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/**
* Provides a language-independent implementation of static single assignment
* (SSA) form.
*/
overlay[local?]
module;
private import codeql.controlflow.BasicBlock as BB
private import codeql.util.Location
private import codeql.util.Unit
signature class BasicBlockSig;
/** Provides the input specification of the SSA implementation. */
signature module InputSig<LocationSig Location, BasicBlockSig BasicBlock> {
/** A variable that can be SSA converted. */
class SourceVariable {
/** Gets a textual representation of this variable. */
string toString();
/** Gets the location of this variable. */
Location getLocation();
}
/**
* Holds if the `i`th node of basic block `bb` is a (potential) write to source
* variable `v`. The Boolean `certain` indicates whether the write is certain.
*
* Examples of uncertain writes are `ref` arguments in C#, where it is the callee
* that may or may not update the argument.
*/
predicate variableWrite(BasicBlock bb, int i, SourceVariable v, boolean certain);
/**
* Holds if the `i`th node of basic block `bb` reads source variable `v`. The
* Boolean `certain` indicates whether the read is certain.
*
* Examples of uncertain reads are pseudo-reads inserted at the end of a C# method
* with a `ref` or `out` parameter, where it is the caller that may or may not read
* the argument.
*/
predicate variableRead(BasicBlock bb, int i, SourceVariable v, boolean certain);
}
/**
* Provides an SSA implementation.
*
* The SSA construction is pruned based on liveness. That is, SSA definitions are only
* constructed for `Input::variableWrite`s when it is possible to reach an
* `Input::variableRead`, without going through a certain write (the same goes for `phi`
* nodes). Whenever a variable is both read and written at the same index in some basic
* block, the read is assumed to happen before the write.
*
* The result of invoking this parameterized module is not meant to be exposed directly;
* instead, one should define a language-specific layer on top, and make sure to cache
* all exposed predicates marked with
*
* ```
* NB: If this predicate is exposed, it should be cached.
* ```
*/
module Make<
LocationSig Location, BB::CfgSig<Location> Cfg, InputSig<Location, Cfg::BasicBlock> Input>
{
private import Cfg
private import Input
private BasicBlock getABasicBlockPredecessor(BasicBlock bb) { result.getASuccessor() = bb }
/**
* A classification of variable references into reads and
* (certain or uncertain) writes / definitions.
*/
private newtype TRefKind =
Read() or
Write(boolean certain) { certain in [false, true] } or
Def()
private class RefKind extends TRefKind {
string toString() {
this = Read() and result = "read"
or
exists(boolean certain | this = Write(certain) and result = "write (" + certain + ")")
or
this = Def() and result = "def"
}
int getOrder() {
this = Read() and
result = 0
or
this = Write(_) and
result = 1
or
this = Def() and
result = 1
}
}
/**
* Holds if the `i`th node of basic block `bb` is a reference to `v` of kind `k`.
*/
private signature predicate refSig(BasicBlock bb, int i, SourceVariable v, RefKind k);
private module RankRefs<refSig/4 ref> {
private newtype OrderedRefIndex =
MkOrderedRefIndex(int i, int tag) {
exists(RefKind rk | ref(_, i, _, rk) | tag = rk.getOrder())
}
private OrderedRefIndex refOrd(BasicBlock bb, int i, SourceVariable v, RefKind k, int ord) {
ref(bb, i, v, k) and
result = MkOrderedRefIndex(i, ord) and
ord = k.getOrder()
}
/**
* Gets the (1-based) rank of the reference to `v` at the `i`th node of
* basic block `bb`, which has the given reference kind `k`.
*
* Reads are considered before writes when they happen at the same index.
*/
int refRank(BasicBlock bb, int i, SourceVariable v, RefKind k) {
refOrd(bb, i, v, k, _) =
rank[result](int j, int ord, OrderedRefIndex res |
res = refOrd(bb, j, v, _, ord)
|
res order by j, ord
)
}
int maxRefRank(BasicBlock bb, SourceVariable v) {
result = refRank(bb, _, v, _) and
not result + 1 = refRank(bb, _, v, _)
}
}
/**
* Liveness analysis (based on source variables) to restrict the size of the
* SSA representation.
*/
private module Liveness {
/**
* Holds if the `i`th node of basic block `bb` is a reference to `v` of kind `k`.
