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C++: A few small refactors to the simple range analysis library #20691

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Merged
paldepind merged 5 commits into from
Oct 27, 2025
Merged

C++: A few small refactors to the simple range analysis library #20691

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17e0dec
C++: Add toString for RelationStrictness
paldepind Oct 24, 2025
3af9885
C++: Fix typos in tests
paldepind Oct 24, 2025
383e6a4
C++: Use `or` instead of `if`
paldepind Oct 24, 2025
5709964
C++: Simplify boundFromGuard
paldepind Oct 24, 2025
d1ea1af
C++: Make small trivial tweaks
paldepind Oct 24, 2025
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8 changes: 4 additions & 4 deletions cpp/ql/lib/semmle/code/cpp/rangeanalysis/RangeAnalysisUtils.qll
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Original file line number Diff line number Diff line change
Expand Up @@ -118,10 +118,10 @@ predicate relOpWithSwap(
*
* This allows for the relation to be either as written, or with its
* arguments reversed; for example, if `rel` is `x < 5` then
* `relOpWithSwapAndNegate(rel, x, 5, Lesser(), Strict(), true)`,
* `relOpWithSwapAndNegate(rel, 5, x, Greater(), Strict(), true)`,
* `relOpWithSwapAndNegate(rel, x, 5, Greater(), Nonstrict(), false)` and
* `relOpWithSwapAndNegate(rel, 5, x, Lesser(), Nonstrict(), false)` hold.
* - `relOpWithSwapAndNegate(rel, x, 5, Lesser(), Strict(), true)`,
* - `relOpWithSwapAndNegate(rel, 5, x, Greater(), Strict(), true)`,
* - `relOpWithSwapAndNegate(rel, x, 5, Greater(), Nonstrict(), false)` and
* - `relOpWithSwapAndNegate(rel, 5, x, Lesser(), Nonstrict(), false)` hold.
*/
predicate relOpWithSwapAndNegate(
RelationalOperation rel, Expr a, Expr b, RelationDirection dir, RelationStrictness strict,
Expand Down
14 changes: 5 additions & 9 deletions cpp/ql/lib/semmle/code/cpp/rangeanalysis/SimpleRangeAnalysis.qll
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Expand Up @@ -1213,7 +1213,7 @@ private float getLowerBoundsImpl(Expr expr) {
// equal to `min(-y + 1,y - 1)`.
exists(float childLB |
childLB = getFullyConvertedLowerBounds(remExpr.getAnOperand()) and
not childLB >= 0
childLB < 0
|
result = getFullyConvertedLowerBounds(remExpr.getRightOperand()) - 1
or
Expand Down Expand Up @@ -1425,8 +1425,7 @@ private float getUpperBoundsImpl(Expr expr) {
// adding `-rhsLB` to the set of upper bounds.
exists(float rhsLB |
rhsLB = getFullyConvertedLowerBounds(remExpr.getRightOperand()) and
not rhsLB >= 0
|
rhsLB < 0 and
result = -rhsLB + 1
)
)
Expand Down Expand Up @@ -1571,8 +1570,7 @@ private float getPhiLowerBounds(StackVariable v, RangeSsaDefinition phi) {
exists(VariableAccess access, Expr guard, boolean branch, float defLB, float guardLB |
phi.isGuardPhi(v, access, guard, branch) and
lowerBoundFromGuard(guard, access, guardLB, branch) and
defLB = getFullyConvertedLowerBounds(access)
|
defLB = getFullyConvertedLowerBounds(access) and
// Compute the maximum of `guardLB` and `defLB`.
if guardLB > defLB then result = guardLB else result = defLB
)
Expand All @@ -1596,8 +1594,7 @@ private float getPhiUpperBounds(StackVariable v, RangeSsaDefinition phi) {
exists(VariableAccess access, Expr guard, boolean branch, float defUB, float guardUB |
phi.isGuardPhi(v, access, guard, branch) and
upperBoundFromGuard(guard, access, guardUB, branch) and
defUB = getFullyConvertedUpperBounds(access)
|
defUB = getFullyConvertedUpperBounds(access) and
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@geoffw0 geoffw0 Oct 27, 2025

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For what reason do you prefer and over | here?

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@paldepind paldepind Oct 27, 2025 •
edited
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In my experience | is usually used for some reason. Either because there is an or afterwards or because the thing before and after are somehow different. Here there doesn't seem to be any reason, so going with the default and seems clearer :)

// Compute the minimum of `guardUB` and `defUB`.
if guardUB < defUB then result = guardUB else result = defUB
)
Expand Down Expand Up @@ -1761,8 +1758,7 @@ private predicate upperBoundFromGuard(Expr guard, VariableAccess v, float ub, bo
}

/**
* This predicate simplifies the results returned by
* `linearBoundFromGuard`.
* This predicate simplifies the results returned by `linearBoundFromGuard`.
*/
private predicate boundFromGuard(
Expr guard, VariableAccess v, float boundValue, boolean isLowerBound,
Expand Down
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