If a switch instruction has a case for every possible value of its type,
with the same successor, SimplifyCFG would replace it with an icmp ult,
but the computation of the bound overflows in that case, which inverts
the test.
Patch by Jed Davis!
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rather than checking if the source and destination have the same number of
arguments and copying the attributes over directly.
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How did this ever work?
Basically, if you have a function that's inlined into the caller, it may not
have any 'call' instructions, but any 'resume' instructions it may have should
still be forwarded to the outer (caller's) landing pad. This requires that all
of the 'landingpad' instructions in the callee have their clauses merged with
the caller's outer 'landingpad' instruction (hence the bit of ugly code in the
`forwardResume' method).
Testcase in a follow commit to the test-suite repository.
<rdar://problem/13360379> & PR15555
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Nadav reported a performance regression due to the work I did to
merge the library call simplifier into instcombine [1]. The issue
is that a new LibCallSimplifier object is being created whenever
InstCombiner::runOnFunction is called. Every time a LibCallSimplifier
object is used to optimize a call it creates a hash table to map from
a function name to an object that optimizes functions of that name.
For short-lived LibCallSimplifier instances this is quite inefficient.
Especially for cases where no calls are actually simplified.
This patch fixes the issue by dropping the hash table and implementing
an explicit lookup function to correlate the function name to the object
that optimizes functions of that name. This avoids the cost of always
building and destroying the hash table in cases where the LibCallSimplifier
object is short-lived and avoids the cost of building the table when no
simplifications are actually preformed.
On a benchmark containing 100,000 calls where none of them are simplified
I noticed a 30% speedup. On a benchmark containing 100,000 calls where
all of them are simplified I noticed an 8% speedup.
[1] http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20130304/167639.html
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An invoke may require a table entry. For instance, when the function it calls
is expected to throw.
<rdar://problem/13360379>
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Fixes rdar:13349374.
Volatile loads and stores need to be preserved even if the language
standard says they are undefined. "volatile" in this context means "get
out of the way compiler, let my platform handle it".
Additionally, this is the only way I know of with llvm to write to the
first page (when hardware allows) without dropping to assembly.
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* Only apply divide bypass optimization when not optimizing for size.
* Fixed bug caused by constant for 0 value of type Int32,
used dividend type to generate the constant instead.
* For atom x86-64 apply the divide bypass to use 16-bit divides instead of
64-bit divides when operand values are small enough.
* Added lit tests for 64-bit divide bypass.
Patch by Tyler Nowicki!
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enhancement done the trivial way; by extending inputs and truncating outputs
which is addequate for targets with little or no support for integer arithmetic
on integer types less than 32 bits.
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The 'nobuiltin' attribute is applied to call sites to indicate that LLVM should
not treat the callee function as a built-in function. I.e., it shouldn't try to
replace that function with different code.
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isn't using the default calling convention. However, if the transformation is
from a call to inline IR, then the calling convention doesn't matter.
rdar://13157990
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This is a re-worked version of r174048.
Given source IR:
call void @llvm.dbg.declare(metadata !{i32* %argc.addr}, metadata !14), !dbg !15
we used to generate
call void @llvm.dbg.declare(metadata !27, metadata !28), !dbg !29!27 = metadata !{null}
With this patch, we will correctly generate
call void @llvm.dbg.declare(metadata !{i32* %argc.addr}, metadata !27), !dbg !28
Looking up %argc.addr in ValueMap will return null, since %argc.addr is already
correctly set up, we can use identity mapping.
rdar://problem/13089880
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Given source IR:
call void @llvm.dbg.declare(metadata !{i32* %argc.addr}, metadata !14), !dbg !15
we used to generate
call void @llvm.dbg.declare(metadata !27, metadata !28), !dbg !29!27 = metadata !{null}
With this patch, we will correctly generate
call void @llvm.dbg.declare(metadata !{i32* %argc.addr}, metadata !27), !dbg !28
Looking up %argc.addr in ValueMap will return null, since %argc.addr is already
correctly set up, we can use identity mapping.
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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.
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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.
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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.
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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.
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terms of cost rather than hoisting a single instruction.
This does *not* change the cost model! We still set the cost threshold
at 1 here, it's just that we track it by accumulating cost rather than
by storing an instruction.
The primary advantage is that we no longer leave no-op intrinsics in the
basic block. For example, this will now move both debug info intrinsics
and a single instruction, instead of only moving the instruction and
leaving a basic block with nothing bug debug info intrinsics in it, and
those intrinsics now no longer ordered correctly with the hoisted value.
Instead, we now splice the entire conditional basic block's instruction
sequence.
This also places the code for checking the safety of hoisting next to
the code computing the cost.
Currently, the only observable side-effect of this change is that debug
info intrinsics are no longer abandoned. I'm not sure how to craft
a test case for this, and my real goal was the refactoring, but I'll
talk to Dave or Eric about how to add a test case for this.
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Previously, the code would scan the PHI nodes and build up a small
setvector of candidate value pairs in phi nodes to go and rewrite. Once
certain the rewrite could be performed, the code walks the set, and for
each one re-scans the entire PHI node list looking for nodes to rewrite
operands.
Instead, scan the PHI nodes once to check for hazards, and then scan it
a second time to rewrite the operands to selects. No set vector, and
a max of two scans.
The only downside is that we might form identical selects, but
instcombine or anything else should fold those easily, and it seems
unlikely to happen often.
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pretty in doxygen, adding some of the details actually present in
a classic example where this matters (a loop from gzip and many other
compression algorithms), and a cautionary note about the risks inherent
in the transform. This has come up on the mailing lists recently, and
I suspect folks reading this code could benefit from going and looking
at the MI pass that can really deal with these issues.
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used uninitialized, since it fails to understand that Array is only used when
SingleValue is not, and outputs a warning. It also seems generally safer given
that the constructor is non-trivial and has plenty of early exits.
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Collections of attributes are handled via the AttributeSet class now. This
finally frees us up to make significant changes to how attributes are structured.
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Further encapsulation of the Attribute object. Don't allow direct access to the
Attribute object as an aggregate.
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Because the Attribute class is going to stop representing a collection of
attributes, limit the use of it as an aggregate in favor of using AttributeSet.
This replaces some of the uses for querying the function attributes.
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through as a reference rather than a pointer. There is always *some*
implementation of this available, so this simplifies code by not having
to test for whether it is available or not.
Further, it turns out there were piles of places where SimplifyCFG was
recursing and not passing down either TD or TTI. These are fixed to be
more pedantically consistent even though I don't have any particular
cases where it would matter.
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