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[analyzer] LoopUnrolling: check the bitwidth of the used numbers (pr34943) 

The loop unrolling feature aims to track the maximum possible steps a loop can
make. In order to implement this, it investigates the initial value of the 
counter variable and the bound number. (It has to be known.)
These numbers are used as llvm::APInts, however, it was not checked if their
bitwidths are the same which lead to some crashes.
This revision solves this problem by extending the "shorter" one (to the length
of the "longer" one).
For the detailed bug report, see: https://bugs.llvm.org/show_bug.cgi?id=34943

Differential Revision: https://reviews.llvm.org/D38922

llvm-svn: 316830
This commit is contained in:
Peter Szecsi 2017-10-28 12:19:08 +00:00
parent 39cfdc664d
commit 1496d188a0
2 changed files with 15 additions and 2 deletions
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11
clang/lib/StaticAnalyzer/Core/LoopUnrolling.cpp
View File

@ -208,9 +208,16 @@ bool shouldCompletelyUnroll(const Stmt *LoopStmt, ASTContext &ASTCtx,
return false;
auto CounterVar = Matches[0].getNodeAs<VarDecl>("initVarName");
auto BoundNum = Matches[0].getNodeAs<IntegerLiteral>("boundNum")->getValue();
auto InitNum = Matches[0].getNodeAs<IntegerLiteral>("initNum")->getValue();
llvm::APInt BoundNum =
Matches[0].getNodeAs<IntegerLiteral>("boundNum")->getValue();
llvm::APInt InitNum =
Matches[0].getNodeAs<IntegerLiteral>("initNum")->getValue();
auto CondOp = Matches[0].getNodeAs<BinaryOperator>("conditionOperator");
if (InitNum.getBitWidth() != BoundNum.getBitWidth()) {
InitNum = InitNum.zextOrSelf(BoundNum.getBitWidth());
BoundNum = BoundNum.zextOrSelf(InitNum.getBitWidth());
}
if (CondOp->getOpcode() == BO_GE || CondOp->getOpcode() == BO_LE)
maxStep = (BoundNum - InitNum + 1).abs().getZExtValue();
else

6
clang/test/Analysis/loop-unrolling.cpp
View File

@ -373,3 +373,9 @@ int num_steps_over_limit3() {
return 0;
}
void pr34943() {
for (int i = 0; i < 6L; ++i) {
clang_analyzer_numTimesReached(); // expected-warning {{6}}
}
}