allowed to canonicalize return values).
Add a test that checks if return value and function attributes are not removed.
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return values that are still (partially) live. Instead of updating all uses of
a call instruction after removing some elements, it now just rebuilds the
original struct (With undef gaps where the unused values were) and leaves it to
instcombine to clean this up.
The added testcase still fails currently, but this is due to instcombine which
isn't good enough yet. I will fix that part next.
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was using the algorithm for folding unsigned comparisons which is
completely wrong. This has been broken since the signless types change.
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This cause a regression in InstCombine/JavaCompare, which was doing the right
thing on accident. To handle the missed case, generalize the comparisons based
on masked bits a little bit to handle comparisons against the max value. For
example, we can now xform (slt i32 (and X, 4), 4) -> (setne i32 (and X, 4), 4)
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Rewrite the DeadArgumentElimination pass, to use a more explicit tracking of
dependencies between return values and/or arguments. Also make the handling of
arguments and return values the same.
The pass now looks properly inside returned structs, but only at the first
level (ie, not inside nested structs).
This version fixed a few more bugs and was cleaned up a bit. It now passes all
of LLVM's testing, and should still pass SPEC2006. There is still a minor bug
with regard to returning nested structs. Since there is currently nothing that
emits such IR, I will fix that in a seperate commit (partly because it requires
a non-trivial fix).
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1) evaluate [v]fcmp true/false with undefs to true or false instead
of undef.
2) fix vector comparisons with undef to return a vector result instead
of i1
3) fix vector comparisons with evaluatable results to return vector
true/false instead of i1 true/false (PR2529)
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in the presence of out-of-loop users of in-loop values and the trip
count is not a known multiple of the unroll count, and to be a bit
simpler overall. This fixes PR2253.
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structures. Its default threshold is to promote things that are
smaller than 128 bytes, which is sane. However, it is not sane
to do this for things that turn into 128 *registers*. Add a cap
on the number of registers introduced, defaulting to 128/4=32.
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This is a fixed version that no longer uses multimap::equal_range, which
resulted in a pointer invalidation problem.
Also, DAE::InspectedFunctions was not really necessary, so it got removed.
Lastly, this version no longer applies the extra arg hack on functions who did
not have any arguments to start with.
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dependencies between return values and/or arguments. Also make the handling of
arguments and return values the same.
The pass now looks properly inside returned structs, but only at the first
level (ie, not inside nested structs).
Also add a testcase for testing various variations of (multiple) dead rerturn
values.
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time. Sorry for the trouble!
This time, also add a testcase, which I should have done in the first place...
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individually.
Also learn IPConstProp how returning first class aggregates work, in addition
to old style multiple return instructions.
Modify the return-constants testscase to confirm this behaviour.
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when changing the stride of a comparison so that it's slightly
more precise, by having it scan the instruction list to determine
if there is a use of the condition after the point where the
condition will be inserted.
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take into account the instrucion pointed by InsertPt. Thanks to it,
returning the new value of InsertPt to the InsertBinop() caller can be
avoided. The bug was, actually, in visitAddRecExpr() method which wasn't
correctly handling changes of InsertPt. There shouldn't be any
performance regression, as -gvn pass (run after -indvars) removes any
redundant binops.
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cases quoting of <{ didn't work out, so I changed the grep to check for }>
instead.
This fixes 7 testcases that were not properly running before.
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Also, use > %t instead of -o %t for output in one test since that also works
when %t already exists.
This fixes 6 testcases.
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work and how to replace them into individual values. Also, when trying to
replace an aggregrate that is used by load or store with a single (large)
integer, don't crash (but don't replace the aggregrate either).
Also adds a testcase for both structs and arrays.
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the conditions for performing the transform when only the
function declaration is available: no longer allow turning
i32 into i64 for example. Only allow changing between
pointer types, and between pointer types and integers of
the same size. For return values ptr -> intptr was already
allowed; I added ptr -> ptr and intptr -> ptr while there.
As shown by a recent objc testcase, changing the way
parameters/return values are passed can be fatal when calling
code written in assembler that directly manipulates call
arguments and return values unless the transform has no
impact on the way they are passed at the codegen level.
While it is possible to imagine an ABI that treats integers
of pointer size differently to pointers, I don't think LLVM
supports any so the transform should now be safe while still
being useful.
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the one case that ADCE catches that normal DCE doesn't: non-induction variable
loop computations.
This implementation handles this problem without using postdominators.
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Analysis/ConstantFolding to fold ConstantExpr's, then make instcombine use it
to try to use targetdata to fold constant expressions on void instructions.
Also extend the icmp(inttoptr, inttoptr) folding to handle the case where
int size != ptr size.
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The SimplifyCFG pass looks at basic blocks that contain only phi nodes,
followed by an unconditional branch. In a lot of cases, such a block (BB) can
be merged into their successor (Succ).
This merging is performed by TryToSimplifyUncondBranchFromEmptyBlock. It does
this by taking all phi nodes in the succesor block Succ and expanding them to
include the predecessors of BB. Furthermore, any phi nodes in BB are moved to
Succ and expanded to include the predecessors of Succ as well.
