Commit Graph

4656 Commits

Author SHA1 Message Date
Benjamin Kramer
39b5f12dd6 InstCombine: Fix and simplify the inttoptr side too.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174438 91177308-0d34-0410-b5e6-96231b3b80d8
2013-02-05 20:22:40 +00:00
Michael Gottesman
07b884af25 Added missing newline to end of test case.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174433 91177308-0d34-0410-b5e6-96231b3b80d8
2013-02-05 19:39:44 +00:00
Benjamin Kramer
1018fa256d InstCombine: Harden code to work with vectors of pointers and simplify it a bit.
Found by running instcombine on a fabricated test case for the constant folder.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174430 91177308-0d34-0410-b5e6-96231b3b80d8
2013-02-05 19:21:56 +00:00
Benjamin Kramer
faf601ee93 ConstantFolding: Fix a crash when encoutering a truncating inttoptr.
This was introduced in r173293.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174424 91177308-0d34-0410-b5e6-96231b3b80d8
2013-02-05 19:04:36 +00:00
NAKAMURA Takumi
f5b39cd8de Formatting.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174380 91177308-0d34-0410-b5e6-96231b3b80d8
2013-02-05 15:32:16 +00:00
NAKAMURA Takumi
eec44ce834 llvm/test/Transforms/LoopVectorize/X86/vector_ptr_load_store.ll: "-debug" requires +Asserts.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174379 91177308-0d34-0410-b5e6-96231b3b80d8
2013-02-05 15:32:10 +00:00
Arnold Schwaighofer
935645b765 Loop Vectorizer: Handle pointer stores/loads in getWidestType()
In the loop vectorizer cost model, we used to ignore stores/loads of a pointer
type when computing the widest type within a loop. This meant that if we had
only stores/loads of pointers in a loop we would return a widest type of 8bits
(instead of 32 or 64 bit) and therefore a vector factor that was too big.

Now, if we see a consecutive store/load of pointers we use the size of a pointer
(from data layout).

This problem occured in SingleSource/Benchmarks/Shootout-C++/hash.cpp (reduced
test case is the first test in vector_ptr_load_store.ll).

radar://13139343

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174377 91177308-0d34-0410-b5e6-96231b3b80d8
2013-02-05 15:08:02 +00:00
Michael Gottesman
e1b6b52903 Add code to GlobalVariable.h so that global variables marked as
externally_initialized return false for hasDefiniteInitializer and
hasUniqueInitializer.

rdar://12580965.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174345 91177308-0d34-0410-b5e6-96231b3b80d8
2013-02-05 06:53:26 +00:00
David Blaikie
a8eefc7cc7 Remove the (apparently) unnecessary debug info metadata indirection.
The main lists of debug info metadata attached to the compile_unit had an extra
layer of metadata nodes they went through for no apparent reason. This patch
removes that (& still passes just as much of the GDB 7.5 test suite). If anyone
can show evidence as to why these extra metadata nodes are there I'm open to
reverting this patch & documenting why they're there.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174266 91177308-0d34-0410-b5e6-96231b3b80d8
2013-02-02 05:56:24 +00:00
Dan Gohman
03fce7074e Add a testcase for some past-the-end address subtleties.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174210 91177308-0d34-0410-b5e6-96231b3b80d8
2013-02-01 19:37:52 +00:00
Benjamin Kramer
d9f32c20da InstSimplify: stripAndComputeConstantOffsets can be called with vectors of pointers too.
Prepare it for vectors of pointers and handle simple cases. We don't handle
complicated cases because accumulateConstantOffset bails on pointer vectors.
Fixes selfhost on i386.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174179 91177308-0d34-0410-b5e6-96231b3b80d8
2013-02-01 15:21:10 +00:00
Nadav Rotem
36146afb96 Revert r174152. The shift amount may overflow and in that case this transformation is illegal.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174156 91177308-0d34-0410-b5e6-96231b3b80d8
2013-02-01 07:59:33 +00:00
Nadav Rotem
d5eb1cbee5 Optimize shift lefts of a constant by a value plus constant into a single shift.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174152 91177308-0d34-0410-b5e6-96231b3b80d8
2013-02-01 06:45:40 +00:00
Dan Gohman
fdd1eafe86 Rewrite instsimplify's handling if icmp on pointer values to remove the
remaining use of AliasAnalysis concepts such as isIdentifiedObject to
prove pointer inequality.

