If this patch causes a performance regression for anyone, please let me know,
and it can be fixed in a different way with much more effort.
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returned by BinomialCoefficient and don't try to operate with them. This
replaces the previous fix for PR2857.
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- Recognize expressions like "x > -1 ? x : 0" as min/max and turn them
into expressions like "x < 0 ? 0 : x", which is easily recognizable
as a min/max operation.
- Refrain from folding expression like "y/2 < 1" to "y < 2" when the
comparison is being used as part of a min or max idiom, like
"y/2 < 1 ? 1 : y/2". In that case, the division has another use, so
folding doesn't eliminate it, and obfuscates the min/max, making it
harder to recognize as a min/max operation.
These benefit ScalarEvolution, CodeGen, and anything else that wants to
recognize integer min and max.
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its callers to emit a space character before calling it when a
space is needed.
This fixes several spurious whitespace issues in
ScalarEvolution's debug dumps. See the test changes for
examples.
This also fixes odd space-after-tab indentation in the output
for switch statements, and changes calls from being printed like
this:
call void @foo( i32 %x )
to this:
call void @foo(i32 %x)
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continue past the first conditional branch when looking for a
relevant test. This helps it avoid using MAX expressions in
loop trip counts in more cases.
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version uses a new algorithm for evaluating the binomial coefficients
which is significantly more efficient for AddRecs of more than 2 terms
(see the comments in the code for details on how the algorithm works).
It also fixes some bugs: it removes the arbitrary length restriction for
AddRecs, it fixes the silent generation of incorrect code for AddRecs
which require a wide calculation width, and it fixes an issue where we
were incorrectly truncating the iteration count too far when evaluating
an AddRec expression narrower than the induction variable.
There are still a few related issues I know of: I think there's
still an issue with the SCEVExpander expansion of AddRec in terms of
the width of the induction variable used. The hack to avoid generating
too-wide integers shouldn't be necessary; instead, the callers should be
considering the cost of the expansion before expanding it (in addition
to not expanding too-wide integers, we might not want to expand
expressions that are really expensive, especially when optimizing for
size; calculating an length-17 32-bit AddRec currently generates about 250
instructions of straight-line code on X86). Also, for long 32-bit
AddRecs on X86, CodeGen really sucks at scheduling the code. I'm planning on
filing follow-up PRs for these issues.
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time applying to the implicit comparison in smin expressions. The
correct way to transform an inequality into the opposite
inequality, either signed or unsigned, is with a not expression.
I looked through the SCEV code, and I don't think there are any more
occurrences of this issue.
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SGT exit condition. Essentially, the correct way to flip an inequality
in 2's complement is the not operator, not the negation operator.
That said, the difference only affects cases involving INT_MIN.
Also, enhance the pre-test search logic to be a bit smarter about
inequalities flipped with a not operator, so it can eliminate the smax
from the iteration count for simple loops.
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bail after 256-bits to avoid producing code that the backends can't handle.
Previously, we capped it at 64-bits, preferring to miscompile in those cases.
This change also reverts much of r52248 because the invariants the code was
expecting are now being met.
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with code that was expecting different bit widths for different values.
Make getTruncateOrZeroExtend a method on ScalarEvolution, and use it.
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several things that were neither in an anonymous namespace nor static
but not intended to be global.
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manually performing the comparison. This allows the special
case to work correctly even in the case where someone is
experimenting with a different comparison function :-).
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Parse reversed smax and umax as smin and umin and express them with negative
or binary-not SCEVs (which are really just subtract under the hood).
Parse 'xor %x, -1' as (-1 - %x).
Remove dead code (ConstantInt::get always returns a ConstantInt).
Don't use getIntegerSCEV(-1, Ty). The first value is an int, then it gets
passed into a uint64_t. Instead, create the -1 directly from
ConstantInt::getAllOnesValue().
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variable (with step 1) and m is its final value. Then, the correct trip
count is SMAX(m,n)-n. Previously, we used SMAX(0,m-n), but m-n may
overflow and can't in general be interpreted as signed.
Patch by Nick Lewycky.
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to the RHS. This simple change allows to compute loop iteration count
for loops with condition similar to the one in the testcase (which seems
to be quite common).
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arbitrary iteration.
