 21:49:47 +00:00
Owen Anderson
4aa3295a65 Return ConstantVector to 2.5 API.
llvm-svn: 77366
2009-07-28 21:19:26 +00:00
Owen Anderson
c2c7932c64 Change ConstantArray to 2.5 API.
llvm-svn: 77347
2009-07-28 18:32:17 +00:00
Owen Anderson
45308b578b Move ConstantStruct back to 2.5 API.
llvm-svn: 77266
2009-07-27 22:29:26 +00:00
Dan Gohman
1639c3905e Add a new keyword 'inbounds' for use with getelementptr. See the
LangRef.html changes for details.

llvm-svn: 77259
2009-07-27 21:53:46 +00:00
Owen Anderson
69c464dec4 Move ConstantFP construction back to the 2.5-ish API.
llvm-svn: 77247
2009-07-27 20:59:43 +00:00
Daniel Dunbar
d786b51ea4 Remove Value::setName(const char*, unsigned).
llvm-svn: 77100
2009-07-26 00:34:27 +00:00
Daniel Dunbar
d43b86d4a4 Finish migrating VMCore to StringRef/Twine based APIs.
llvm-svn: 77051
2009-07-25 06:02:13 +00:00
Eric Christopher
c974225976 Move ExtractElementInst to ::Create instead of new. Update all uses.
llvm-svn: 77044
2009-07-25 02:28:41 +00:00
Owen Anderson
edb4a70325 Revert the ConstantInt constructors back to their 2.5 forms where possible, thanks to contexts-on-types. More to come.
llvm-svn: 77011
2009-07-24 23:12:02 +00:00
Devang Patel
6292003492 MDString
- Rename member function size(). New name is length().
- Store string beginning and length. Earlier it used to store string end.

llvm-svn: 76841
2009-07-23 02:00:51 +00:00
Devang Patel
e059ba6ed2 Derive MDNode from MetadataBase instead of Constant. Emit MDNodes into METADATA_BLOCK in bitcode file.
llvm-svn: 76834
2009-07-23 01:07:34 +00:00
Devang Patel
7428d8acec Introduce MetadataBase, a base class for MDString and MDNode.
Derive MDString directly from MetadataBase. 
Introduce new bitcode block to hold metadata.

llvm-svn: 76759
2009-07-22 17:43:22 +00:00
Dan Gohman
0ebd69614c Assembly and Bitcode support for unsigned/signed overflow flags and
exact sdiv flags.

llvm-svn: 76475
2009-07-20 21:19:07 +00:00
Bill Wendling
a3c6f6bffa Add plumbing for the `linker_private' linkage type. This type is meant for
"private" symbols which the assember shouldn't strip, but which the linker may
remove after evaluation. This is mostly useful for Objective-C metadata.

This is plumbing, so we don't have a use of it yet. More to come, etc.

llvm-svn: 76385
2009-07-20 01:03:30 +00:00
Owen Anderson
4fdeba9706 Revert yesterday's change by removing the LLVMContext parameter to AllocaInst and MallocInst.
llvm-svn: 75863
2009-07-15 23:53:25 +00:00
Owen Anderson
b6b2530000 Move EVER MORE stuff over to LLVMContext.
llvm-svn: 75703
2009-07-14 23:09:55 +00:00
Owen Anderson
1e5f00e7a7 This started as a small change, I swear. Unfortunately, lots of things call the [I|F]CmpInst constructors. Who knew!?
llvm-svn: 75200
2009-07-09 23:48:35 +00:00
Owen Anderson
b17f32945f Switch GlobalVariable ctors to a sane API, where *either* a context or a module is required.
llvm-svn: 75025
2009-07-08 19:03:57 +00:00
Nick Lewycky
a21d3daadc Remove the vicmp and vfcmp instructions. Because we never had a release with
these instructions, no autoupgrade or backwards compatibility support is
provided.

llvm-svn: 74991
2009-07-08 03:04:38 +00:00
Owen Anderson
5948fdf68b Push LLVMContext through GlobalVariables and IRBuilder.
llvm-svn: 74985
2009-07-08 01:26:06 +00:00
Owen Anderson
e9f9804762 LLVMContext-ify the bitcode reader.
llvm-svn: 74942
2009-07-07 20:18:58 +00:00
Devang Patel
78b7c1bfe7 !"i" is a valid MDString.
llvm-svn: 74881
2009-07-06 23:40:48 +00:00
Owen Anderson
2a15443aa8 Make the use of const with respect to LLVMContext sane. Hopefully this is the last time, for the
moment, that I will need to make far-reaching changes.

llvm-svn: 74655
2009-07-01 23:13:44 +00:00
Owen Anderson
1cf085d558 Hold the LLVMContext by reference rather than by pointer.
llvm-svn: 74640
2009-07-01 21:22:36 +00:00
Owen Anderson
6773d388aa Add a pointer to the owning LLVMContext to Module. This requires threading LLVMContext through a lot
of the bitcode reader and ASM parser APIs, as well as supporting it in all of the tools.

