Commit Graph

5142 Commits

Author SHA1 Message Date
Benjamin Kramer
6629210aaf Teach MemoryBuiltins and InstructionSimplify that operator new never returns NULL.
This is safe per C++11 18.6.1.1p3: [operator new returns] a non-null pointer to
suitably aligned storage (3.7.4), or else throw a bad_alloc exception. This
requirement is binding on a replacement version of this function.

Brings us a tiny bit closer to eliminating more vector push_backs.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191310 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-24 16:37:51 +00:00
Arnold Schwaighofer
4e7b015a4a Revert "LoopVectorizer: Only allow vectorization of intrinsics."
Revert 191122 - with extra checks we are allowed to vectorize math library
function calls.

Standard library indentifiers are reserved names so functions with external
linkage must not overrided them. However, functions with internal linkage can.

Therefore, we can vectorize calls to math library functions with a check for
external linkage and matching signature. This matches what we do during
SelectionDAG building.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191206 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-23 14:54:39 +00:00
Benjamin Kramer
2bbb2d4576 Expand test case a bit.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191205 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-23 14:41:35 +00:00
Benjamin Kramer
baca5334db InstSimplify: Fold equality comparisons between non-inbounds GEPs.
Overflow doesn't affect the correctness of equalities. Computing this is cheap,
we just reuse the computation for the inbounds case and try to peel of more
non-inbounds GEPs. This pattern is unlikely to ever appear in code generated by
Clang, but SCEV occasionally produces it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191200 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-23 14:16:38 +00:00
Benjamin Kramer
1ce1525ed4 SROA: Handle casts involving vectors of pointers and integer scalars.
SROA wants to convert any types of equivalent widths but it's not possible to
convert vectors of pointers to an integer scalar with a single cast. As a
workaround we add a bitcast to the corresponding int ptr type first. This type
of cast used to be an edge case but has become common with SLP vectorization.
Fixes PR17271.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191143 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-21 20:36:04 +00:00
Arnold Schwaighofer
a9baf1ecfd Reapply "SLPVectorizer: Handle more horizontal reductions (disabled)""
Reapply r191108 with a fix for a memory corruption error I introduced.  Of
course, we can't reference the scalars that we replace by vectorizing and then
call their eraseFromParent method. I only 'needed' the scalars to get the
DebugLoc. Just store the DebugLoc before actually vectorizing instead. As a nice
side effect, this also simplifies the interface between BoUpSLP and the
HorizontalReduction class to returning a value pointer (the vectorized tree
root).

radar://14607682

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191123 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-21 01:06:00 +00:00
Nadav Rotem
2ecd8c90b0 LoopVectorizer: Only allow vectorization of intrinsics. We can't know for sure that the functions 'abs' or 'round' are the functions from libm.
rdar://15012650



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191122 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-21 00:27:05 +00:00
Arnold Schwaighofer
74d3482f76 Revert "SLPVectorizer: Handle more horizontal reductions (disabled)"
This reverts commit r191108.

The horizontal.ll test case fails under libgmalloc. Thanks Shuxin for pointing
this out to me.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191121 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-21 00:06:20 +00:00
Shuxin Yang
d93e8a06b2 Resurrect r191017 " GVN proceeds in the presence of dead code" plus a fix to PR17307 & 17308.
The problem of r191017 is that when GVN fabricate a val-number for a dead instruction (in order
to make following expr-PRE happy), it forget to fabricate a leader-table entry for it as well.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191118 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-20 23:12:57 +00:00
Arnold Schwaighofer
074e489dbc SLPVectorizer: Handle more horizontal reductions (disabled)
Match reductions starting at binary operation feeding into a phi. The code
handles trees like

 r += v1 + v2 + v3 ...

and

 r += v1
 r += v2
 ...

and

 r *= v1 + v2 + ...

We currently only handle associative operations (add, fadd fast).

The code can now also handle reductions feeding into stores.

 a[i] = v1 + v2 + v3 + ...

The code is currently disabled behind the flag "-slp-vectorize-hor".  The cost
model for most architectures is not there yet.

I found one opportunity of a horizontal reduction feeding a phi in TSVC
(LoopRerolling-flt) and there are several opportunities where reductions feed
into stores.

radar://14607682

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191108 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-20 21:18:20 +00:00
Joerg Sonnenberger
2938e97562 Delete empty files.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191105 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-20 20:40:22 +00:00
Joerg Sonnenberger
fc572d87d2 Revert r191017, it results in segmentation faults in Qt.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191104 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-20 20:33:57 +00:00
Benjamin Kramer
4c332fa5a5 InstCombine: Canonicalize (gep i8* X, -(ptrtoint Y)) to (sub (ptrtoint X), (ptrtoint Y))
The GEP pattern is what SCEV expander emits for "ugly geps". The latter is what
you get for pointer subtraction in C code. The rest of instcombine already
knows how to deal with that so just canonicalize on that.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191090 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-20 14:38:44 +00:00
Shuxin Yang
b1ccfb3a54 [Fast-math] Disable "(C1/X)*C2 => (C1*C2)/X" if C1/X has multiple uses.
If "C1/X" were having multiple uses, the only benefit of this
transformation is to potentially shorten critical path. But it is at the
cost of instroducing additional div.