Before attempting this merge, CanPropagatePredecessorsForPHIs checks to see if
all phi nodes can be properly merged. All functional changes are made to
this function, only comments were updated in
TryToSimplifyUncondBranchFromEmptyBlock.
In the original code, CanPropagatePredecessorsForPHIs looks quite convoluted
and more like stack of checks added to handle different kinds of situations
than a comprehensive check. In particular the first check in the function did
some value checking for the case that BB and Succ have a common predecessor,
while the last check in the function simply rejected all cases where BB and
Succ have a common predecessor. The first check was still useful in the case
that BB did not contain any phi nodes at all, though, so it was not completely
useless.
Now, CanPropagatePredecessorsForPHIs is restructured to to look a lot more
similar to the code that actually performs the merge. Both functions now look
at the same phi nodes in about the same order. Any conflicts (phi nodes with
different values for the same source) that could arise from merging or moving
phi nodes are detected. If no conflicts are found, the merge can happen.
Apart from only restructuring the checks, two main changes in functionality
happened.
Firstly, the old code rejected blocks with common predecessors in most cases.
The new code performs some extra checks so common predecessors can be handled
in a lot of cases. Wherever common predecessors still pose problems, the
blocks are left untouched.
Secondly, the old code rejected the merge when values (phi nodes) from BB were
used in any other place than Succ. However, it does not seem that there is any
situation that would require this check. Even more, this can be proven.
Consider that BB is a block containing of a single phi node "%a" and a branch
to Succ. Now, since the definition of %a will dominate all of its uses, BB
will dominate all blocks that use %a. Furthermore, since the branch from BB to
Succ is unconditional, Succ will also dominate all uses of %a.
Now, assume that one predecessor of Succ is not dominated by BB (and thus not
dominated by Succ). Since at least one use of %a (but in reality all of them)
is reachable from Succ, you could end up at a use of %a without passing
through it's definition in BB (by coming from X through Succ). This is a
contradiction, meaning that our original assumption is wrong. Thus, all
predecessors of Succ must also be dominated by BB (and thus also by Succ).
This means that moving the phi node %a from BB to Succ does not pose any
problems when the two blocks are merged, and any use checks are not needed.
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and/or to handle more cases (such as this add-sitofp.ll testcase), and
port it to selectiondag's ComputeNumSignBits.
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to accurately represent the integer. This triggers 9 times in 471.omnetpp,
though 8 of those seem to be inlined from the same place.
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type and the other operand is a constant into integer comparisons.
This happens surprisingly frequently (e.g. 10 times in 471.omnetpp),
which are things like this:
%tmp8283 = sitofp i32 %tmp82 to double
%tmp1013 = fcmp ult double %tmp8283, 0.0
Clearly comparing tmp82 against i32 0 is cheaper here.
this also triggers 8 times in gobmk, including this one:
%tmp375376 = sitofp i32 %tmp375 to double
%tmp377 = fcmp ogt double %tmp375376, 8.150000e+01
which is comparing an integer against 81.5 :).
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intersecting bits. This triggers all over the place, for example in lencode,
with adds of stuff like:
%tmp580 = mul i32 %tmp579, 2
%tmp582 = and i32 %b8, 1
and
%tmp28 = shl i32 %abs.i, 1
%sign.0 = select i1 %tmp23, i32 1, i32 0
and
%tmp344 = shl i32 %tmp343, 2
%tmp346 = and i32 %tmp96, 3
etc.
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is bitcast to return a floating point value. The result of the instruction may
not be used by the program afterwards, and LLVM will happily remove all
instructions except the call. But, on some platforms, if a value is returned as
a floating point, it may need to be removed from the stack (like x87). Thus, we
can't get rid of the bitcast even if there isn't a use of the value.
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also need to be checked for memory modifying instructions before we
can sink them. THis fixes the second half of PR2297.
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DemoteRegToStack doesn't work with MRVs yet, because it relies on the
ability to load/store things.
This fixes PR2285.
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we were checking for it in the wrong order. This caused a miscompilation because the
return slot optimization assumes that the call it is dealing with is NOT a memcpy.
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ComputeMaskedBits knows about cttz, ctlz, and ctpop. Teach
SelectionDAG's ComputeMaskedBits what InstCombine's knows
about SRem. And teach them both some things about high bits
in Mul, UDiv, URem, and Sub. This allows instcombine and
dagcombine to eliminate sign-extension operations in
several new cases.
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appropriate alignment. This fixes a miscompilation of 252.eon on
x86-64 (rdar://5891920).
Bill, please pull this into Tak.
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Fix said code to handle merging return instructions together correctly
when handling multiple return values.
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of -std-compile-opts and is now failing because other passes are generating
IR that looks different to input of loop rotate. Devang, please
introduce a testcase that only runs loop rotate.
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getelementptr-seteq.ll into:
define i1 @test(i64 %X, %S* %P) {
%C = icmp eq i64 %X, -1 ; <i1> [#uses=1]
ret i1 %C
}
instead of:
define i1 @test(i64 %X, %S* %P) {
%A.idx.mask = and i64 %X, 4611686018427387903 ; <i64> [#uses=1]
%C = icmp eq i64 %A.idx.mask, 4611686018427387903 ; <i1> [#uses=1]
ret i1 %C
}
And fixes the second half of PR2235. This speeds up the insertion sort
case by 45%, from 1.12s to 0.77s. In practice, this will significantly
speed up for loops structured like:
for (double *P = Base + N; P != Base; --P)
...