*/
predicate varRef(BasicBlock bb, int i, SourceVariable v, RefKind k) {
variableRead(bb, i, v, _) and k = Read()
or
exists(boolean certain | variableWrite(bb, i, v, certain) | k = Write(certain))
}
private import RankRefs<varRef/4>
/**
* Gets the (1-based) rank of the first reference to `v` inside basic block `bb`
* that is either a read or a certain write.
*
* Note that uncertain writes have no impact on liveness: a variable is
* live before an uncertain write if and only if it is live after.
* The reference identified here therefore determines liveness at the
* beginning of `bb`: if it is a read then the variable is live and if it
* is a write then it is not. For basic blocks without reads or certain
* writes, liveness at the beginning of the block is equivalent to liveness
* at the end of the block.
*/
private int firstReadOrCertainWrite(BasicBlock bb, SourceVariable v) {
result =
min(int r, RefKind k |
r = refRank(bb, _, v, k) and
k != Write(false)
|
r
)
}
/**
* Holds if source variable `v` is live at the beginning of basic block `bb`.
*/
predicate liveAtEntry(BasicBlock bb, SourceVariable v) {
// The first read or certain write to `v` inside `bb` is a read
refRank(bb, _, v, Read()) = firstReadOrCertainWrite(bb, v)
or
// There is no certain write to `v` inside `bb`, but `v` is live at entry
// to a successor basic block of `bb`
not exists(firstReadOrCertainWrite(bb, v)) and
liveAtExit(bb, v)
}
/**
* Holds if source variable `v` is live at the end of basic block `bb`.
*/
predicate liveAtExit(BasicBlock bb, SourceVariable v) { liveAtEntry(bb.getASuccessor(), v) }
/**
* Holds if variable `v` is live in basic block `bb` at rank `rnk`.
*/
private predicate liveAtRank(BasicBlock bb, SourceVariable v, int rnk) {
exists(RefKind kind | rnk = refRank(bb, _, v, kind) |
rnk = maxRefRank(bb, v) and
liveAtExit(bb, v)
or
kind = Read()
or
exists(RefKind nextKind |
liveAtRank(bb, v, rnk + 1) and
rnk + 1 = refRank(bb, _, v, nextKind) and
nextKind != Write(true)
)
)
}
/**
* Holds if variable `v` is live after the (certain or uncertain) write at
* index `i` inside basic block `bb`.
*/
predicate liveAfterWrite(BasicBlock bb, int i, SourceVariable v) {
exists(int rnk | rnk = refRank(bb, i, v, Write(_)) | liveAtRank(bb, v, rnk))
}
}
private import Liveness
/**
* Holds if `bb` is in the dominance frontier of a block containing a
* definition of `v`.
*/
pragma[noinline]
private predicate inDefDominanceFrontier(BasicBlock bb, SourceVariable v) {
exists(BasicBlock defbb, Definition def |
def.definesAt(v, defbb, _) and
defbb.inDominanceFrontier(bb)
)
}
/**
* Holds if `bb` is in the dominance frontier of a block containing a
* read of `v`.
*/
pragma[nomagic]
private predicate inReadDominanceFrontier(BasicBlock bb, SourceVariable v) {
exists(BasicBlock readbb | readbb.inDominanceFrontier(bb) |
ssaDefReachesRead(v, _, readbb, _) and
variableRead(readbb, _, v, true) and
not variableWrite(readbb, _, v, _)
or
synthPhiRead(readbb, v) and
not varRef(readbb, _, v, _)
)
}
/**
* Holds if we should synthesize a pseudo-read of `v` at the beginning of `bb`.
*
* These reads are named phi-reads, since they are constructed in the same
* way as ordinary phi nodes except all reads are treated as potential
* "definitions". This ensures that use-use flow has the same dominance
* properties as def-use flow.
*/
private predicate synthPhiRead(BasicBlock bb, SourceVariable v) {
inReadDominanceFrontier(bb, v) and
liveAtEntry(bb, v) and
// no need to create a phi-read if there is already a normal phi
not any(PhiNode def).definesAt(v, bb, _)
}
cached
private newtype TDefinitionExt =
TWriteDef(SourceVariable v, BasicBlock bb, int i) {
variableWrite(bb, i, v, _) and
liveAfterWrite(bb, i, v)
} or
TPhiNode(SourceVariable v, BasicBlock bb) {
inDefDominanceFrontier(bb, v) and
liveAtEntry(bb, v)
} or
TPhiReadNode(SourceVariable v, BasicBlock bb) { synthPhiRead(bb, v) }
private class TDefinition = TWriteDef or TPhiNode;
private module SsaDefReachesNew {
/**
* Holds if the `i`th node of basic block `bb` is a reference to `v`,
* either a read (when `k` is `Read()`) or an SSA definition (when
* `k` is `Def()`).