  The additional div may or may not incur cost depending on how div is
implemented. If it is implemented using Newton–Raphson iteration, it dosen't
seem to incur any cost (FIXME). However, if the div blocks the entire
pipeline, that sounds to be pretty expensive. Let CodeGen to take care 
this transformation.

  This patch sees 6% on a benchmark.

rdar://15032743


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191037 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-19 21:13:46 +00:00
Benjamin Kramer
bf22298093 InstCombine: Don't allow turning vector-of-pointer loads into vector-of-integer.
The code below can't handle any pointers. PR17293.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191036 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-19 20:59:04 +00:00
Shuxin Yang
1bc7315c02 GVN proceeds in the presence of dead code.
This is how it ignores the dead code:
1) When a dead branch target, say block B, is identified, all the
    blocks dominated by B is dead as well.

2) The PHIs of those blocks in dominance-frontier(B) is updated such
   that the operands corresponding to dead predecessors are replaced
   by "UndefVal".

   Using lattice's jargon, the "UndefVal" is the "Top" in essence.
   Phi node like this "phi(v1 bb1, undef xx)" will be optimized into
   "v1" if v1 is constant, or v1 is an instruction which dominate this
   PHI node.

3) When analyzing the availability of a load L, all dead mem-ops which
   L depends on disguise as a load which evaluate exactly same value as L.

4) The dead mem-ops will be materialized as "UndefVal" during code motion.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191017 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-19 17:22:51 +00:00
Chandler Carruth
89ec610f76 Name the XCore target-specific subdirectories canonically.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190940 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-18 14:08:30 +00:00
NAKAMURA Takumi
fa7b1e24e5 A couple of tests, in llvm/test/Transforms/*/xcore, are XCore-specific. They should be excluded when XCore is not built.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190938 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-18 13:56:16 +00:00
Robert Lytton
d072d1b2a3 Prevent LoopVectorizer and SLPVectorizer running if the target has no vector registers.
XCore target: Add XCoreTargetTransformInfo
This is where getNumberOfRegisters() resides, which in turn returns the
number of vector registers (=0).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190936 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-18 12:43:35 +00:00
Andrea Di Biagio
af96481135 Re-add tests from r179291 which were accidentally removed by r181177.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190934 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-18 12:06:59 +00:00
Matt Arsenault
2334b0e802 Fix a constant folding address space place I missed.
If address space 0 was smaller than the address space
in a constant inttoptr/ptrtoint pair, the wrong mask size
would be used.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190899 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-17 23:23:16 +00:00
Quentin Colombet
5383a37747 Revert the load slicing done in r190870.
To avoid regressions with bitfield optimizations, this slicing should take place
later, like ISel time.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190891 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-17 22:01:26 +00:00
Matt Arsenault
3e1c40de7f Cleanup handling of constant function casts.
Some of this code is no longer necessary since int<->ptr casts are no
longer occur as of r187444.

This also fixes handling vectors of pointers, and adds a bunch of new
testcases for vectors and address spaces.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190885 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-17 21:10:14 +00:00
Arnold Schwaighofer
3c94006742 SLPVectorizer: Don't vectorize phi nodes that use invoke values
We can't insert an insertelement after an invoke. We would have to split a
critical edge. So when we see a phi node that uses an invoke we just give up.

radar://14990770

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190871 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-17 17:03:29 +00:00
Quentin Colombet
0119f3df9c [InstCombiner] Slice a big load in two loads when the elements are next to each
other in memory.

The motivation was to get rid of truncate and shift right instructions that get
in the way of paired load or floating point load.
E.g.,
Consider the following example:
struct Complex {
  float real;
  float imm;
};

When accessing a complex, llvm was generating a 64-bits load and the imm field
was obtained by a trunc(lshr) sequence, resulting in poor code generation, at
least for x86.

The idea is to declare that two load instructions is the canonical form for
loading two arithmetic type, which are next to each other in memory.

Two scalar loads at a constant offset from each other are pretty
easy to detect for the sorts of passes that like to mess with loads. 