Which happens frequently for C++ iterators.
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from transforming loops and adding a separate loop pass for removing
loops with know trip counts. Until that happens, ADCE is miscompiling this code.
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in addition to integer expressions. Rewrite GetOrEnforceKnownAlignment
as a ComputeMaskedBits problem, moving all of its special alignment
knowledge to ComputeMaskedBits as low-zero-bits knowledge.
Also, teach ComputeMaskedBits a few basic things about Mul and PHI
instructions.
This improves ComputeMaskedBits-based simplifications in a few cases,
but more noticeably it significantly improves instcombine's alignment
detection for loads, stores, and memory intrinsics.
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This fires dozens of times across spec and multisource, but I don't know
if it actually speeds stuff up. Hopefully the testers will show something
nice :)
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simplify things like (X & 4) >> 1 == 2 --> (X & 4) == 4.
since it is obvious that the shift doesn't remove any bits.
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the type instead of the byte size. This was causing troublesome mis-compilations.
True to form, this took 2 days to find and is a one-line fix. :-P
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safer (when the passed pointer might be invalid). Thanks to Duncan and Chris for the idea behind this,
and extra thanks to Duncan for helping me work out the trap-safety.
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before trying to merge the block into its predecessors.
This allows two-entry-phi-return.ll to be simplified
into a single basic block.
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Secondly, we have to check whether the branch is actually pointing to the block
with the unwind in it. We could have gotten here because of the unwind_to alone.
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a union containing a vector and an array whose elements were smaller than
the vector elements. this means we need to compile the load of the
array elements into an extract element plus a truncate.
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not safe. This is fixed by more aggressively checking that the return slot is
not used elsewhere in the function.
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another sret function, it should pass its own sret parameter to the tail callee, allowing it to fill in the correct
return value. llvm-gcc does not emit this by default. Instead, it allocates space in the caller for the sret of
the tail call and then uses memcpy to copy the result into the caller's sret parameter. This optimization detects
and optimizes that case.
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was incorrectly simplifying "x == (gep x, 1, i)" into false, even
though i could be negative. As it turns out, all the code to
handle this already existed, we just need to disable the incorrect
optimization case and let the general case handle it.
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In practice this can only happen on code with already undefined behavior,
but this is still a good thing to handle correctly.
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way or the other. Rewriting the code itself prevents subsequent analysis
passes from making contradictory conclusions about the code that could
cause an infeasible path to be made feasible.
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promoted functions. This is important for varargs calls in
particular. Thanks to duncan for providing a great testcase.
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drop attributes on varargs call arguments. Also, it could generate
invalid IR if the transformed call already had the 'nest' attribute
somewhere (this can never happen for code coming from llvm-gcc,
but it's a theoretical possibility). Fix both problems.
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byval work. This miscompilation is due to the program indexing an array out
of range and us doing a transformation that broke this.
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a load/store of i64. The later prevents promotion/scalarrepl of the
source and dest in many cases.
This fixes the 300% performance regression of the byval stuff on
stepanov_v1p2.
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realize that ne & sgt was a signed comparison (it was only
looking at whether the left compare was signed).
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if this becomes a varargs call then deal correctly with any
parameter attributes on the newly vararg call arguments.
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inlining a function if we know that the function does not write
to *any* memory. This implements test/Transforms/Inline/byval2.ll
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get away with it, which exposes opportunities to eliminate the memory
objects entirely. For example, we now compile byval.ll to:
define internal void @f1(i32 %b.0, i64 %b.1) {
entry:
%tmp2 = add i32 %b.0, 1 ; <i32> [#uses=0]
ret void
}
define i32 @main() nounwind {
entry:
call void @f1( i32 1, i64 2 )
ret i32 0
}
This seems like it would trigger a lot for code that passes around small
structs (e.g. SDOperand's or _Complex)...
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direct calls bails out unless caller and callee have essentially
equivalent parameter attributes. This is illogical - the callee's
attributes should be of no relevance here. Rework the logic, which
incidentally fixes a crash when removed arguments have attributes.
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a direct call with cast parameters and cast return
value (if any), instcombine was prepared to cast any
non-void return value into any other, whether castable
or not. Add a new predicate for testing whether casting
is valid, and check it both for the return value and
(as a cleanup) for the parameters.
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could theoretically introduce a trap, but is also a performance issue.
This speeds up ptrdist/ks by 8%.
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return attributes on the floor. In the case of a call
to a varargs function where the varargs arguments are
being removed, any call attributes on those arguments
need to be dropped. I didn't do this because I plan to
make it illegal to have such attributes (see next patch).
With this change, compiling the gcc filter2 eh test at -O0
and then running opt -std-compile-opts on it results in
a correctly working program (compiling at -O1 or higher
results in the test failing due to a problem with how we
output eh info into the IR).
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