*
* Unlike `Liveness::varRef`, this includes `phi` nodes and pseudo-reads
* associated with uncertain writes.
*/
pragma[nomagic]
predicate ssaRef(BasicBlock bb, int i, SourceVariable v, RefKind k) {
variableRead(bb, i, v, _) and
k = Read()
or
variableWrite(bb, i, v, false) and
k = Read()
or
any(Definition def).definesAt(v, bb, i) and
k = Def()
}
private import RankRefs<ssaRef/4>
/**
* Holds if the SSA definition `def` reaches rank index `rnk` in its own
* basic block `bb`.
*/
predicate ssaDefReachesRank(BasicBlock bb, Definition def, int rnk, SourceVariable v) {
exists(int i |
rnk = refRank(bb, i, v, Def()) and
def.definesAt(v, bb, i)
)
or
ssaDefReachesRank(bb, def, rnk - 1, v) and
rnk = refRank(bb, _, v, Read())
}
/**
* Holds if `v` is live at the end of basic block `bb` with the same value as at
* the end of the immediate dominator, `idom`, of `bb`.
*/
pragma[nomagic]
private predicate liveThrough(BasicBlock idom, BasicBlock bb, SourceVariable v) {
idom = bb.getImmediateDominator() and
liveAtExit(bb, v) and
not any(Definition def).definesAt(v, bb, _)
}
/**
* Holds if the SSA definition of `v` at `def` reaches the end of basic
* block `bb`, at which point it is still live, without crossing another
* SSA definition of `v`.
*/
pragma[nomagic]
predicate ssaDefReachesEndOfBlock(BasicBlock bb, Definition def, SourceVariable v) {
exists(int last |
last = maxRefRank(pragma[only_bind_into](bb), pragma[only_bind_into](v)) and
ssaDefReachesRank(bb, def, last, v) and
liveAtExit(bb, v)
)
or
exists(BasicBlock idom |
// The construction of SSA form ensures that each read of a variable is
// dominated by its definition. An SSA definition therefore reaches a
// control flow node if it is the _closest_ SSA definition that dominates
// the node. If two definitions dominate a node then one must dominate the
// other, so therefore the definition of _closest_ is given by the dominator
// tree. Thus, reaching definitions can be calculated in terms of dominance.
ssaDefReachesEndOfBlock(idom, def, v) and
liveThrough(idom, bb, v)
)
}
/**
* Holds if the SSA definition of `v` at `def` reaches index `i` in its own
* basic block `bb`, without crossing another SSA definition of `v`.
*/
predicate ssaDefReachesReadWithinBlock(SourceVariable v, Definition def, BasicBlock bb, int i) {
exists(int rnk |
ssaDefReachesRank(bb, def, rnk, v) and
rnk = refRank(bb, i, v, Read())
)
}
/**
* Holds if the SSA definition of `v` at `def` reaches a read at index `i` in
* basic block `bb`, without crossing another SSA definition of `v`.
*/
pragma[nomagic]
predicate ssaDefReachesRead(SourceVariable v, Definition def, BasicBlock bb, int i) {
ssaDefReachesReadWithinBlock(v, def, bb, i)
or
ssaRef(bb, i, v, Read()) and
ssaDefReachesEndOfBlock(bb.getImmediateDominator(), def, v) and
not ssaDefReachesReadWithinBlock(v, _, bb, i)
}
predicate uncertainWriteDefinitionInput(UncertainWriteDefinition def, Definition inp) {
exists(SourceVariable v, BasicBlock bb, int i |
def.definesAt(v, bb, i) and
ssaDefReachesRead(v, inp, bb, i)
)
}
}
private module AdjacentSsaRefs {
/**
* Holds if the `i`th node of basic block `bb` is a reference to `v`,
* either a read (when `k` is `Read()`) or an SSA definition (when
* `k` is `Def()`).
*
* Unlike `Liveness::varRef`, this includes phi nodes, phi reads, and
* pseudo-reads associated with uncertain writes, but excludes uncertain
* reads.
*/
pragma[nomagic]
predicate ssaRef(BasicBlock bb, int i, SourceVariable v, RefKind k) {
variableRead(bb, i, v, true) and
k = Read()
or
variableWrite(bb, i, v, false) and
k = Read()
or
any(Definition def).definesAt(v, bb, i) and
k = Def()
or
synthPhiRead(bb, v) and i = -1 and k = Def()
}
private import RankRefs<ssaRef/4>
/**
* Holds if `v` is live at the end of basic block `bb`, which contains no
* reference to `v`, and `idom` is the immediate dominator of `bb`.
