Commit Graph

725 Commits

Author SHA1 Message Date
Eli Friedman 59b66883ea Representation of 'atomic load' and 'atomic store' in IR.
llvm-svn: 137170
2011-08-09 23:02:53 +00:00
Bill Wendling 49bfb12c46 Clean up the grammar for the landingpad instruction.
llvm-svn: 137042
2011-08-08 08:06:05 +00:00
Bill Wendling a503fc0494 Fix typo found by John.
llvm-svn: 137040
2011-08-08 07:58:58 +00:00
Bill Wendling c5a136103b Go back to the old definition. It's not clear that a 'resume' can be 'outlined' from the function with the landing pad for all platforms.
llvm-svn: 136799
2011-08-03 18:37:32 +00:00
Bill Wendling 0524b8d1f4 Explain how clauses are applied.
llvm-svn: 136790
2011-08-03 17:17:06 +00:00
Bill Wendling bbcb7cde34 Add the documentation for the 'landingpad' instruction. Improve the 'invoke'
instruction's documentation to reference the landingpad and resume instructions.

llvm-svn: 136729
2011-08-02 21:52:38 +00:00
Chris Lattner d3d65ab791 no need to count the terminators.
llvm-svn: 136718
2011-08-02 20:29:13 +00:00
Eli Friedman 4bc9f3c174 Minor wording tweak for memory model.
llvm-svn: 136668
2011-08-02 01:15:34 +00:00
Bill Wendling ae8b5ea838 Fix some validation errors.
llvm-svn: 136591
2011-07-31 06:47:33 +00:00
Bill Wendling 537603b35d Fix some validation errors.
llvm-svn: 136590
2011-07-31 06:45:03 +00:00
Bill Wendling f891bf8b30 Add the 'resume' instruction for the new EH rewrite.
This adds the 'resume' instruction class, IR parsing, and bitcode reading and
writing. The 'resume' instruction resumes propagation of an existing (in-flight)
exception whose unwinding was interrupted with a 'landingpad' instruction (to be
added later).

llvm-svn: 136589
2011-07-31 06:30:59 +00:00
Bill Wendling ad088e6724 Revert r136253, r136263, r136269, r136313, r136325, r136326, r136329, r136338,
r136339, r136341, r136369, r136387, r136392, r136396, r136429, r136430, r136444,
r136445, r136446, r136253 pending review.

llvm-svn: 136556
2011-07-30 05:42:50 +00:00
Eli Friedman c9a551ebed LangRef and basic memory-representation/reading/writing for 'cmpxchg' and
'atomicrmw' instructions, which allow representing all the current atomic
rmw intrinsics.

The allowed operands for these instructions are heavily restricted at the
moment; we can probably loosen it a bit, but supporting general
first-class types (where it makes sense) might get a bit complicated,
given how SelectionDAG works.

As an initial cut, these operations do not support specifying an alignment,
but it would be possible to add if we think it's useful. Specifying an
alignment lower than the natural alignment would be essentially
impossible to support on anything other than x86, but specifying a greater
alignment would be possible.  I can't think of any useful optimizations which
would use that information, but maybe someone else has ideas.

Optimizer/codegen support coming soon.

llvm-svn: 136404
2011-07-28 21:48:00 +00:00
Bill Wendling 6c923bb8d9 Merge the contents from exception-handling-rewrite to the mainline.
This adds the new instructions 'landingpad' and 'resume'.

llvm-svn: 136253
2011-07-27 20:18:04 +00:00
Bill Wendling f6a91cf41b Fix a typo.
llvm-svn: 136133
2011-07-26 20:42:28 +00:00
Bill Wendling 16b867416f Clean up the HTML here a bit.
llvm-svn: 136074
2011-07-26 10:41:15 +00:00
Eli Friedman fee02c6c13 Initial implementation of 'fence' instruction, the new C++0x-style replacement for llvm.memory.barrier.
This is just a LangRef entry and reading/writing/memory representation; optimizer+codegen support coming soon.

