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C++: add comments and private annotations

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This commit is contained in:
Robert Marsh
2019-07-15 14:47:21 -07:00
parent 86a018b0b4
commit 1f17cfb8ad
1 changed files with 19 additions and 7 deletions
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26
cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/AliasedSSA.qll
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@@ -229,7 +229,21 @@ Overlap getOverlap(MemoryLocation def, MemoryLocation use) {
)
}
predicate isRelevantOffset(VirtualVariable vv, IntValue offset) {
/*
* The following predicates compute the overlap relation between `VariableMemoryLocation`s in the
* same `VirtualVariable` as follows:
* 1. Compute the set of offsets within each virtual variable in `isRelevantOffset` (linear in
* the number of VMLs)
* 2. Compute the set of offsets that each VML with known start and end offsets covers in
* `isCoveredOffset` (this is currently quadratic in the number of VMLs in a VVar, but
* could be optimized further. The quadratic portion is never materialized, and it seems to
* be performant in practice)
* 3. In `getVariableMemoryLocationOverlap`, compute the set of overlapping pairs of VMLs using a
* join on `isCoveredOffset` (linear in the size of the overlap set)
* 4. In `getVariableMemoryLocationOverlap`, compute the precise overlap relation for each
* overlapping pair of VMLs (linear in the size of the overlap set)
*/
private predicate isRelevantOffset(VirtualVariable vv, IntValue offset) {
exists(VariableMemoryLocation ml |
ml.getVirtualVariable() = vv
|
@@ -239,12 +253,12 @@ predicate isRelevantOffset(VirtualVariable vv, IntValue offset) {
)
}
predicate isRelatableMemoryLocation(VariableMemoryLocation vml) {
private predicate isRelatableMemoryLocation(VariableMemoryLocation vml) {
vml.getEndBitOffset() != Ints::unknown() and
vml.getStartBitOffset() != Ints::unknown()
}
predicate isCoveredOffset(VariableMemoryLocation vml, VirtualVariable vv, IntValue offset) {
private predicate isCoveredOffset(VariableMemoryLocation vml, VirtualVariable vv, IntValue offset) {
isRelevantOffset(vv, offset) and
vv = vml.getVirtualVariable() and
isRelatableMemoryLocation(vml) and
@@ -252,7 +266,7 @@ predicate isCoveredOffset(VariableMemoryLocation vml, VirtualVariable vv, IntVal
offset <= vml.getEndBitOffset()
}
predicate hasUnknownOffset(VariableMemoryLocation vml, VirtualVariable vv) {
private predicate hasUnknownOffset(VariableMemoryLocation vml, VirtualVariable vv) {
vml.getVirtualVariable() = vv and
(
vml.getStartBitOffset() = Ints::unknown() or
@@ -260,9 +274,7 @@ predicate hasUnknownOffset(VariableMemoryLocation vml, VirtualVariable vv) {
)
}
Overlap getVariableMemoryLocationOverlap(VariableMemoryLocation def, VariableMemoryLocation use) {
private Overlap getVariableMemoryLocationOverlap(VariableMemoryLocation def, VariableMemoryLocation use) {
def.getVariable() = use.getVariable() and
(
exists(VirtualVariable vv, IntValue offset | isCoveredOffset(def, vv, offset) and isCoveredOffset(use, vv, offset))