*/
pragma[nomagic]
private predicate liveThrough(BasicBlock idom, BasicBlock bb, SourceVariable v) {
idom = bb.getImmediateDominator() and
liveAtExit(bb, v) and
not ssaRef(bb, _, v, _)
}
pragma[nomagic]
private predicate refReachesEndOfBlock(BasicBlock bbRef, int i, BasicBlock bb, SourceVariable v) {
maxRefRank(bb, v) = refRank(bb, i, v, _) and
liveAtExit(bb, v) and
bbRef = bb
or
exists(BasicBlock idom |
refReachesEndOfBlock(bbRef, i, idom, v) and
liveThrough(idom, bb, v)
)
}
/**
* Holds if `v` has adjacent references at index `i1` in basic block `bb1`
* and index `i2` in basic block `bb2`, that is, there is a path between
* the first reference to the second without any other reference to `v` in
* between. References include certain reads, SSA definitions, and
* pseudo-reads in the form of phi-reads. The first reference can be any of
* these kinds while the second is restricted to certain reads and
* uncertain writes.
*
* Note that the placement of phi-reads ensures that the first reference is
* uniquely determined by the second and that the first reference dominates
* the second.
*/
predicate adjacentRefRead(BasicBlock bb1, int i1, BasicBlock bb2, int i2, SourceVariable v) {
bb1 = bb2 and
refRank(bb1, i1, v, _) + 1 = refRank(bb2, i2, v, Read())
or
refReachesEndOfBlock(bb1, i1, bb2.getImmediateDominator(), v) and
1 = refRank(bb2, i2, v, Read())
}
/**
* Holds if the phi node or phi-read for `v` in basic block `bbPhi` takes
* input from basic block `input`, and that the reference to `v` at index
* `i` in basic block `bb` reaches the end of `input` without going through
* any other reference to `v`.
*/
predicate adjacentRefPhi(
BasicBlock bb, int i, BasicBlock input, BasicBlock bbPhi, SourceVariable v
) {
refReachesEndOfBlock(bb, i, input, v) and
input = getABasicBlockPredecessor(bbPhi) and
1 = refRank(bbPhi, -1, v, _)
}
private predicate adjacentRefs(BasicBlock bb1, int i1, BasicBlock bb2, int i2, SourceVariable v) {
adjacentRefRead(bb1, i1, bb2, i2, v)
or
adjacentRefPhi(bb1, i1, _, bb2, v) and i2 = -1
}
/**
* Holds if the reference to `v` at index `i1` in basic block `bb1` reaches
* the certain read at index `i2` in basic block `bb2` without going
* through any other certain read. The boolean `samevar` indicates whether
* the two references are to the same SSA variable.
*
* Note that since this relation skips over phi nodes and phi reads, it may
* be quadratic in the number of variable references for certain access
* patterns.
*/
predicate firstUseAfterRef(
BasicBlock bb1, int i1, BasicBlock bb2, int i2, SourceVariable v, boolean samevar
) {
adjacentRefs(bb1, i1, bb2, i2, v) and
variableRead(bb2, i2, v, _) and
samevar = true
or
exists(BasicBlock bb0, int i0, boolean samevar0 |
firstUseAfterRef(bb0, i0, bb2, i2, v, samevar0) and
adjacentRefs(bb1, i1, bb0, i0, v) and
not variableWrite(bb0, i0, v, true) and
if any(Definition def).definesAt(v, bb0, i0)
then samevar = false
else (
samevar = samevar0 and synthPhiRead(bb0, v) and i0 = -1
)
)
}
}
/**
* Holds if `def` reaches the certain read at index `i` in basic block `bb`
* without going through any other certain read. The boolean `samevar`
* indicates whether the read is a use of `def` or whether some number of phi
* nodes and/or uncertain reads occur between `def` and the read.
*
* Note that since this relation skips over phi nodes and phi reads, it may
* be quadratic in the number of variable references for certain access
* patterns.
*/
predicate firstUse(Definition def, BasicBlock bb, int i, boolean samevar) {
exists(BasicBlock bb1, int i1, SourceVariable v |
def.definesAt(v, bb1, i1) and
AdjacentSsaRefs::firstUseAfterRef(bb1, i1, bb, i, v, samevar)
)
}
/**
* Holds if the certain read at index `i1` in basic block `bb1` reaches the
* certain read at index `i2` in basic block `bb2` without going through any
* other certain read. The boolean `samevar` indicates whether the two reads
* are of the same SSA variable.
