When trying to collapse sequences of insertelement/extractelement
instructions into single shuffle instructions, there is one specific
case where the Instruction Combiner wrongly updates the resulting
Mask of shuffle indexes.
The problem is in function CollectShuffleElments.
If we have a sequence of insert/extract element instructions
like the one below:
%tmp1 = extractelement <4 x float> %LHS, i32 0
%tmp2 = insertelement <4 x float> %RHS, float %tmp1, i32 1
%tmp3 = extractelement <4 x float> %RHS, i32 2
%tmp4 = insertelement <4 x float> %tmp2, float %tmp3, i32 3
Where:
. %RHS will have a mask of [4,5,6,7]
. %LHS will have a mask of [0,1,2,3]
The Mask of shuffle indexes is wrongly computed to [4,1,6,7]
instead of [4,0,6,7].
When analyzing %tmp2 in order to compute the Mask for the
resulting shuffle instruction, the algorithm forgets to update
the mask index at position 1 with the index associated to the
element extracted from %LHS by instruction %tmp1.
Patch by Andrea DiBiagio!
llvm-svn: 179291
The OptimizeIntToFloatBitCast converts shift-truncate sequences
into extractelement operations. The computation of the element
index to be used in the resulting operation is currently only
correct for little-endian targets.
This commit fixes the element index computation to be correct
for big-endian targets as well. If the target byte order is
unknown, the optimization cannot be performed at all.
llvm-svn: 178031
The problem is that the code mistakenly took for granted that following constructor
is able to create an APFloat from a *SIGNED* integer:
APFloat::APFloat(const fltSemantics &ourSemantics, integerPart value)
rdar://13486998
llvm-svn: 177906
This simplification happens at 2 places :
- using the nsw attribute when the shl / mul is used by a sign test
- when the shl / mul is compared for (in)equality to zero
llvm-svn: 177856
The original code used i32, and i64 if legal. This introduced unneeded
casts when they aren't legal, or when the index variable i has another
type. In order of preference: try to use i's type; use the smallest
fitting legal type (using an added DataLayout method); default to i32.
A testcase checks that this works when the index gep operand is i16.
Patch by : Ahmed Bougacha <ahmed.bougacha@gmail.com>
Reviewed by : Duncan
llvm-svn: 177712
Rules include:
1)1 x*y +/- x*z => x*(y +/- z)
(the order of operands dosen't matter)
2) y/x +/- z/x => (y +/- z)/x
The transformation is disabled if the new add/sub expr "y +/- z" is a
denormal/naz/inifinity.
rdar://12911472
llvm-svn: 177088
When considering folding a bitcast of an alloca into the alloca itself,
make sure we don't shrink the amount of memory being allocated, or
things rapidly go sideways.
rdar://13324424
llvm-svn: 176547
The instcombine recognized pattern looks like:
a = b * c
d = a +/- Cst
or
a = b * c
d = Cst +/- a
When creating the new operands for fadd or fsub instruction following the related fmul, the first operand was created with the second original operand (M0 was created with C1) and the second with the first (M1 with Opnd0).
The fix consists in creating the new operands with the appropriate original operand, i.e., M0 with Opnd0 and M1 with C1.
llvm-svn: 176300
(or (bool?A:B),(bool?C:D)) --> (bool?(or A,C):(or B,D))
By the time the OR is visited, both the SELECTs have been visited and not
optimized and the OR itself hasn't been transformed so we do this transform in
the hopes that the new ORs will be optimized.
The transform is explicitly disabled for vector-selects until "codegen matures
to handle them better".
Patch by Muhammad Tauqir!
llvm-svn: 175380
It enables to work with a smaller constant, which is target friendly for those which can compare to immediates.
It also avoids inserting a shift in favor of a trunc, which can be free on some targets.
This used to work until LLVM-3.1, but regressed with the 3.2 release.
llvm-svn: 175270
In the future, AttributeWithIndex won't be used anymore. Besides, it exposes the
internals of the AttributeSet to outside users, which isn't goodness.
llvm-svn: 173602
The 'getSlot' function and its ilk allow introspection into the AttributeSet
class. However, that class should be opaque. Allow access through accessor
methods instead.
llvm-svn: 173522
Collections of attributes are handled via the AttributeSet class now. This
finally frees us up to make significant changes to how attributes are structured.
llvm-svn: 173228
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.
llvm-svn: 173094
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.
llvm-svn: 172844
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.
llvm-svn: 172551
---------------------------------------------------------------------------
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)
llvm-svn: 172488