stored rather than the pointer type.
This change is analogous to r220138 which changed the canonicalization
for loads. The rationale is the same: memory does not have a type,
operations (and thus the values they produce) have a type. We should
match that type as closely as possible rather than reading some form of
semantics into the pointer type.
With this change, loads and stores should no longer be made with
nonsensical types for the values that tehy load and store. This is
particularly important when trying to match specific loaded and stored
types in the process of doing other instcombines, which is what led me
down this twisty maze of miscanonicalization.
I've put quite some effort into looking through IR to find places where
LLVM's optimizer was being unreasonably conservative in the face of
mismatched load and store types, however it is possible (let's say,
likely!) I have missed some. If you see regressions here, or from
r220138, the likely cause is some part of LLVM failing to cope with load
and store types differing. Test cases appreciated, it is important that
we root all of these out of LLVM.
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An icmp may have pointer arguments, it isn't limited to integers or
vectors of integers.
This fixes PR21388.
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consider:
mul i32 nsw %x, -2147483648
this instruction will not result in poison if %x is 1
however, if we transform this into:
shl i32 nsw %x, 31
then we will be generating poison because we just shifted into the sign
bit.
This fixes PR21242.
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The LLVM Lang Ref states for signed/unsigned int to float conversions:
"If the value cannot fit in the floating point value, the results are undefined."
And for FP to signed/unsigned int:
"If the value cannot fit in ty2, the results are undefined."
This matches the C definitions.
The existing behavior pins to infinity or a max int value, but that may just
lead to more confusion as seen in:
http://llvm.org/bugs/show_bug.cgi?id=21130
Returning undef will hopefully lead to a less silent failure.
Differential Revision: http://reviews.llvm.org/D5603
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Consider:
%add = add nuw i32 %a, -16777216
%and = and i32 %add, 255
Regardless of whether or not we demand the sign bit of %add, we cannot
replace -16777216 with 2130706432 without also removing 'nuw' from the
instruction.
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Consider:
%add = add nsw i32 %a, -16777216
%and = and i32 %add, 255
Regardless of whether or not we demand the sign bit of %add, we cannot
replace -16777216 with 2130706432 without also removing 'nsw' from the
instruction.
This fixes PR20377.
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The code was actually correct. Sorry for the confusion. I have expanded the
comment saying why the analysis is valid to avoid me misunderstaning it
again in the future.
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This reverts commit r210029.
It was not correctly handling cases where LHS and RHS had multiple but different
sign bits.
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This update was done with the following bash script:
find test/Transforms -name "*.ll" | \
while read NAME; do
echo "$NAME"
if ! grep -q "^; *RUN: *llc" $NAME; then
TEMP=`mktemp -t temp`
cp $NAME $TEMP
sed -n "s/^define [^@]*@\([A-Za-z0-9_]*\)(.*$/\1/p" < $NAME | \
while read FUNC; do
sed -i '' "s/;\(.*\)\([A-Za-z0-9_]*\):\( *\)@$FUNC\([( ]*\)\$/;\1\2-LABEL:\3@$FUNC(/g" $TEMP
done
mv $TEMP $NAME
fi
done
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The shift amount may be larger than the type leading to undefined behavior.
Limit the transform to constant shift amounts. While there update the bits to
clear in the result which may enable additional optimizations.
PR15959.
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%V = mul i64 %N, 4
%t = getelementptr i8* bitcast (i32* %arr to i8*), i32 %V
into
%t1 = getelementptr i32* %arr, i32 %N
%t = bitcast i32* %t1 to i8*
incorporating the multiplication into the getelementptr.
This happens all the time in dragonegg, for example for
int foo(int *A, int N) {
return A[N];
}
because gcc turns this into byte pointer arithmetic before it hits the plugin:
D.1590_2 = (long unsigned int) N_1(D);
D.1591_3 = D.1590_2 * 4;
D.1592_5 = A_4(D) + D.1591_3;
D.1589_6 = *D.1592_5;
return D.1589_6;
The D.1592_5 line is a POINTER_PLUS_EXPR, which is turned into a getelementptr
on a bitcast of A_4 to i8*, so this becomes exactly the kind of IR that the
transform fires on.
An analogous transform (with no testcases!) already existed for bitcasts of
arrays, so I rewrote it to share code with this one.
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Original commit message:
Defer some shl transforms to DAGCombine.
The shl instruction is used to represent multiplication by a constant
power of two as well as bitwise left shifts. Some InstCombine
transformations would turn an shl instruction into a bit mask operation,
making it difficult for later analysis passes to recognize the
constsnt multiplication.
Disable those shl transformations, deferring them to DAGCombine time.
An 'shl X, C' instruction is now treated mostly the same was as 'mul X, C'.
These transformations are deferred:
(X >>? C) << C --> X & (-1 << C) (When X >> C has multiple uses)
(X >>? C1) << C2 --> X << (C2-C1) & (-1 << C2) (When C2 > C1)
(X >>? C1) << C2 --> X >>? (C1-C2) & (-1 << C2) (When C1 > C2)
The corresponding exact transformations are preserved, just like
div-exact + mul:
(X >>?,exact C) << C --> X
(X >>?,exact C1) << C2 --> X << (C2-C1)
(X >>?,exact C1) << C2 --> X >>?,exact (C1-C2)
The disabled transformations could also prevent the instruction selector
from recognizing rotate patterns in hash functions and cryptographic
primitives. I have a test case for that, but it is too fragile.
