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C++: Drive-by join order fix. Before:

Browse Source 
```
Evaluated relational algebra for predicate SsaInternals::getDefImpl/1#1ed4f567@65628fbv with tuple counts:
          4935102  ~5%    {4} r1 = SCAN `SsaInternals::SsaImpl::Definition.definesAt/3#dispred#7eea4c8f` OUTPUT In.2, In.3, In.0, In.1
        104274503  ~1%    {3}    | JOIN WITH `SsaInternals::DefImpl.hasIndexInBlock/2#dispred#30a6c29f_120#join_rhs` ON FIRST 2 OUTPUT Rhs.2, Lhs.3, Lhs.2
          4921319  ~2%    {2}    | JOIN WITH `SsaInternals::DefImpl.getSourceVariable/0#dispred#72437659` ON FIRST 2 OUTPUT Lhs.2, Lhs.0
                          return r1
```
After:
```
Evaluated relational algebra for predicate SsaInternals::SsaImpl::Definition.definesAt/3#dispred#7eea4c8f_1230#join_rhs@b280fb5h with tuple counts:
        4935102  ~3%    {4} r1 = SCAN `SsaInternals::SsaImpl::Definition.definesAt/3#dispred#7eea4c8f` OUTPUT In.1, In.2, In.3, In.0
                        return r1

Evaluated relational algebra for predicate SsaInternals::DefImpl.hasIndexInBlock/3#dispred#31d295aa_1230#join_rhs@2be655s4 with tuple counts:
        5634706  ~1%    {4} r1 = SCAN `SsaInternals::DefImpl.hasIndexInBlock/3#dispred#31d295aa` OUTPUT In.1, In.2, In.3, In.0
                        return r1

Evaluated relational algebra for predicate SsaInternals::getDefImpl/1#1ed4f567@8afa36uu with tuple counts:
        4921319  ~2%    {2} r1 = JOIN `SsaInternals::SsaImpl::Definition.definesAt/3#dispred#7eea4c8f_1230#join_rhs` WITH `SsaInternals::DefImpl.hasIndexInBlock/3#dispred#31d295aa_1230#join_rhs` ON FIRST 3 OUTPUT Lhs.3, Rhs.3
                        return r1
```
This commit is contained in:
Mathias Vorreiter Pedersen
2025-05-13 14:21:28 +01:00
parent 0836f0b413
commit f255fc2fd5
2 changed files with 7 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/DataFlowPrivate.qll
View File

@@ -1567,7 +1567,7 @@ private int countNumberOfBranchesUsingParameter(SwitchInstruction switch, Parame
|
exists(Ssa::UseImpl use | use.hasIndexInBlock(useblock, _, sv))
or
exists(Ssa::DefImpl def | def.hasIndexInBlock(useblock, _, sv))
exists(Ssa::DefImpl def | def.hasIndexInBlock(sv, useblock, _))
)
)
)
@@ -1814,7 +1814,7 @@ module IteratorFlow {
*/
private predicate isIteratorWrite(Instruction write, Operand address) {
exists(Ssa::DefImpl writeDef, IRBlock bb, int i |
writeDef.hasIndexInBlock(bb, i, _) and
writeDef.hasIndexInBlock(_, bb, i) and
bb.getInstruction(i) = write and
address = writeDef.getAddressOperand()
)

9
cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/SsaInternals.qll
View File

@@ -191,7 +191,7 @@ abstract class DefImpl extends TDefImpl {
* Holds if this definition (or use) has index `index` in block `block`,
* and is a definition (or use) of the variable `sv`
*/
final predicate hasIndexInBlock(IRBlock block, int index, SourceVariable sv) {
final predicate hasIndexInBlock(SourceVariable sv, IRBlock block, int index) {
this.hasIndexInBlock(block, index) and
sv = this.getSourceVariable()
}
@@ -891,12 +891,12 @@ private module SsaInput implements SsaImplCommon::InputSig<Location> {
predicate variableWrite(BasicBlock bb, int i, SourceVariable v, boolean certain) {
DataFlowImplCommon::forceCachingInSameStage() and
(
exists(DefImpl def | def.hasIndexInBlock(bb, i, v) |
exists(DefImpl def | def.hasIndexInBlock(v, bb, i) |
if def.isCertain() then certain = true else certain = false
)
or
exists(GlobalDefImpl global |
global.hasIndexInBlock(bb, i, v) and
global.hasIndexInBlock(v, bb, i) and
certain = true
)
)
@@ -934,10 +934,11 @@ module SsaCached {
}
/** Gets the `DefImpl` corresponding to `def`. */
pragma[nomagic]
private DefImpl getDefImpl(SsaImpl::Definition def) {
exists(SourceVariable sv, IRBlock bb, int i |
def.definesAt(sv, bb, i) and
result.hasIndexInBlock(bb, i, sv)
result.hasIndexInBlock(sv, bb, i)
)
}