In the future, AttributeWithIndex won't be used anymore. Besides, it exposes the
internals of the AttributeSet to outside users, which isn't goodness.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173601 91177308-0d34-0410-b5e6-96231b3b80d8
In the future, AttributeWithIndex won't be used anymore. Besides, it exposes the
internals of the AttributeSet to outside users, which isn't goodness.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173600 91177308-0d34-0410-b5e6-96231b3b80d8
The 'getSlot' function and its ilk allow introspection into the AttributeSet
class. However, that class should be opaque. Allow access through accessor
methods instead.
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Only for integers, pointers, and vectors of those. No floats.
Instrumentation seems very heavy, and may need to be replaced
with some approximation in the future.
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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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This does the right thing unless the multiplication overflows, but the old code
didn't handle that case either.
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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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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.
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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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The method PerformCodePlacement was doing too much (i.e. 3x loops, lots of
different checking). This refactoring separates the analysis section of the
method into a separate function while leaving the actual code placement and
analysis preparation in PerformCodePlacement.
*NOTE* Really this part of ObjCARC should be refactored out of the main pass
class into its own seperate class/struct. But, it is not time to make that
change yet though (don't want to make such an invasive change without fixing all
of the bugs first).
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Use the AttributeSet when we're talking about more than one attribute. Add a
function that adds a single attribute. No functionality change intended.
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generic function calls and intrinsics. This is somewhat overlapping with
an existing intrinsic cost method, but that one seems targetted at
vector intrinsics. I'll merge them or separate their names and use cases
in a separate commit.
This sinks the test of 'callIsSmall' down into TTI where targets can
control it. The whole thing feels very hack-ish to me though. I've left
a FIXME comment about the fundamental design problem this presents. It
isn't yet clear to me what the users of this function *really* care
about. I'll have to do more analysis to figure that out. Putting this
here at least provides it access to proper analysis pass tools and other
such. It also allows us to more cleanly implement the baseline cost
interfaces in TTI.
With this commit, it is now theoretically possible to simplify much of
the inline cost analysis's handling of calls by calling through to this
interface. That conversion will have to happen in subsequent commits as
it requires more extensive restructuring of the inline cost analysis.
The CodeMetrics class is now really only in the business of running over
a block of code and aggregating the metrics on that block of code, with
the actual cost evaluation done entirely in terms of TTI.
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This is more code to isolate the use of the Attribute class to that of just
holding one attribute instead of a collection of attributes.
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is free. The whole CodeMetrics API should probably be reworked more, but
this is enough to allow deleting the duplicate code there for computing
whether an instruction is free.
All of the passes using this have been updated to pull in TTI and hand
it to the CodeMetrics stuff. Further, a dead CodeMetrics API
(analyzeFunction) is nuked for lack of users.
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a dynamic analysis done on each call to the routine. However, now it can
use the standard pass infrastructure to reference other analyses,
instead of a silly setter method. This will become more interesting as
I teach it about more analysis passes.
This updates the two inliner passes to use the inline cost analysis.
Doing so highlights how utterly redundant these two passes are. Either
we should find a cheaper way to do always inlining, or we should merge
the two and just fiddle with the thresholds to get the desired behavior.
I'm leaning increasingly toward the latter as it would also remove the
Inliner sub-class split.
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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.
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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.
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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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Specifically according to the semantics of ARC -fno-objc-arc-exception simply
states that it is expected that the unwind path out of a call *MAY* not release
objects. Thus we can have the situation where a release gets moved into a catch
block which we ignore when we remove a retain/release pair resulting in (even
though we assume the program is exiting anyways) the cleanup code path
potentially blowing up before program exit.
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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.
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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)
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case, but looking at the diff this was an obviously unintended change.
Thanks for the careful review Bill! =]
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The reason that this occurs is that tail calling objc_autorelease eventually
tail calls -[NSObject autorelease] which supports fast autorelease. This can
cause us to violate the semantic gaurantees of __autoreleasing variables that
assignment to an __autoreleasing variables always yields an object that is
placed into the innermost autorelease pool.
The fix included in this patch works by:
1. In the peephole optimization function OptimizeIndividualFunctions, always
remove tail call from objc_autorelease.
2. Whenever we convert to/from an objc_autorelease, set/unset the tail call
keyword as appropriate.
*NOTE* I also handled the case where objc_autorelease is converted in
OptimizeReturns to an autoreleaseRV which still violates the ARC semantics. I
will be removing that in a later patch and I wanted to make sure that the tree
is in a consistent state vis-a-vis ARC always.
Additionally some test cases are provided and all tests that have tail call marked
objc_autorelease keywords have been modified so that tail call has been removed.
*NOTE* One test fails due to a separate bug that I am going to commit soon. Thus
I marked the check line TMP: instead of CHECK: so make check does not fail.
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Specifically:
1. Added a missing new line when we emit a debug message saying that we are marking a global variable as constant.
2. Added debug messages that describe what is occuring when GlobalOpt is evaluating a block/function.
3. Added a debug message that says what specific constructor is being evaluated.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172247 91177308-0d34-0410-b5e6-96231b3b80d8
We don't have a detailed analysis on which values are vectorized and which stay scalars in the vectorized loop so we use
another method. We look at reduction variables, loads and stores, which are the only ways to get information in and out
of loop iterations. If the data types are extended and truncated then the cost model will catch the cost of the vector
zext/sext/trunc operations.
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The root cause is mistakenly taking for granted that
"dyn_cast<Instruction>(a-Value)"
return a non-NULL instruction.
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