*
* Note that since this relation skips over phi nodes and phi reads, it may
* be quadratic in the number of variable references for certain access
* patterns.
*/
predicate adjacentUseUse(
BasicBlock bb1, int i1, BasicBlock bb2, int i2, SourceVariable v, boolean samevar
) {
exists(boolean samevar0 |
variableRead(bb1, i1, v, true) and
not variableWrite(bb1, i1, v, true) and
AdjacentSsaRefs::firstUseAfterRef(bb1, i1, bb2, i2, v, samevar0) and
if any(Definition def).definesAt(v, bb1, i1) then samevar = false else samevar = samevar0
)
}
private module SsaDefReaches {
deprecated newtype TSsaRefKind =
SsaActualRead() or
SsaPhiRead() or
SsaDef()
deprecated class SsaRead = SsaActualRead or SsaPhiRead;
deprecated class SsaDefExt = SsaDef or SsaPhiRead;
deprecated SsaDefExt ssaDefExt() { any() }
/**
* A classification of SSA variable references into reads and definitions.
*/
deprecated class SsaRefKind extends TSsaRefKind {
string toString() {
this = SsaActualRead() and
result = "SsaActualRead"
or
this = SsaPhiRead() and
result = "SsaPhiRead"
or
this = SsaDef() and
result = "SsaDef"
}
int getOrder() {
this instanceof SsaRead and
result = 0
or
this = SsaDef() and
result = 1
}
}
/**
* Holds if the `i`th node of basic block `bb` is a reference to `v`,
* either a read (when `k` is `SsaActualRead()`), an SSA definition (when `k`
* is `SsaDef()`), or a phi-read (when `k` is `SsaPhiRead()`).
*
* Unlike `Liveness::varRef`, this includes `phi` (read) nodes.
*/
pragma[nomagic]
deprecated predicate ssaRef(BasicBlock bb, int i, SourceVariable v, SsaRefKind k) {
variableRead(bb, i, v, _) and
k = SsaActualRead()
or
any(Definition def).definesAt(v, bb, i) and
k = SsaDef()
or
synthPhiRead(bb, v) and i = -1 and k = SsaPhiRead()
}
/**
* Holds if the `i`th node of basic block `bb` is a reference to `v`, and
* this reference is not a phi-read.
*/
deprecated predicate ssaRefNonPhiRead(BasicBlock bb, int i, SourceVariable v) {
ssaRef(bb, i, v, [SsaActualRead().(TSsaRefKind), SsaDef()])
}
deprecated private newtype OrderedSsaRefIndex =
deprecated MkOrderedSsaRefIndex(int i, SsaRefKind k) { ssaRef(_, i, _, k) }
deprecated private OrderedSsaRefIndex ssaRefOrd(
BasicBlock bb, int i, SourceVariable v, SsaRefKind k, int ord
) {
ssaRef(bb, i, v, k) and
result = MkOrderedSsaRefIndex(i, k) and
ord = k.getOrder()
}
/**
* Gets the (1-based) rank of the reference to `v` at the `i`th node of basic
* block `bb`, which has the given reference kind `k`.
*
* For example, if `bb` is a basic block with a phi node for `v` (considered
* to be at index -1), reads `v` at node 2, and defines it at node 5, we have:
*
* ```ql
* ssaRefRank(bb, -1, v, SsaDef()) = 1 // phi node
* ssaRefRank(bb, 2, v, Read()) = 2 // read at node 2
* ssaRefRank(bb, 5, v, SsaDef()) = 3 // definition at node 5
* ```
*
* Reads are considered before writes when they happen at the same index.
*/
deprecated int ssaRefRank(BasicBlock bb, int i, SourceVariable v, SsaRefKind k) {
ssaRefOrd(bb, i, v, k, _) =
rank[result](int j, int ord, OrderedSsaRefIndex res |
res = ssaRefOrd(bb, j, v, _, ord)
|
res order by j, ord
)
}
deprecated int maxSsaRefRank(BasicBlock bb, SourceVariable v) {
result = ssaRefRank(bb, _, v, _) and
not result + 1 = ssaRefRank(bb, _, v, _)
}
/**
* Holds if the SSA definition `def` reaches rank index `rnk` in its own
* basic block `bb`.