The patch:
1) changes SCEVSDivExpr into SCEVUDivExpr,
2) replaces PartialFact() function with BinomialCoefficient(); the
computations (essentially, the division) in BinomialCoefficient() are
performed with the apprioprate bitwidth necessary to avoid overflow;
unsigned division is used instead of the signed one.
Computations in BinomialCoefficient() require support from the code
generator for APInts. Currently, we use a hack rounding up the
neccessary bitwidth to the nearest power of 2. The hack is easy to turn
off in future.
One remaining issue: we assume the divisor of the binomial coefficient
formula can be computed accurately using 16 bits. It means we can handle
AddRecs of length up to 9. In future, we should use APInts to evaluate
the divisor.
Thanks to Nicholas for cooperation!
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Reimplement the xform in Analysis/ConstantFolding.cpp where we can use
targetdata to validate that it is safe. While I'm in there, fix some const
correctness issues and generalize the interface to the "operand folder".
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is disabled in the sense that it will refuse to create one from a UDiv
instruction, until the code is better tested.
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Use APFloat in UpgradeParser and AsmParser.
Change all references to ConstantFP to use the
APFloat interface rather than double. Remove
the ConstantFP double interfaces.
Use APFloat functions for constant folding arithmetic
and comparisons.
(There are still way too many places APFloat is
just a wrapper around host float/double, but we're
getting there.)
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Always pass the constant as the second parameter to HowManyLessThans.
Remove obsolete "isSigned" parameter.
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deleteValueFromRecords and loosen the types to all it to accept
Value* instead of just Instruction*, since this is what
ScalarEvolution uses internally anyway. This allows more flexibility
for future uses.
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add operands after constant operands. The recent change to recognize
sign-extend expressions caused this to be exposed more often.
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This created an ambiguity for expandInTy to decide when to use
sign-extension or zero-extension, but it turns out that most of its callers
don't actually need a type conversion, now that LLVM types don't have
explicit signedness. Drop expandInTy in favor of plain expand, and change
the few places that actually need a type conversion to do it themselves.
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Due to darwin gcc bug, one version of darwin linker coalesces
static const int, which defauts PassID based pass identification.
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Fix a div-by-zero bug noticed by APInt. This fixes:
test/Transforms/IndVarsSimplify/exit_value_tests.llx
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First round of ConstantRange changes. This makes all CR constructors use
only APInt and not use ConstantInt. Clients are adjusted accordingly.
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This feature is needed in order to support shifts of more than 255 bits
on large integer types. This changes the syntax for llvm assembly to
make shl, ashr and lshr instructions look like a binary operator:
shl i32 %X, 1
instead of
shl i32 %X, i8 1
Additionally, this should help a few passes perform additional optimizations.
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This is the final patch for this PR. It implements some minor cleanup
in the use of IntegerType, to wit:
1. Type::getIntegerTypeMask -> IntegerType::getBitMask
2. Type::Int*Ty changed to IntegerType* from Type*
3. ConstantInt::getType() returns IntegerType* now, not Type*
This also fixes PR1120.
Patch by Sheng Zhou.
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rename Type::getIntegralTypeMask to Type::getIntegerTypeMask.
This makes naming much more consistent. For example, there are now no longer any
instances of IntegerType that are not considered isInteger! :)
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recommended that getBoolValue be replaced with getZExtValue and that
get(bool) be replaced by get(const Type*, uint64_t). This implements
those changes.
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Merge ConstantIntegral and ConstantBool into ConstantInt.
Remove ConstantIntegral and ConstantBool from LLVM.
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This patch replaces signed integer types with signless ones:
1. [US]Byte -> Int8
2. [U]Short -> Int16
3. [U]Int -> Int32
4. [U]Long -> Int64.
5. Removal of isSigned, isUnsigned, getSignedVersion, getUnsignedVersion
and other methods related to signedness. In a few places this warranted
identifying the signedness information from other sources.
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This patch removes the SetCC instructions and replaces them with the ICmp
and FCmp instructions. The SetCondInst instruction has been removed and
been replaced with ICmpInst and FCmpInst.
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Rename getZeroExtend and getSignExtend to getZExt and getSExt to match
the the casting mnemonics in the rest of LLVM.
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The long awaited CAST patch. This introduces 12 new instructions into LLVM
to replace the cast instruction. Corresponding changes throughout LLVM are
provided. This passes llvm-test, llvm/test, and SPEC CPUINT2000 with the
exception of 175.vpr which fails only on a slight floating point output
difference.