<rdar://problem/14477220>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190870 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-17 16:57:34 +00:00
Stepan Dyatkovskiy
80361492ae Bugfix for PR17099:
Wrong cast operation.
MergeFunctions emits Bitcast instead of pointer-to-integer operation.
Patch fixes MergeFunctions::writeThunk function. It replaces
unconditional Bitcast creation with "Value* createCast(...)" method, that
checks operand types and selects proper instruction.
See unit-test as example.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190859 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-17 09:36:11 +00:00
Krzysztof Parzyszek
892a5fdf49 Add testcase for r190631
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190807 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-16 21:24:30 +00:00
Arnold Schwaighofer
5721d2f674 Don't vectorize if there are outside loop users of the induction variable.
We would have to compute the pre increment value, either by computing it on
every loop iteration or by splitting the edge out of the loop and inserting a
computation for it there.

For now, just give up vectorizing such loops.

Fixes PR17179.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190790 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-16 16:17:24 +00:00
Chandler Carruth
3748de6e2d Remove the long, long defunct IR block placement pass.
This pass was based on the previous (essentially unused) profiling
infrastructure and the assumption that by ordering the basic blocks at
the IR level in a particular way, the correct layout would happen in the
end. This sometimes worked, and mostly didn't. It also was a really
naive implementation of the classical paper that dates from when branch
predictors were primarily directional and when loop structure wasn't
commonly available. It also didn't factor into the equation
non-fallthrough branches and other machine level details.

Anyways, for all of these reasons and more, I wrote
MachineBlockPlacement, which completely supercedes this pass. It both
uses modern profile information infrastructure, and actually works. =]

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190748 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-14 09:28:14 +00:00
Matt Arsenault
58b90b1e38 Add missing CHECK-LABEL
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190740 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-14 02:44:06 +00:00
Matt Arsenault
262dee1ebf Add test for untested path in SimplifyCFG
This case wasn't checked with a pointer condition.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190739 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-14 02:44:02 +00:00
Hal Finkel
a5d756ca39 Implement TTI getUnrollingPreferences for PowerPC
The PowerPC A2 core greatly benefits from aggressive concatenation unrolling;
use the new getUnrollingPreferences to enable this by default when targeting
the PPC A2 core.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190549 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-11 21:20:40 +00:00
Matt Arsenault
11250c1194 Teach loop-idiom about address space pointer sizes
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190491 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-11 05:09:42 +00:00
Matt Arsenault
a03e32d397 Fix missing CHECK-LABELs
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190426 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-10 19:57:05 +00:00
Eli Friedman
b1c54930cb Don't shrink atomic ops to bool in GlobalOpt.
LLVM IR doesn't currently allow atomic bool load/store operations, and the
transformation is dubious anyway because it isn't profitable on all platforms.

PR17163.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190357 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-09 22:00:13 +00:00
Quentin Colombet
2c6ef1c433 [InstCombiner] Expose opportunities to merge subtract and comparison.
Several architectures use the same instruction to perform both a comparison and
a subtract. The instruction selection framework does not allow to consider
different basic blocks to expose such fusion opportunities.

Therefore, these instructions are “merged” by CSE at MI IR level.

To increase the likelihood of CSE to apply in such situation, we reorder the
operands of the comparison, when they have the same complexity, so that they
matches the order of the most frequent subtract.
E.g.,

icmp A, B
...
sub B, A

<rdar://problem/14514580>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190352 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-09 20:56:48 +00:00
Bob Wilson
db3a9e64f8 Revert patches to add case-range support for PR1255.
The work on this project was left in an unfinished and inconsistent state.
Hopefully someone will eventually get a chance to implement this feature, but
in the meantime, it is better to put things back the way the were.  I have
left support in the bitcode reader to handle the case-range bitcode format,
so that we do not lose bitcode compatibility with the llvm 3.3 release.

This reverts the following commits: 155464, 156374, 156377, 156613, 156704,
156757, 156804 156808, 156985, 157046, 157112, 157183, 157315, 157384, 157575,
157576, 157586, 157612, 157810, 157814, 157815, 157880, 157881, 157882, 157884,
157887, 157901, 158979, 157987, 157989, 158986, 158997, 159076, 159101, 159100,
159200, 159201, 159207, 159527, 159532, 159540, 159583, 159618, 159658, 159659,
159660, 159661, 159703, 159704, 160076, 167356, 172025, 186736

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190328 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-09 19:14:35 +00:00
Manman Ren
1ed2e1fb92 Debug Info Testing: update context from empty string to null.
Context should be either null or MDNode.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190267 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-08 03:11:54 +00:00
Manman Ren
1307103dff Debug Info Testing: updated to use NULL instead of "i32 0" in a few fields.
Field 2 of DIType (Context), field 9 of DIDerivedType (TypeDerivedFrom),
field 12 of DICompositeType (ContainingType), fields 2, 7, 12 of DISubprogram
(Context, Type, ContainingType).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190205 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-06 21:03:58 +00:00
Rafael Espindola
2421572dd9 Merge these 2 tests in a single file.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189975 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-04 19:19:32 +00:00
Rafael Espindola
9718158222 Revert "Add r159136 back now that pr13124 has been fixed."
This reverts commit r189886.