@external_compare in test/Transforms/InstSimplify/compare.ll shows a simple
case where a noalias argument can be equal to a global variable address, and
while AliasAnalysis can get away with saying that these pointers don't alias,
instsimplify cannot say that they are not equal.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174122 91177308-0d34-0410-b5e6-96231b3b80d8
2013-02-01 00:11:13 +00:00
Dan Gohman
ac08785eda An alloca can be equal to an argument. It can't *alias* an alloca, but it could
be equal, since there's nothing preventing a caller from correctly predicting
the stack location of an alloca.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174119 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-31 23:49:33 +00:00
Bill Wendling
169d527075 Remove the AttrBuilder form of the Attribute::get creators.
The AttrBuilder is for building a collection of attributes. The Attribute object
holds only one attribute. So it's not really useful for the Attribute object to
have a creator which takes an AttrBuilder.

This has two fallouts:

1. The AttrBuilder no longer holds its internal attributes in a bit-mask form.
2. The attributes are now ordered alphabetically (hence why the tests have changed).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174110 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-31 23:16:25 +00:00
Pekka Jaaskelainen
d72b4d321e Made the min-trip-count-switch test X86-specific to avoid
breakage with builds without X86-support.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174052 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-31 10:33:22 +00:00
Michael Gottesman
67dad63de6 Filecheckized 2x tests in SimplifyCFG and removed their date prefix to fit with current llvm style for test names.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174011 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-31 01:04:23 +00:00
Nadav Rotem
cc687faba3 InstCombine: canonicalize sext-and --> select
sext-not-and --> select.

Patch by Muhammad Tauqir Ahmad.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173901 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-30 06:35:22 +00:00
Renato Golin
0261cea689 Adding simple cast cost to ARM
Changing ARMBaseTargetMachine to return ARMTargetLowering intead of
the generic one (similar to x86 code).

Tests showing which instructions were added to cast when necessary
or cost zero when not. Downcast to 16 bits are not lowered in NEON,
so costs are not there yet.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173849 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-29 23:31:38 +00:00
Pekka Jaaskelainen
d855049576 LoopVectorize: convert TinyTripCountVectorThreshold constant
to a command line switch.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173837 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-29 21:42:08 +00:00
Bill Wendling
606c8e36df Convert getAttributes() to return an AttributeSetNode.
The AttributeSetNode contains all of the attributes. This removes one (hopefully
last) use of the Attribute class as a container of multiple attributes.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173761 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-29 03:20:31 +00:00
Chandler Carruth
455151e4f7 Re-revert r173342, without losing the compile time improvements, flat
out bug fixes, or functionality preserving refactorings.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173610 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-27 06:42:03 +00:00
Reid Kleckner
ce98f09f53 FileCheck-ify some grep tests
These tests in particular try to use escaped square brackets as an
argument to grep, which is failing for me with native win32 python.  It
appears the backslash is being lost near the CreateProcess*() call.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173506 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-25 22:11:46 +00:00
Chandler Carruth
baf868b9b8 Switch this code away from Value::isUsedInBasicBlock. That code either
loops over instructions in the basic block or the use-def list of the
value, neither of which are really efficient when repeatedly querying
about values in the same basic block.

What's more, we already know that the CondBB is small, and so we can do
a much more efficient test by counting the uses in CondBB, and seeing if
those account for all of the uses.

Finally, we shouldn't blanket fail on any such instruction, instead we
should conservatively assume that those instructions are part of the
cost.

Note that this actually fixes a bug in the pass because
isUsedInBasicBlock has a really terrible bug in it. I'll fix that in my
next commit, but the fix for it would make this code suddenly take the
compile time hit I thought it already was taking, so I wanted to go
ahead and migrate this code to a faster & better pattern.