llvm-svn: 136009
2011-07-25 23:16:38 +00:00
Rafael Espindola 163d675e72 Add uwtable to the langref.
llvm-svn: 135913
2011-07-25 15:27:59 +00:00
Chris Lattner 2a843827a2 clarify that opaque is actually a struct type, PR10430
llvm-svn: 135861
2011-07-23 19:59:08 +00:00
Eli Friedman f12e4e914b Some LangRef tweaks, per Dan's comments.
llvm-svn: 135744
2011-07-22 03:04:45 +00:00
Eli Friedman 35b54aa148 Commit LangRef changes for LLVM concurrency model. Start of supporting C++0x memory model and atomics. See thread on llvmdev titled "Reviving the new LLVM concurrency model".
llvm-svn: 135624
2011-07-20 21:35:53 +00:00
Chris Lattner b1ed91f397 Land the long talked about "type system rewrite" patch. This
patch brings numerous advantages to LLVM.  One way to look at it
is through diffstat:
 109 files changed, 3005 insertions(+), 5906 deletions(-)

Removing almost 3K lines of code is a good thing.  Other advantages
include:

1. Value::getType() is a simple load that can be CSE'd, not a mutating
   union-find operation.
2. Types a uniqued and never move once created, defining away PATypeHolder.
3. Structs can be "named" now, and their name is part of the identity that
   uniques them.  This means that the compiler doesn't merge them structurally
   which makes the IR much less confusing.
4. Now that there is no way to get a cycle in a type graph without a named
   struct type, "upreferences" go away.
5. Type refinement is completely gone, which should make LTO much MUCH faster
   in some common cases with C++ code.
6. Types are now generally immutable, so we can use "Type *" instead 
   "const Type *" everywhere.

Downsides of this patch are that it removes some functions from the C API,
so people using those will have to upgrade to (not yet added) new API.  
"LLVM 3.0" is the right time to do this.

There are still some cleanups pending after this, this patch is large enough
as-is.

llvm-svn: 134829
2011-07-09 17:41:24 +00:00
Cameron Zwarich a32fd210c1 Use add instead of accumulate.
llvm-svn: 134752
2011-07-08 22:13:55 +00:00
Cameron Zwarich f03fa189ca Add an intrinsic and codegen support for fused multiply-accumulate. The intent
is to use this for architectures that have a native FMA instruction.

llvm-svn: 134742
2011-07-08 21:39:21 +00:00
Owen Anderson 2f37bdc392 Generalize @llvm.ctlz, @llvm.cttz, and @llvm.ctpop to work on vectors of integers, and fix the one optimization pass that I'm aware of that needs updating for this. At least one current target, ARM NEON, can implement these operations on vectors directly.
llvm-svn: 134265
2011-07-01 21:52:38 +00:00
Evan Cheng 0ac49c6eab Add missing operand. rdar://9694169
llvm-svn: 134078
2011-06-29 17:14:00 +00:00
Dan Gohman 8bd11f1834 Document nonlazybind.
llvm-svn: 133160
2011-06-16 16:03:13 +00:00
Bruno Cardoso Lopes dc9ff3a4b1 Add one more argument to the prefetch intrinsic to indicate whether it's a data
or instruction cache access. Update the targets to match it and also teach
autoupgrade.

llvm-svn: 132976
2011-06-14 04:58:37 +00:00
Dan Gohman e635c529a0 Fix copy+pastos.
llvm-svn: 132168
2011-05-27 00:36:31 +00:00
Dan Gohman 911fa9084c Document llvm.exp and llvm.pow.
llvm-svn: 131921
2011-05-23 21:13:03 +00:00
Chris Lattner c2e8540216 insertvalue takes a variable number of arguments, document this, fixing PR9935.
llvm-svn: 131850
2011-05-22 07:18:08 +00:00
Nick Lewycky 9c876bf937 Fix errors in this llvm ir example.
llvm-svn: 131416
2011-05-16 19:29:30 +00:00
NAKAMURA Takumi aa3d6242cf docs: Introduce cascading style <div> and <p> continued on <h[2-5]>.
<h2>Section Example</h2>
<div> <!-- h2+div is applied -->
<p>Section preamble.</p>

<h3>Subsection Example</h3>
<p> <!-- h3+p is applied -->
Subsection body
</p>

<!-- End of section body -->
</div>

FIXME: Care H5 better.
llvm-svn: 130040
2011-04-23 00:30:22 +00:00
NAKAMURA Takumi fc8d930f6e docs: Use <Hn> as Heading elements instead of <DIV class="doc_foo">.
H1 ... doc_title
H2 ... doc_section
H3 ... doc_subsection
H4 ... doc_subsubsection

llvm-svn: 129736
2011-04-18 23:59:50 +00:00
Chris Lattner 0ab5e2cded Fix a ton of comment typos found by codespell. Patch by
Luis Felipe Strano Moraes!