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Make necessary changes to support DIV -> [SUF]Div. This changes llvm to
have three division instructions: signed, unsigned, floating point. The
bytecode and assembler are bacwards compatible, however.
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This patch implements the first increment for the Signless Types feature.
All changes pertain to removing the ConstantSInt and ConstantUInt classes
in favor of just using ConstantInt.
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PR726 by performing consistent signed division, not consistent unsigned
division when evaluating scev's. Do not touch udivs.
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into the LLVMAnalysis library.
This allows LLVMTranform and LLVMTransformUtils to be archives and linked
with LLVMAnalysis.a, which provides any missing definitions.
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If we fold three constants together (c1+c2+c3), make sure to keep
LHSC updated, instead of reusing (in this case), the 1 instead of the
partial sum.
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infinite loops (using the new replaceSymbolicValuesWithConcrete method).
This patch reverts this patch:
http://mail.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20050131/023830.html
... which was an attempted fix for this problem. Unfortunately, that patch
caused test/Regression/Transforms/IndVarsSimplify/exit_value_tests.llx to fail
and slightly castrated the entire analysis. This patch fixes it right.
This patch is dedicated to jeffc, for making me deal with this. :)
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Make only one print method to avoid overloaded virtual warnings when \
compiled with -Woverloaded-virtual
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All SPEC CFP 95 programs now work, though the JIT isn't loading -lf2c right
so they aren't testing correctly.
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to go in. This patch allows us to compute the trip count of loops controlled
by values loaded from constant arrays. The cannonnical example of this is
strlen when passed a constant argument:
for (int i = 0; "constantstring"[i]; ++i) ;
return i;
In this case, it will compute that the loop executes 14 times, which means
that the exit value of i is 14. Because of this, the loop gets DCE'd and
we are happy. This also applies to anything that does similar things, e.g.
loops like this:
const float Array[] = { 0.1, 2.1, 3.2, 23.21 };
for (int i = 0; Array[i] < 20; ++i)
and is actually fairly general.
The problem with this is that it almost never triggers. The reason is that
we run indvars and the loop optimizer only at compile time, which is before
things like strlen and strcpy have been inlined into the program from libc.
Because of this, it almost never is used (it triggers twice in specint2k).
I'm committing it because it DOES work, may be useful in the future, and
doesn't slow us down at all. If/when we start running the loop optimizer
at link-time (-O4?) this will be very nice indeed :)
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Move include/Config and include/Support into include/llvm/Config,
include/llvm/ADT and include/llvm/Support. From here on out, all LLVM
public header files must be under include/llvm/.
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by address. This prevents the resultant SCEV objects from depending on
where in memory other scev objects happen to live.
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structure to being dynamically computed on demand. This makes updating
loop information MUCH easier.
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operations. This allows us to compile this testcase:
int main() {
int h = 1;
do h = 3 * h + 1; while (h <= 256);
printf("%d\n", h);
return 0;
}
into this:
int %main() {
entry:
call void %__main( )
%tmp.6 = call int (sbyte*, ...)* %printf( sbyte* getelementptr ([4 x sbyte]* %.str_1, long 0, long 0), int 364 ) ; <int> [#uses=0]
ret int 0
}
This testcase was taken directly from 256.bzip2, believe it or not.
This code is not as general as I would like. Next up is to refactor it
a bit to handle more cases.
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even if the loop is using expressions that we can't compute as a closed-form.
This allows us to calculate that this function always returns 55:
int test() {
double X;
int Count = 0;
for (X = 100; X > 1; X = sqrt(X), ++Count)
/*empty*/;
return Count;
}
And allows us to compute trip counts for loops like:
int h = 1;
do h = 3 * h + 1; while (h <= 256);
(which occurs in bzip2), and for this function, which occurs after inlining
and other optimizations:
int popcount()
{
int x = 666;
int result = 0;
while (x != 0) {
result = result + (x & 0x1);
x = x >> 1;
}
return result;
}
We still cannot compute the exit values of result or h in the two loops above,
which means we cannot delete the loop, but we are getting closer. Being able to
compute a constant trip count for these two loops will allow us to unroll them
completely though.
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at the bottom of the loop instead of the top. This reduces the number of
overlapping live ranges a lot, for example, eliminating a spill in an important
loop in 183.equake with linear scan.
I still need to make the exit comparison of the loop use the post-incremented
version of this variable, but this is an easy first step.
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