*/
deprecated predicate ssaDefReachesRank(
BasicBlock bb, DefinitionExt def, int rnk, SourceVariable v
) {
exists(int i |
rnk = ssaRefRank(bb, i, v, ssaDefExt()) and
def.definesAt(v, bb, i, _)
)
or
ssaDefReachesRank(bb, def, rnk - 1, v) and
rnk = ssaRefRank(bb, _, v, SsaActualRead())
}
/**
* Holds if the SSA definition of `v` at `def` reaches index `i` in the same
* basic block `bb`, without crossing another SSA definition of `v`.
*/
deprecated predicate ssaDefReachesReadWithinBlock(
SourceVariable v, DefinitionExt def, BasicBlock bb, int i
) {
exists(int rnk |
ssaDefReachesRank(bb, def, rnk, v) and
rnk = ssaRefRank(bb, i, v, SsaActualRead())
)
}
/**
* Same as `ssaRefRank()`, but restricted to a particular SSA definition `def`.
*/
deprecated int ssaDefRank(
DefinitionExt def, SourceVariable v, BasicBlock bb, int i, SsaRefKind k
) {
result = ssaRefRank(bb, i, v, k) and
(
ssaDefReachesReadExt(v, def, bb, i)
or
def.definesAt(v, bb, i, k)
)
}
/**
* Holds if the reference to `def` at index `i` in basic block `bb` is the
* last reference to `v` inside `bb`.
*/
pragma[noinline]
deprecated predicate lastSsaRefExt(DefinitionExt def, SourceVariable v, BasicBlock bb, int i) {
ssaDefRank(def, v, bb, i, _) = maxSsaRefRank(bb, v)
}
/** Gets a phi-read node into which `inp` is an input, if any. */
pragma[nomagic]
deprecated private DefinitionExt getAPhiReadOutput(DefinitionExt inp) {
phiHasInputFromBlockExt(result.(PhiReadNode), inp, _)
}
pragma[nomagic]
deprecated DefinitionExt getAnUltimateOutput(Definition def) {
result = getAPhiReadOutput*(def)
}
/**
* Same as `lastSsaRefExt`, but ignores phi-reads.
*/
pragma[noinline]
deprecated predicate lastSsaRef(Definition def, SourceVariable v, BasicBlock bb, int i) {
lastSsaRefExt(getAnUltimateOutput(def), v, bb, i) and
ssaRefNonPhiRead(bb, i, v)
}
deprecated predicate defOccursInBlock(
DefinitionExt def, BasicBlock bb, SourceVariable v, SsaRefKind k
) {
exists(ssaDefRank(def, v, bb, _, k))
}
pragma[noinline]
deprecated predicate ssaDefReachesThroughBlock(DefinitionExt def, BasicBlock bb) {
exists(SourceVariable v |
ssaDefReachesEndOfBlockExt0(bb, def, v) and
not defOccursInBlock(_, bb, v, _)
)
}
/**
* Holds if `def` is accessed in basic block `bb1` (either a read or a write),
* `bb2` is a transitive successor of `bb1`, `def` is live at the end of _some_
* predecessor of `bb2`, and the underlying variable for `def` is neither read
* nor written in any block on the path between `bb1` and `bb2`.
*/
pragma[nomagic]
deprecated predicate varBlockReachesExt(
DefinitionExt def, SourceVariable v, BasicBlock bb1, BasicBlock bb2
) {
defOccursInBlock(def, bb1, v, _) and
bb2 = bb1.getASuccessor()
or
exists(BasicBlock mid |
varBlockReachesExt(def, v, bb1, mid) and
ssaDefReachesThroughBlock(def, mid) and
bb2 = mid.getASuccessor()
)
}
pragma[nomagic]
deprecated private predicate phiReadStep(
DefinitionExt def, PhiReadNode phi, BasicBlock bb1, BasicBlock bb2
) {
exists(SourceVariable v |
varBlockReachesExt(pragma[only_bind_into](def), v, bb1, pragma[only_bind_into](bb2)) and
phi.definesAt(v, bb2, _, _) and
not varRef(bb2, _, v, _)
)
}
pragma[nomagic]
deprecated private predicate varBlockReachesExclPhiRead(
DefinitionExt def, SourceVariable v, BasicBlock bb1, BasicBlock bb2
) {
varBlockReachesExt(def, v, bb1, bb2) and
ssaRefNonPhiRead(bb2, _, v)
or
exists(PhiReadNode phi, BasicBlock mid |
varBlockReachesExclPhiRead(phi, v, mid, bb2) and
phiReadStep(def, phi, bb1, mid)
)
}
/**
* Same as `varBlockReachesExt`, but ignores phi-reads, and furthermore
* `bb2` is restricted to blocks in which the underlying variable `v` of
* `def` is referenced (either a read or a write).