llvm-svn: 129558
2011-04-15 05:18:47 +00:00
Dan Gohman c8454ee995 Fix a hole in the definition of "dependence" used by trap values. Trap
values are also transmitted through branches which cause side effects to
be skipped altogether.

llvm-svn: 129404
2011-04-12 23:05:59 +00:00
NAKAMURA Takumi ca46f5a3b5 docs: Canonicalize URLs.
llvm-svn: 129181
2011-04-09 02:13:37 +00:00
Nick Lewycky 9feca67182 Pick better examples. "fpext float 3.1415 to double" won't parse because 3.1415
isn't an exact float. Also "fpext float 1.0 to float" is invalid IR because
it's not performing an extension.

llvm-svn: 128647
2011-03-31 18:20:19 +00:00
Cameron Zwarich 341c36dc8b Change the signext language in LangRef to closer match zeroext.
llvm-svn: 127808
2011-03-17 14:21:58 +00:00
Cameron Zwarich ac106273d4 The x86-64 ABI says that a bool is only guaranteed to be sign-extended to a byte
rather than an int. Thankfully, this only causes LLVM to miss optimizations, not
generate incorrect code.

This just fixes the zext at the return. We still insert an i32 ZextAssert when
reading a function's arguments, but it is followed by a truncate and another i8
ZextAssert so it is not optimized.

llvm-svn: 127766
2011-03-16 22:20:18 +00:00
Duncan Sands 2769c6e0dc Clarify that the result of an srem is only guaranteed to have the same sign as the
left-hand-side if the result is non-zero.

llvm-svn: 127156
2011-03-07 09:12:24 +00:00
Bill Wendling c0e1067e4d Small cleanup.
llvm-svn: 126821
2011-03-02 02:17:11 +00:00
Nadav Rotem 502f1b943f Enable support for vector sext and trunc:
Limit the folding of any_ext and sext  into the load operation to scalars.
Limit the active-bits trunc optimization to scalars.
Document vector trunc and vector sext in LangRef.

Similar to commit 126080 (for enabling zext).

llvm-svn: 126424
2011-02-24 21:01:34 +00:00
Nadav Rotem 25f2ac948b Fix 9267; Add vector zext support.
The DAGCombiner folds the zext into complex load instructions. This patch
prevents this optimization on vectors since none of the supported targets
knows how to perform load+vector_zext in one instruction.

llvm-svn: 126080
2011-02-20 12:37:50 +00:00
Chris Lattner f10dfdc77a fix typo
llvm-svn: 125192
2011-02-09 16:44:44 +00:00
Chris Lattner a676c0fc77 implement .ll and .bc support for nsw/nuw on shl and exact on lshr/ashr.
Factor some code better.

llvm-svn: 125006
2011-02-07 16:40:21 +00:00
Chris Lattner 35315d065b enhance vmcore to know that udiv's can be exact, and add a trivial
instcombine xform to exercise this.

Nothing forms exact udivs yet though.  This is progress on PR8862

llvm-svn: 124992
2011-02-06 21:44:57 +00:00
Nick Lewycky fea7ddc735 Most browsers eliminate whitespace between anchor tags. Force whitespace with
&nbsp; so that the code reads properly.

llvm-svn: 124514
2011-01-29 01:09:53 +00:00
Rafael Espindola f1ed781aea Add a clarification about merging constants with and without unnamed_addr.
llvm-svn: 123530
2011-01-15 08:20:57 +00:00
Rafael Espindola 45e6c195d7 First step in fixing PR8927:
Add a unnamed_addr bit to global variables and functions. This will be used
to indicate that the address is not significant and therefore the constant
or function can be merged with others.

If an optimization pass can show that an address is not used, it can set this.

Examples of things that can have this set by the FE are globals created to
hold string literals and C++ constructors.

Adding unnamed_addr to a non-const global should have no effect unless
an optimization can transform that global into a constant.