The bug in isUsedInBasicBlock was also causing other tests to test the
wrong thing entirely: for example we weren't actually disabling
speculation for floating point operations as intended (and tested), but
the test passed because we failed to speculate them due to the
isUsedInBasicBlock failure.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173417 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-25 05:40:09 +00:00
Benjamin Kramer
d5a80c7358 Reapply chandlerc's r173342 now that the miscompile it was triggering is fixed.
Original commit message:
Plug TTI into the speculation logic, giving it a real cost interface
that can be specialized by targets.

The goal here is not to be more aggressive, but to just be more accurate
with very obvious cases. There are instructions which are known to be
truly free and which were not being modeled as such in this code -- see
the regression test which is distilled from an inner loop of zlib.

Everywhere the TTI cost model is insufficiently conservative I've added
explicit checks with FIXME comments to go add proper modelling of these
cost factors.

If this causes regressions, the likely solution is to make TTI even more
conservative in its cost estimates, but test cases will help here.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173357 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-24 16:44:25 +00:00
Benjamin Kramer
e574246489 ConstantFolding: Add a missing folding that leads to a miscompile.
We use constant folding to see if an intrinsic evaluates to the same value as a
constant that we know. If we don't take the undefinedness into account we get a
value that doesn't match the actual implementation, and miscompiled code.

This was uncovered by Chandler's simplifycfg changes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173356 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-24 16:28:28 +00:00
Chandler Carruth
eacef325c6 Revert r173342 temporarily. It appears to cause a very late miscompile
of stage2 in a bootstrap. Still investigating....

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173343 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-24 13:24:24 +00:00
Chandler Carruth
1f255419d4 Plug TTI into the speculation logic, giving it a real cost interface
that can be specialized by targets.

The goal here is not to be more aggressive, but to just be more accurate
with very obvious cases. There are instructions which are known to be
truly free and which were not being modeled as such in this code -- see
the regression test which is distilled from an inner loop of zlib.

Everywhere the TTI cost model is insufficiently conservative I've added
explicit checks with FIXME comments to go add proper modelling of these
cost factors.

If this causes regressions, the likely solution is to make TTI even more
conservative in its cost estimates, but test cases will help here.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173342 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-24 12:39:29 +00:00
Chandler Carruth
47d8f6dca5 Address a large chunk of this FIXME by accumulating the cost for
unfolded constant expressions rather than checking each one
independently.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173341 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-24 12:05:17 +00:00
Chandler Carruth
681add7a63 Switch the constant expression speculation cost evaluation away from
a cost fuction that seems both a bit ad-hoc and also poorly suited to
evaluating constant expressions.

Notably, it is missing any support for trivial expressions such as
'inttoptr'. I could fix this routine, but it isn't clear to me all of
the constraints its other users are operating under.

The core protection that seems relevant here is avoiding the formation
of a select instruction wich a further chain of select operations in
a constant expression operand. Just explicitly encode that constraint.

Also, update the comments and organization here to make it clear where
this needs to go -- this should be driven off of real cost measurements
which take into account the number of constants expressions and the
depth of the constant expression tree.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173340 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-24 11:53:01 +00:00
Benjamin Kramer
b4d201ec54 ConstantFolding: Evaluate GEP indices in the index type.
This fixes some edge cases that we would get wrong with uint64_ts.
PR14986.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173289 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-23 20:41:05 +00:00
Benjamin Kramer
028dba376a Revert "InstCombine: Clean up weird code that talks about a modulus that's long gone."
This causes crashes during the build of compiler-rt during selfhost. Add a
testcase for coverage.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173279 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-23 17:52:29 +00:00
Bill Wendling
114baee1fa Add the IR attribute 'sspstrong'.
SSPStrong applies a heuristic to insert stack protectors in these situations:

* A Protector is required for functions which contain an array, regardless of
  type or length.

* A Protector is required for functions which contain a structure/union which
  contains an array, regardless of type or length.  Note, there is no limit to
  the depth of nesting.