*/
pragma[nomagic]
deprecated predicate varBlockReachesRef(
Definition def, SourceVariable v, BasicBlock bb1, BasicBlock bb2
) {
varBlockReachesExclPhiRead(getAnUltimateOutput(def), v, bb1, bb2) and
ssaRefNonPhiRead(bb1, _, v)
}
pragma[nomagic]
deprecated predicate defAdjacentReadExt(
DefinitionExt def, BasicBlock bb1, BasicBlock bb2, int i2
) {
exists(SourceVariable v |
varBlockReachesExt(def, v, bb1, bb2) and
ssaRefRank(bb2, i2, v, SsaActualRead()) = 1
)
}
pragma[nomagic]
deprecated predicate defAdjacentRead(Definition def, BasicBlock bb1, BasicBlock bb2, int i2) {
exists(SourceVariable v | varBlockReachesRef(def, v, bb1, bb2) |
ssaRefRank(bb2, i2, v, SsaActualRead()) = 1
or
ssaRefRank(bb2, _, v, SsaPhiRead()) = 1 and
ssaRefRank(bb2, i2, v, SsaActualRead()) = 2
)
}
/**
* Holds if `def` is accessed in basic block `bb` (either a read or a write),
* `bb` can reach a transitive successor `bb2` where `def` is no longer live,
* and `v` is neither read nor written in any block on the path between `bb`
* and `bb2`.
*/
pragma[nomagic]
deprecated predicate varBlockReachesExitExt(DefinitionExt def, BasicBlock bb) {
exists(BasicBlock bb2 | varBlockReachesExt(def, _, bb, bb2) |
not defOccursInBlock(def, bb2, _, _) and
not ssaDefReachesEndOfBlockExt0(bb2, def, _)
)
}
pragma[nomagic]
deprecated private predicate varBlockReachesExitExclPhiRead(DefinitionExt def, BasicBlock bb) {
exists(BasicBlock bb2, SourceVariable v |
varBlockReachesExt(def, v, bb, bb2) and
not defOccursInBlock(def, bb2, _, _) and
not ssaDefReachesEndOfBlockExt0(bb2, def, _) and
not any(PhiReadNode phi).definesAt(v, bb2, _, _)
)
or
exists(PhiReadNode phi, BasicBlock bb2 |
varBlockReachesExitExclPhiRead(phi, bb2) and
phiReadStep(def, phi, bb, bb2)
)
}
/**
* Same as `varBlockReachesExitExt`, but ignores phi-reads.
*/
pragma[nomagic]
deprecated predicate varBlockReachesExit(Definition def, BasicBlock bb) {
varBlockReachesExitExclPhiRead(getAnUltimateOutput(def), bb)
}
}
private import SsaDefReaches
pragma[nomagic]
deprecated private predicate liveThroughExt(BasicBlock bb, SourceVariable v) {
liveAtExit(bb, v) and
not ssaRef(bb, _, v, ssaDefExt())
}
/**
* NB: If this predicate is exposed, it should be cached.
*
* Holds if the SSA definition of `v` at `def` reaches the end of basic
* block `bb`, at which point it is still live, without crossing another
* SSA definition of `v`.
*/
pragma[nomagic]
deprecated private predicate ssaDefReachesEndOfBlockExt0(
BasicBlock bb, DefinitionExt def, SourceVariable v
) {
exists(int last |
last = maxSsaRefRank(pragma[only_bind_into](bb), pragma[only_bind_into](v)) and
ssaDefReachesRank(bb, def, last, v) and
liveAtExit(bb, v)
)
or
// The construction of SSA form ensures that each read of a variable is
// dominated by its definition. An SSA definition therefore reaches a
// control flow node if it is the _closest_ SSA definition that dominates
// the node. If two definitions dominate a node then one must dominate the
// other, so therefore the definition of _closest_ is given by the dominator
// tree. Thus, reaching definitions can be calculated in terms of dominance.
ssaDefReachesEndOfBlockExt0(bb.getImmediateDominator(), def, pragma[only_bind_into](v)) and
liveThroughExt(bb, pragma[only_bind_into](v))
}
deprecated predicate ssaDefReachesEndOfBlockExt = ssaDefReachesEndOfBlockExt0/3;
/**
* NB: If this predicate is exposed, it should be cached.