Aliases are not allowed to have unnamed_addr since I couldn't figure
out any use for it.

llvm-svn: 123063
2011-01-08 16:42:36 +00:00
Tobias Grosser 4c8c95b099 Integers are primitive types. Update the documentation to state this
This was done for label, void, floating point, x86mmx, metadata,
just not integer.

llvm-svn: 122606
2010-12-28 20:29:31 +00:00
Frits van Bommel 7cf63ace18 Clarify some of the differences between indexing with getelementptr and indexing with insertvalue/extractvalue.
llvm-svn: 120957
2010-12-05 20:54:38 +00:00
Nick Lewycky 2965d3e3cd Make @llvm.invariant.start not be readonly, so that it has side-effects. This
unbreaks test/Transforms/InstCombine/invariant.ll which was broken by r120382.
This is a fix-forward to do what I think Chris intended.

llvm-svn: 120388
2010-11-30 04:13:41 +00:00
Chris Lattner d78dbee431 a byval argument without an align can have an arbitrary alignment
requirement on the input pointer.

llvm-svn: 119914
2010-11-20 23:49:06 +00:00
Chris Lattner 79ffdc7581 With the newly simplified SourceMgr interfaces and the generalized
SrcMgrDiagHandler, we can improve clang diagnostics for inline asm:
instead of reporting them on a source line of the original line,
we can report it on the correct line wherever the string literal came
from. For something like this:

void foo() {
  asm("push %rax\n"
      ".code32\n");
}

we used to get this: (note that the line in t.c isn't helpful)

t.c:4:7: error: warning: ignoring directive for now
  asm("push %rax\n"
      ^
<inline asm>:2:1: note: instantiated into assembly here
.code32
^

now we get:

t.c:5:8: error: warning: ignoring directive for now
      ".code32\n"
       ^
<inline asm>:2:1: note: instantiated into assembly here
.code32
^

Note that we're pointing to line 5 properly now.

llvm-svn: 119488
2010-11-17 08:20:42 +00:00
Bill Wendling 6bbe0912c3 Random cleanups and format changes.
llvm-svn: 117428
2010-10-27 01:07:41 +00:00
Charles Davis 742052526a Make the description of the hotpatch attribute even more generic. Spotted by
Michael Spencer.

llvm-svn: 117286
2010-10-25 19:07:39 +00:00
Charles Davis 1b2d372b9f Make hotpatch attribute description a little less Wintel-specific.
llvm-svn: 117267
2010-10-25 16:29:03 +00:00
Charles Davis 22fe18625d Add a new 'hotpatch' attribute. This attribute will insert a two-byte no-op
instruction at the beginning of each function that has the attribute, allowing
the function to be easily hooked and/or patched.

llvm-svn: 117264
2010-10-25 15:37:09 +00:00
Chris Lattner f11031a68c clarify that zero sized vectors are illegal, PR8340
llvm-svn: 116167
2010-10-10 18:20:35 +00:00
Dale Johannesen b1f0ff1d66 Fix pasto.
llvm-svn: 115261
2010-10-01 01:07:02 +00:00
Dale Johannesen 33e5c354e5 Add some doc for the x86mmx type.
llvm-svn: 115255
2010-10-01 00:48:59 +00:00
Chris Lattner 13ee795c42 remove unions from LLVM IR. They are severely buggy and not
being actively maintained, improved, or extended.

llvm-svn: 112356
2010-08-28 04:09:24 +00:00
Bill Wendling 578ee4070c Create the new linker type "linker_private_weak_def_auto".
It's similar to "linker_private_weak", but it's known that the address of the
object is not taken. For instance, functions that had an inline definition, but
the compiler decided not to inline it. Note, unlike linker_private and
linker_private_weak, linker_private_weak_def_auto may have only default
visibility.  The symbols are removed by the linker from the final linked image
(executable or dynamic library).

llvm-svn: 111684
2010-08-20 22:05:50 +00:00
Chris Lattner 249b976ed2 fix a broken link
llvm-svn: 111326
2010-08-17 23:26:04 +00:00
Chris Lattner 54a7be757b add some &nbsp;'s to a pre to avoid newlines being eaten
and the formatting being thrown off.  I admit to not knowing
what is going on here.

llvm-svn: 111249
2010-08-17 17:13:42 +00:00
John Criswell ad05ae483f Grammar cop pullover: Corrected and improved some grammar in the description of
the llvm.memset() intrinsic family.
No content changes.

llvm-svn: 109863
2010-07-30 16:30:28 +00:00
Dan Gohman 093cb79d4b Disallow null as a named metadata operand.
Make MDNode::destroy private.
Fix the one thing that used MDNode::destroy, outside of MDNode itself.