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While the patch was perfect and defect free, it exposed a really nasty
bug in X86 SelectionDAG that caused an llc crash when compiling lencod.
I'll put the patch back in after fixing the SelectionDAG problem.
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The shl instruction is used to represent multiplication by a constant
power of two as well as bitwise left shifts. Some InstCombine
transformations would turn an shl instruction into a bit mask operation,
making it difficult for later analysis passes to recognize the
constsnt multiplication.
Disable those shl transformations, deferring them to DAGCombine time.
An 'shl X, C' instruction is now treated mostly the same was as 'mul X, C'.
These transformations are deferred:
(X >>? C) << C --> X & (-1 << C) (When X >> C has multiple uses)
(X >>? C1) << C2 --> X << (C2-C1) & (-1 << C2) (When C2 > C1)
(X >>? C1) << C2 --> X >>? (C1-C2) & (-1 << C2) (When C1 > C2)
The corresponding exact transformations are preserved, just like
div-exact + mul:
(X >>?,exact C) << C --> X
(X >>?,exact C1) << C2 --> X << (C2-C1)
(X >>?,exact C1) << C2 --> X >>?,exact (C1-C2)
The disabled transformations could also prevent the instruction selector
from recognizing rotate patterns in hash functions and cryptographic
primitives. I have a test case for that, but it is too fragile.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155136 91177308-0d34-0410-b5e6-96231b3b80d8
Optimize chained bitcasts of the form A->B->A.
Undo r138722 and change isEliminableCastPair to allow this case.
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exact/nsw/nuw shifts and have instcombine infer them when it can prove
that the relevant properties are true for a given shift without them.
Also, a variety of refactoring to use the new patternmatch logic thrown
in for good luck. I believe that this takes care of a bunch of related
code quality issues attached to PR8862.
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to expose greater opportunities for store narrowing in codegen. This patch fixes a potential
infinite loop in instcombine caused by one of the introduced transforms being overly aggressive.
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This can result in increased opportunities for store narrowing in code generation. Update a number of
tests for this change. This fixes <rdar://problem/8285027>.
Additionally, because this inverts the order of ors and ands, some patterns for optimizing or-of-and-of-or
no longer fire in instances where they did originally. Add a simple transform which recaptures most of these
opportunities: if we have an or-of-constant-or and have failed to fold away the inner or, commute the order
of the two ors, to give the non-constant or a chance for simplification instead.
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with a vector input and output into a shuffle vector. This sort of
sequence happens when the input code stores with one type and reloads
with another type and then SROA promotes to i96 integers, which make
everyone sad.
This fixes rdar://7896024
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BitsToClear case. This allows it to promote expressions which have an
and/or/xor after the lshr, promoting cases like test2 (from PR4216)
and test3 (random extample extracted from a spec benchmark).
clang now compiles the code in PR4216 into:
_test_bitfield: ## @test_bitfield
movl %edi, %eax
orl $194, %eax
movl $4294902010, %ecx
andq %rax, %rcx
orl $32768, %edi
andq $39936, %rdi
movq %rdi, %rax
orq %rcx, %rax
ret
instead of:
_test_bitfield: ## @test_bitfield
movl %edi, %eax
orl $194, %eax
movl $4294902010, %ecx
andq %rax, %rcx
shrl $8, %edi
orl $128, %edi
shlq $8, %rdi
andq $39936, %rdi
movq %rdi, %rax
orq %rcx, %rax
ret
which is still not great, but is progress.
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new BitsToClear result which allows us to start promoting
expressions that end with a lshr-by-constant. This is
conservatively correct and better than what we had before
(see testcases) but still needs to be extended further.
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the zext dest type. This allows us to handle test52/53 in cast.ll,
and allows llvm-gcc to generate much better code for PR4216 in -m64
mode:
_test_bitfield: ## @test_bitfield
orl $32962, %edi
movl %edi, %eax
andl $-25350, %eax
ret
This also fixes a bug handling vector extends, ensuring that the
mask produced is a vector constant, not an integer constant.
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elimination of a sign extend to be a win, which simplifies
the client of CanEvaluateSExtd, and allows us to eliminate
more casts (examples taken from real code).
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1) don't try to optimize a sext or zext that is only used by a trunc, let
the trunc get optimized first. This avoids some pointless effort in
some common cases since instcombine scans down a block in the first pass.
2) Change the cost model for zext elimination to consider an 'and' cheaper
than a zext. This allows us to do it more aggressively, and for the next
patch to simplify the code quite a bit.
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that feeds into a zext, similar to the patch I did yesterday for sext.
There is a lot of room for extension beyond this patch.
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Previously, instcombine would only promote an expression tree to
the larger type if doing so eliminated two casts. This is because
a need to manually do the sign extend after the promoted expression
tree with two shifts. Now, we keep track of whether the result of
the computation is going to be properly sign extended already. If
so, we can unconditionally promote the expression, which allows us
to zap more sext's.
This implements rdar://6598839 (aka gcc pr38751)
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ConstantExpr, not just the top-level operator. This allows it to
fold many more constants.
Also, make GlobalOpt call ConstantFoldConstantExpression on
GlobalVariable initializers.
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Update testcases that rely on malloc insts being present.
Also prematurely remove MallocInst handling from IndMemRemoval and RaiseAllocations to help pass tests in this incremental step.
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