*
* Same as `ssaDefReachesEndOfBlockExt`, but ignores phi-reads.
*/
predicate ssaDefReachesEndOfBlock = SsaDefReachesNew::ssaDefReachesEndOfBlock/3;
/**
* NB: If this predicate is exposed, it should be cached.
*
* Holds if `inp` is an input to the phi node `phi` along the edge originating in `bb`.
*/
pragma[nomagic]
predicate phiHasInputFromBlock(PhiNode phi, Definition inp, BasicBlock bb) {
exists(SourceVariable v, BasicBlock bbDef |
phi.definesAt(v, bbDef, _) and
getABasicBlockPredecessor(bbDef) = bb and
ssaDefReachesEndOfBlock(bb, inp, v)
)
}
/**
* NB: If this predicate is exposed, it should be cached.
*
* Holds if `inp` is an input to the phi (read) node `phi` along the edge originating in `bb`.
*/
pragma[nomagic]
deprecated predicate phiHasInputFromBlockExt(DefinitionExt phi, DefinitionExt inp, BasicBlock bb) {
exists(SourceVariable v, BasicBlock bbDef |
phi.definesAt(v, bbDef, _, _) and
getABasicBlockPredecessor(bbDef) = bb and
ssaDefReachesEndOfBlockExt0(bb, inp, v)
|
phi instanceof PhiNode or
phi instanceof PhiReadNode
)
}
/**
* NB: If this predicate is exposed, it should be cached.
*
* Holds if the SSA definition of `v` at `def` reaches a read at index `i` in
* basic block `bb`, without crossing another SSA definition of `v`.
*/
pragma[nomagic]
deprecated predicate ssaDefReachesReadExt(
SourceVariable v, DefinitionExt def, BasicBlock bb, int i
) {
ssaDefReachesReadWithinBlock(v, def, bb, i)
or
ssaRef(bb, i, v, SsaActualRead()) and
ssaDefReachesEndOfBlockExt0(getABasicBlockPredecessor(bb), def, v) and
not ssaDefReachesReadWithinBlock(v, _, bb, i)
}
/**
* NB: If this predicate is exposed, it should be cached.
*
* Same as `ssaDefReachesReadExt`, but ignores phi-reads.
*/
predicate ssaDefReachesRead(SourceVariable v, Definition def, BasicBlock bb, int i) {
SsaDefReachesNew::ssaDefReachesRead(v, def, bb, i) and
variableRead(bb, i, v, _)
}
/**
* NB: If this predicate is exposed, it should be cached.
*
* Holds if `def` is accessed at index `i1` in basic block `bb1` (either a read
* or a write), `def` is read at index `i2` in basic block `bb2`, and there is a
* path between them without any read of `def`.
*/
pragma[nomagic]
deprecated predicate adjacentDefReadExt(
DefinitionExt def, SourceVariable v, BasicBlock bb1, int i1, BasicBlock bb2, int i2
) {
exists(int rnk |
rnk = ssaDefRank(def, v, bb1, i1, _) and
rnk + 1 = ssaDefRank(def, v, bb1, i2, SsaActualRead()) and
variableRead(bb1, i2, v, _) and
bb2 = bb1
)
or
lastSsaRefExt(def, v, bb1, i1) and
defAdjacentReadExt(def, bb1, bb2, i2)
}
/**
* NB: If this predicate is exposed, it should be cached.
*
* Same as `adjacentDefReadExt`, but ignores phi-reads.
*/
pragma[nomagic]
deprecated predicate adjacentDefRead(
Definition def, BasicBlock bb1, int i1, BasicBlock bb2, int i2
) {
exists(SourceVariable v |
adjacentDefReadExt(getAnUltimateOutput(def), v, bb1, i1, bb2, i2) and
ssaRefNonPhiRead(bb1, i1, v)
)
or
lastSsaRef(def, _, bb1, i1) and
defAdjacentRead(def, bb1, bb2, i2)
}
deprecated private predicate lastRefRedefExtSameBlock(
DefinitionExt def, SourceVariable v, BasicBlock bb, int i, DefinitionExt next
) {
exists(int rnk, int j |
rnk = ssaDefRank(def, v, bb, i, _) and
next.definesAt(v, bb, j, _) and
rnk + 1 = ssaRefRank(bb, j, v, ssaDefExt())
)
}
/**
* NB: If this predicate is exposed, it should be cached.
*