One should never delete or destroy an MDNode explicitly. MDNodes
implicitly go away when there are no references to them (implementation
details aside).

llvm-svn: 109028
2010-07-21 18:54:18 +00:00
Dan Gohman 58cd65f2fe Fix the Named Metadata example to make it clear which specific
construct is the named metadata.

llvm-svn: 108263
2010-07-13 19:48:13 +00:00
Benjamin Kramer 79698be162 HTML cleanup and validation.
llvm-svn: 108239
2010-07-13 12:26:09 +00:00
Duncan Sands a522e563a8 When doing sext/zext of constants, the target type must be strictly
wider than the source type.  Correct LangRef.

llvm-svn: 108238
2010-07-13 12:06:14 +00:00
Dan Gohman e501ff7cc6 sdiv overflow is outright undefined behavior, with or without the
'exact' keyword. Thanks to nlewycky for pointing this out!

llvm-svn: 108064
2010-07-11 00:08:34 +00:00
John McCall 72ed8908ee Closing tags start with slashes.
llvm-svn: 107699
2010-07-06 21:07:14 +00:00
Chris Lattner 5eff9ca26e minor typo
llvm-svn: 107696
2010-07-06 20:51:35 +00:00
Nick Lewycky 14b58dac8d Alphabetize the list of function parameters.
llvm-svn: 107680
2010-07-06 18:24:09 +00:00
Dan Gohman 6c858db40c Note the relationship between C99 restrict and LLVM noalias, and
clarify a few other things.

llvm-svn: 107659
2010-07-06 15:26:33 +00:00
Dan Gohman de25629e4f Describe which dependencies are relevant to noalias, and document how
AliasAnalyses have the choice to respect noalias.

llvm-svn: 107544
2010-07-02 23:46:54 +00:00
Dan Gohman 3770af5852 Add some html anchors, to allow attributes to be linked to directly.
llvm-svn: 107538
2010-07-02 23:18:08 +00:00
Dan Gohman df12d08b8e Reword the definition of the noalias attribute. The intention is for
the noalias argument on function attributes be usable to model the
C99 restrict keyword on arguments, and to allow AliasAnalysis to
consider a noalias-attributed argument to be an "identified object".

To support this, refactor a new "based on" concept out of the current
pointer aliasing "associated" concept. This "based on" concept is very
similar to (though it is not identical with) the "based on" concept
in C99.

Also, reword the definition of NoAlias to more closely describe the
concept that the optimizer uses.

llvm-svn: 107495
2010-07-02 18:41:32 +00:00
Bill Wendling 03bcd6ecc8 Implement the "linker_private_weak" linkage type. This will be used for
Objective-C metadata types which should be marked as "weak", but which the
linker will remove upon final linkage. However, this linkage isn't specific to
Objective-C.

For example, the "objc_msgSend_fixup_alloc" symbol is defined like this:

      .globl l_objc_msgSend_fixup_alloc
      .weak_definition l_objc_msgSend_fixup_alloc
      .section __DATA, __objc_msgrefs, coalesced
      .align 3
l_objc_msgSend_fixup_alloc:
       .quad   _objc_msgSend_fixup
       .quad   L_OBJC_METH_VAR_NAME_1

This is different from the "linker_private" linkage type, because it can't have
the metadata defined with ".weak_definition".

Currently only supported on Darwin platforms.

llvm-svn: 107433
2010-07-01 21:55:59 +00:00
Bill Wendling 3632171750 Revert r107205 and r107207.
llvm-svn: 107215
2010-06-29 22:34:52 +00:00
Bill Wendling 7d7a50a0ae Improve explanation.
llvm-svn: 107207
2010-06-29 21:41:58 +00:00
Bill Wendling 1767723dbe Introducing the "linker_weak" linkage type. This will be used for Objective-C
metadata types which should be marked as "weak", but which the linker will
remove upon final linkage. For example, the "objc_msgSend_fixup_alloc" symbol is
defined like this:

       .globl l_objc_msgSend_fixup_alloc
       .weak_definition l_objc_msgSend_fixup_alloc
       .section __DATA, __objc_msgrefs, coalesced
       .align 3
l_objc_msgSend_fixup_alloc:
        .quad   _objc_msgSend_fixup
        .quad   L_OBJC_METH_VAR_NAME_1

This is different from the "linker_private" linkage type, because it can't have
the metadata defined with ".weak_definition".