I found a corner case where this optimization is not valid:

Say we have a "linkonce_odr unnamed_addr" in two translation units:
* In TU 1 this optimization kicks in and makes it hidden.
* In TU 2 it gets const merged with a constant that is *not* unnamed_addr,
  resulting in a non unnamed_addr constant with default visibility.
* The static linker rules for combining visibility them produce a hidden
  symbol, which is incorrect from the point of view of the non unnamed_addr
  constant.

The one place we can do this is when we know that the symbol is not used from
another TU in the same shared object, i.e., during LTO. I will move it there.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189954 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-04 16:09:01 +00:00
Tim Northover
0415b1810b InstCombine: allow unmasked icmps to be combined with logical ops
"(icmp op i8 A, B)" is equivalent to "(icmp op i8 (A & 0xff), B)" as a
degenerate case. Allowing this as a "masked" comparison when analysing "(icmp)
&/| (icmp)" allows us to combine them in more cases.

rdar://problem/7625728

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189931 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-04 11:57:17 +00:00
Tim Northover
7bfabdac4e InstCombine: look for masked compares with subset relation
Even in cases which aren't universally optimisable like "(A & B) != 0 && (A &
C) != 0", the masks can make one of the comparisons completely redundant. In
this case, since we've gone to the effort of spotting masked comparisons we
should combine them.

rdar://problem/7625728

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189930 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-04 11:57:13 +00:00
Rafael Espindola
79869ee59a Add r159136 back now that pr13124 has been fixed.
Original message:
If a constant or a function has linkonce_odr linkage and unnamed_addr, mark
hidden. Being linkonce_odr guarantees that it is available in every dso that
needs it. Being a constant/function with unnamed_addr guarantees that the
copies don't have to be merged.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189886 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-03 23:34:36 +00:00
Michael Gottesman
72196ab082 [objc-arc] Turn off the objc_retainBlock -> objc_retain optimization.
The reason that I am turning off this optimization is that there is an
additional case where a block can escape that has come up. Specifically, this
occurs when a block is used in a scope outside of its current scope.

This can cause a captured retainable object pointer whose life is preserved by
the objc_retainBlock to be deallocated before the block is invoked.

An example of the code needed to trigger the bug is:

----
\#import <Foundation/Foundation.h>
int main(int argc, const char * argv[]) {
  void (^somethingToDoLater)();

  {
    NSObject *obj = [NSObject new];

    somethingToDoLater = ^{
      [obj self]; // Crashes here
    };
  }

  NSLog(@"test.");

  somethingToDoLater();
  return 0;
}
----

In the next commit, I remove all the dead code that results from this.

Once I put in the fixing commit I will bring back the tests that I deleted in
this commit.

rdar://14802782.
rdar://14868830.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189869 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-03 22:40:54 +00:00
Michael Gottesman
08c560e782 [objc-arc] Move some block tests from basic.ll -> retain-block.ll and add some missing CHECK-LABELS.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189868 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-03 22:40:50 +00:00
Matt Arsenault
330943afb7 Teach InstCombineLoadCast about address spaces.
This is another one that doesn't matter much,
but uses the right GEP index types in the first
place.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189854 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-03 21:05:48 +00:00
Yi Jiang
89008539a3 In this patch we are trying to do two things:
1) If the width of vectorization list candidate is bigger than vector reg width, we will break it down to fit the vector reg.
2) We do not vectorize the width which is not power of two.

The performance result shows it will help some spec benchmarks. mesa improved 6.97% and ammp improved 1.54%. 

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189830 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-03 17:26:04 +00:00
Benjamin Kramer
bc870037f6 SimplifyLibCalls: When emitting an overloaded fp function check that it's available.
The existing code missed some edge cases when e.g. we're going to emit sqrtf but
only the availability of sqrt was checked. This happens on odd platforms like
windows.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189724 91177308-0d34-0410-b5e6-96231b3b80d8
2013-08-31 18:19:35 +00:00
Benjamin Kramer
a8517ee732 InstCombine: Check for zero shift amounts before subtracting one causing integer overflow.
PR17026. Also avoid undefined shifts and shift amounts larger than 64 bits
(those are always undef because we can't represent integer types that large).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189672 91177308-0d34-0410-b5e6-96231b3b80d8
2013-08-30 14:35:35 +00:00