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C++: allow phi nodes to self-bound

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This commit is contained in:
Robert Marsh
2018-12-13 11:55:55 -08:00
parent b2cd9a29f2
commit 567eee1114
3 changed files with 20 additions and 5 deletions
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9
cpp/ql/src/semmle/code/cpp/rangeanalysis/RangeAnalysis.qll
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@@ -118,7 +118,7 @@ private import RangeAnalysisCache
import RangeAnalysisPublic
/**
* Gets a condition that tests whether `op` equals `bound + delta`.
* Gets a condition that tests whether `vn` equals `bound + delta`.
*
* If the condition evaluates to `testIsTrue`:
* - `isEq = true` : `i == bound + delta`
@@ -151,11 +151,11 @@ private predicate boundFlowStepSsa(
}
/**
* Gets a condition that tests whether `op` is bounded by `bound + delta`.
* Gets a condition that tests whether `vn` is bounded by `bound + delta`.
*
* If the condition evaluates to `testIsTrue`:
* - `upper = true` : `op <= bound + delta`
* - `upper = false` : `op >= bound + delta`
* - `upper = true` : `vn <= bound + delta`
* - `upper = false` : `vn >= bound + delta`
*/
private IRGuardCondition boundFlowCond(ValueNumber vn, NonPhiOperand bound, int delta, boolean upper,
boolean testIsTrue)
@@ -549,7 +549,6 @@ private predicate boundedInstruction(
boundedPhiCandValidForEdge(i, b, delta, upper, fromBackEdge, origdelta, reason, op)
)
or
not i instanceof PhiInstruction and
i = b.getInstruction(delta) and
(upper = true or upper = false) and
fromBackEdge = false and

3
cpp/ql/test/library-tests/rangeanalysis/rangeanalysis/RangeAnalysis.expected
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@@ -35,3 +35,6 @@
| test.cpp:97:10:97:10 | Load: x | file://:0:0:0:0 | 0 | 1 | false | CompareLT: ... < ... | test.cpp:94:7:94:11 | test.cpp:94:7:94:11 |
| test.cpp:100:10:100:10 | Load: x | file://:0:0:0:0 | 0 | 1 | true | CompareLE: ... <= ... | test.cpp:99:7:99:12 | test.cpp:99:7:99:12 |
| test.cpp:102:10:102:10 | Load: x | file://:0:0:0:0 | 0 | 2 | false | CompareLE: ... <= ... | test.cpp:99:7:99:12 | test.cpp:99:7:99:12 |
| test.cpp:106:5:106:10 | Phi: test10 | test.cpp:113:3:113:6 | Phi: call to sink | -1 | true | CompareLT: ... < ... | test.cpp:114:18:114:22 | test.cpp:114:18:114:22 |
| test.cpp:106:5:106:10 | Phi: test10 | test.cpp:114:18:114:18 | Phi: i | 0 | false | NoReason | file://:0:0:0:0 | file://:0:0:0:0 |
| test.cpp:106:5:106:10 | Phi: test10 | test.cpp:114:18:114:18 | Phi: i | 0 | true | NoReason | file://:0:0:0:0 | file://:0:0:0:0 |

13
cpp/ql/test/library-tests/rangeanalysis/rangeanalysis/test.cpp
View File

@@ -102,3 +102,16 @@ void test9(int x) {
sink(x);
}
}
int test10(int y, int z, bool use_y) {
int x;
if(use_y) {
x = y;
} else {
x = z;
}
sink();
for(int i = 0; i < x; i++) {
return i;
}
}