llvm-svn: 107205
2010-06-29 21:24:00 +00:00
Dan Gohman 4eb4719432 Minor clarification.
llvm-svn: 106234
2010-06-17 19:23:50 +00:00
Nick Lewycky 9ab9a7fb29 Document aggregate operation constant expressions.
llvm-svn: 105098
2010-05-29 06:44:15 +00:00
Dale Johannesen ce52285c38 Fix Data Layout description of floating point.
llvm-svn: 104993
2010-05-28 18:54:47 +00:00
Dan Gohman aabfdb39af Fix more whitespace to be consistent with AsmPrinter.
llvm-svn: 104963
2010-05-28 17:13:49 +00:00
Dan Gohman d6a6f61fdb Fix whitespace to be more consistent with AsmPrinter's style.
llvm-svn: 104962
2010-05-28 17:07:41 +00:00
Dan Gohman 2140a74979 Eliminate the restriction that the array size in an alloca must be i32.
This will help reduce the amount of casting required on 64-bit targets.

llvm-svn: 104911
2010-05-28 01:14:11 +00:00
Dan Gohman e58f7b3c76 Fix a missing quote.
llvm-svn: 104750
2010-05-26 21:56:15 +00:00
mike-m f375e9a092 Revert r103213. It broke several sections of live website.
llvm-svn: 103219
2010-05-07 00:28:04 +00:00
mike-m e08af303a6 Overhauled llvm/clang docs builds. Closes PR6613.
NOTE: 2nd part changeset for cfe trunk to follow.

*** PRE-PATCH ISSUES ADDRESSED

- clang api docs fail build from objdir
- clang/llvm api docs collide in install PREFIX/
- clang/llvm main docs collide in install
- clang/llvm main docs have full of hard coded destination
  assumptions and make use of absolute root in static html files;
  namely CommandGuide tools hard codes a website destination
  for cross references and some html cross references assume
  website root paths

*** IMPROVEMENTS

- bumped Doxygen from 1.4.x -> 1.6.3
- splits llvm/clang docs into 'main' and 'api' (doxygen) build trees
- provide consistent, reliable doc builds for both main+api docs
- support buid vs. install vs. website intentions
- support objdir builds
- document targets with 'make help'
- correct clean and uninstall operations
- use recursive dir delete only where absolutely necessary
- added call function fn.RMRF which safeguards against botched 'rm -rf';
  if any target (or any variable is evaluated) which attempts
  to remove any dirs which match a hard-coded 'safelist', a verbose
  error will be printed and make will error-stop.

llvm-svn: 103213
2010-05-06 23:45:43 +00:00
Chris Lattner 966a382ae7 Fix some ..'s
llvm-svn: 103134
2010-05-05 23:29:09 +00:00
Dan Gohman 3513ea5c1a Update this comment to note its relationship with the "happens-before"
concept in the proposed memory model changes.

llvm-svn: 102911
2010-05-03 14:59:34 +00:00
Dan Gohman a9601bb6fb Delete this comment. The behavior of struct loads and stores with
respect to padding bytes isn't something that the dependence text
needs to spell out.

llvm-svn: 102910
2010-05-03 14:58:14 +00:00
Dan Gohman 7292a759b4 Describe invoke instruction dependencies. Generalize the text for
terminator instructions so that it applies to all terminators with
multiple successors, including invoke.

llvm-svn: 102909
2010-05-03 14:55:22 +00:00
Dan Gohman ac355aaf9e Say "operations" instead of "instructions", as nsw can be applied to
constant expressions as well as instructions.

llvm-svn: 102908
2010-05-03 14:51:43 +00:00
David Chisnall b492b81a94 Fixed @ctor / @dtor the wrong way around in last commit.
llvm-svn: 102741
2010-04-30 19:27:35 +00:00
David Chisnall a9d4a6fb28 Added a brief explanation of @llvm.global_{c,d}tors.
llvm-svn: 102740
2010-04-30 19:23:49 +00:00
Dan Gohman 2f1ae06c45 Rewrite the section on trap values to contain a generic description
of dependence and define trap values in terms of dependence, instead
of trying to cover the concept with a flurry of ad-hoc rules.

The dependence model isn't complete yet, but it's already much more
rigorous than the description it replaces.

llvm-svn: 102479
2010-04-28 00:49:41 +00:00