* A protector is required when the address of a local variable (i.e., stack
  based variable) is exposed. (E.g., such as through a local whose address is
  taken as part of the RHS of an assignment or a local whose address is taken as
  part of a function argument.)

This patch implements the SSPString attribute to be equivalent to
SSPRequired. This will change in a subsequent patch.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173230 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-23 06:41:41 +00:00
Nadav Rotem
f148c66ce4 Add support for reverse pointer induction variables. These are loops that contain pointers that count backwards.
For example, this is the hot loop in BZIP:

  do {
    m = *--p;
    *p = ( ... );
  } while (--n);



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173219 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-23 01:35:00 +00:00
Dmitri Gribenko
91df03b8f2 Tests: rewrite 'opt ... %s' to 'opt ... < %s' so that opt does not emit a ModuleID
This is done to avoid odd test failures, like the one fixed in r171243.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173163 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-22 14:39:21 +00:00
Michael Gottesman
fc8d1dd024 This test is only supposed to test that the objc-arc alias analysis
allows for gvn to perform certain optimizations. Thus the runline should
only contain -objc-arc-aa, not the full -objc-arc.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173126 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-22 04:41:11 +00:00
Andrew Trick
ea0e78af6d Remove target triple from an LSR test.
Manish already fixed this test to work with NoTTI.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173110 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-22 00:57:16 +00:00
Paul Redmond
8e528100d2 Transform (sub 0, (zext bool to A)) to (sext bool to A) and
(sub 0, (sext bool to A)) to (zext bool to A).

Patch by Muhammad Ahmad
Reviewed by Duncan Sands


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173093 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-21 21:57:20 +00:00
Nadav Rotem
0bbbc52dc8 LoopVectorizer: Implement a new heuristics for selecting the unroll factor.
We ignore the cpu frontend and focus on pipeline utilization. We do this because we
don't have a good way to estimate the loop body size at the IR level.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172964 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-20 05:24:29 +00:00
Nadav Rotem
bcdabadaf4 Change the cpu type in the test.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172963 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-20 05:20:56 +00:00
Benjamin Kramer
1af132dcf3 LoopVectorizer: Emit memory checks into their own basic block.
This separates the check for "too few elements to run the vector loop" from the
"memory overlap" check, giving a lot nicer code and allowing to skip the memory
checks when we're not going to execute the vector code anyways. We still leave
the decision of whether to emit the memory checks as branches or setccs, but it
seems to be doing a good job. If ugly code pops up we may want to emit them as
separate blocks too. Small speedup on MultiSource/Benchmarks/MallocBench/espresso.

Most of this is legwork to allow multiple bypass blocks while updating PHIs,
dominators and loop info.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172902 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-19 13:57:58 +00:00
Bill Wendling
167ede898a Reverting r171325 & r172363. This was causing a mis-compile on the self-hosted LTO build bots.
Okay, here's how to reproduce the problem:

1) Build a Release (or Release+Asserts) version of clang in the normal way.

2) Using the clang & clang++ binaries from (1), build a Release (or
   Release+Asserts) version of the same sources, but this time enable LTO ---
   specify the `-flto' flag on the command line.

3) Run the ARC migrator tests:

    $ arcmt-test --args -triple x86_64-apple-darwin10 -fsyntax-only -x objective-c++ ./src/tools/clang/test/ARCMT/cxx-rewrite.mm

You'll see that the output isn't correct (the whitespace is off).

The mis-compile is in the function `RewriteBuffer::RemoveText' in the
clang/lib/Rewrite/Core/Rewriter.cpp file. When that function and RewriteRope.cpp
are compiled with LTO and the `arcmt-test' executable is regenerated, you'll see
the error. When those files are not LTO'ed, then the output of the `arcmt-test'
is fine.

It is *really* hard to get a testcase out of this. I'll file a PR with what I
have currently.