Patches for Clang and LLVM-GCC to follow.

llvm-svn: 74614
2009-07-01 16:58:40 +00:00
Chris Lattner
06310bf178 Fix PR4336: Iterating over use-def chains doesn't seem to be deterministic.
The problem was that BitcodeReader::materializeModule would read functions
from the bc file in densemap pointer key order (doubly non-deterministic!),
which would cause the use-def chains to be set up for globals in
non-determinstic order.  Non-determinstic use/def chains can cause 
nondeterminism in many places down-stream.

Many thanks to Julien Lerouge for putting together the pass in the PR that
shows the issue!

llvm-svn: 73470
2009-06-16 05:15:21 +00:00
Dan Gohman
a5b9645c4b Split the Add, Sub, and Mul instruction opcodes into separate
integer and floating-point opcodes, introducing
FAdd, FSub, and FMul.

For now, the AsmParser, BitcodeReader, and IRBuilder all preserve
backwards compatability, and the Core LLVM APIs preserve backwards
compatibility for IR producers. Most front-ends won't need to change
immediately.

This implements the first step of the plan outlined here:
http://nondot.org/sabre/LLVMNotes/IntegerOverflow.txt

llvm-svn: 72897
2009-06-04 22:49:04 +00:00
Nick Lewycky
cb8317dac9 Update the bitcode reader to support reading .bc files where the embedded
metadata references non-Constant values such as instructions.

llvm-svn: 72685
2009-06-01 04:42:10 +00:00
Nick Lewycky
0a8fe66a6c Fix typo in error message.
llvm-svn: 72659
2009-05-31 06:07:28 +00:00
Nick Lewycky
adbc284666 Give embedded metadata its own type instead of relying on EmptyStructTy.
llvm-svn: 72610
2009-05-30 05:06:04 +00:00
Nick Lewycky
b8f9b7a965 Make MDNode use CallbackVH. Also change MDNode to store Value* instead of
Constant* in preperation of a future change to support holding non-Constants
in an MDNode.

llvm-svn: 71407
2009-05-10 20:57:05 +00:00
Chris Lattner
277800a643 Make a major API change to BitstreamReader: split all the reading
state out of the BitstreamReader class into a BitstreamCursor class.
Doing this allows the client to have multiple cursors into the same
file, each with potentially different live block stacks and
abbreviation records.

llvm-svn: 70157
2009-04-26 20:59:02 +00:00
Chris Lattner
184f1be4a8 Add a new "available_externally" linkage type. This is intended
to support C99 inline, GNU extern inline, etc.  Related bugzilla's
include PR3517, PR3100, & PR2933.  Nothing uses this yet, but it
appears to work.

llvm-svn: 68940
2009-04-13 05:44:34 +00:00
Chris Lattner
b9e07fd297 Teach llvm-bcanalyzer to skip over the header we use on LLVM IR files.
llvm-svn: 68458
2009-04-06 20:54:32 +00:00
Nick Lewycky
49f891958f Add support for embedded metadata to LLVM. This introduces two new types of
Constant, MDString and MDNode which can only be used by globals with a name
that starts with "llvm." or as arguments to a function with the same naming
restriction.

llvm-svn: 68420
2009-04-04 07:22:01 +00:00
Chris Lattner
647cffba61 fix a serious regression I introduced in my previous patch.
llvm-svn: 68173
2009-04-01 01:43:03 +00:00
Chris Lattner
2d8cd80ee0 reimplement BitcodeReaderValueList in terms of WeakVH instead of making
it be an LLVM IR User object.

llvm-svn: 68156
2009-03-31 22:55:09 +00:00
Dale Johannesen
93eefa0043 Fix internal representation of fp80 to be the
same as a normal i80 {low64, high16} rather
than its own {high64, low16}.  A depressing number
of places know about this; I think I got them all.
Bitcode readers and writers convert back to the old
form to avoid breaking compatibility.

llvm-svn: 67562
2009-03-23 21:16:53 +00:00
Duncan Sands
4581bebf2a It makes no sense to have a ODR version of common
linkage, so remove it.

llvm-svn: 66690
2009-03-11 20:14:15 +00:00
Duncan Sands
e2881053c9 Remove the one-definition-rule version of extern_weak
linkage: this linkage type only applies to declarations,
but ODR is only relevant to globals with definitions.

llvm-svn: 66650
2009-03-11 08:08:06 +00:00
Duncan Sands
12da8ce3d2 Introduce new linkage types linkonce_odr, weak_odr, common_odr
and extern_weak_odr.  These are the same as the non-odr versions,
except that they indicate that the global will only be overridden
by an *equivalent* global.  In C, a function with weak linkage can
be overridden by a function which behaves completely differently.
This means that IP passes have to skip weak functions, since any
deductions made from the function definition might be wrong, since
the definition could be replaced by something completely different
at link time.   This is not allowed in C++, thanks to the ODR
(One-Definition-Rule): if a function is replaced by another at
link-time, then the new function must be the same as the original
function.  If a language knows that a function or other global can
only be overridden by an equivalent global, it can give it the
weak_odr linkage type, and the optimizers will understand that it
is alright to make deductions based on the function body.  The
code generators on the other hand map weak and weak_odr linkage
to the same thing.

llvm-svn: 66339
2009-03-07 15:45:40 +00:00