--- Reverse-merging r172363 into '.':
U    include/llvm/Analysis/MemoryBuiltins.h
U    lib/Analysis/MemoryBuiltins.cpp

--- Reverse-merging r171325 into '.':
U    test/Transforms/InstCombine/objsize.ll
G    include/llvm/Analysis/MemoryBuiltins.h
G    lib/Analysis/MemoryBuiltins.cpp




git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172756 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-17 21:28:46 +00:00
Michael Gottesman
ac47c1bc39 Added test for r172599 which fixes bugzilla://14584,rdar://11744105.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172656 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-16 21:07:18 +00:00
Benjamin Kramer
c759dd5f83 Move test that depends on the x86 target into a target-specific directory.
Should fix the arm buildbot (which only builds the arm target).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172611 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-16 13:25:56 +00:00
Benjamin Kramer
2ce6eeb8ff Remove triple from this test, it makes it fail when X86 TTI is missing.
Without a triple opt falls back to NoTTI which comes closer to LSR's pre-TTI behavior.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172609 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-16 13:19:59 +00:00
Nadav Rotem
83d5853833 Teach InstCombine to optimize extract of a value from a vector add operation with a constant zero.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172576 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-15 23:43:14 +00:00
Shuxin Yang
a1444219b2 1. Hoist minus sign as high as possible in an attempt to reveal
some optimization opportunities (in the enclosing supper-expressions).

   rule 1. (-0.0 - X ) * Y => -0.0 - (X * Y)
     if expression "-0.0 - X" has only one reference.

   rule 2. (0.0 - X ) * Y => -0.0 - (X * Y)
     if expression "0.0 - X" has only one reference, and
        the instruction is marked "noSignedZero".

2. Eliminate negation (The compiler was already able to handle these
    opt if the 0.0s are replaced with -0.0.)

   rule 3: (0.0 - X) * (0.0 - Y) => X * Y
   rule 4: (0.0 - X) * C => X * -C
   if the expr is flagged "noSignedZero".

3. 
  Rule 5: (X*Y) * X => (X*X) * Y
   if X!=Y and the expression is flagged with "UnsafeAlgebra".

   The purpose of this transformation is two-fold:
    a) to form a power expression (of X).
    b) potentially shorten the critical path: After transformation, the
       latency of the instruction Y is amortized by the expression of X*X,
       and therefore Y is in a "less critical" position compared to what it
      was before the transformation. 

4. Remove the InstCombine code about simplifiying "X * select".
   
   The reasons are following:
    a) The "select" is somewhat architecture-dependent, therefore the
       higher level optimizers are not able to precisely predict if
       the simplification really yields any performance improvement
       or not.

    b) The "select" operator is bit complicate, and tends to obscure
       optimization opportunities. It is btter to keep it as low as
       possible in expr tree, and let CodeGen to tackle the optimization.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172551 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-15 21:09:32 +00:00
Renato Golin
08bcd5bc4d Pattern-matched variables in post-inc-icmpzero.ll
Test was failing for clang-native-arm-cortex-a9 build-bot configuration.
The reason for the failure was the test was using hardcoded names.
The attached patch fixes this failure by replacing the hard-coded variables
names with pattern-matched variable names.

Patch by Manish Verma, ARM

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172534 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-15 15:22:45 +00:00
Shuxin Yang
7d72cf892e This change is to implement following rules under the condition C_A and/or C_R
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 C_A: reassociation is allowed
 C_R: reciprocal of a constant C is appropriate, which means 
    - 1/C is exact, or 
    - reciprocal is allowed and 1/C is neither a special value nor a denormal.
 -----------------------------------------------------------------------------

 rule1:  (X/C1) / C2 => X / (C2*C1)  (if C_A)
                     => X * (1/(C2*C1))  (if C_A && C_R)
 rule 2:  X*C1 / C2 => X * (C1/C2)  if C_A
 rule 3: (X/Y)/Z = > X/(Y*Z)  (if C_A && at least one of Y and Z is symbolic value)
 rule 4: Z/(X/Y) = > (Z*Y)/X  (similar to rule3)

 rule 5: C1/(X*C2) => (C1/C2) / X (if C_A)
 rule 6: C1/(X/C2) => (C1*C2) / X (if C_A)
 rule 7: C1/(C2/X) => (C1/C2) * X (if C_A)


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172488 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-14 22:48:41 +00:00