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Bug 394521 Do Constant folding propagation when building CFG

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When building control flow graph we can consider constants
and not add some branches in decisions nodes, that make CFG
more accurate and elimate some false positives

Change-Id: I19c623e1e6d2dc7416a0e796a98168df7a976111
Signed-off-by: Alena Laskavaia <elaskavaia.cdt@gmail.com>
Reviewed-on: https://git.eclipse.org/r/28726
This commit is contained in:
Alena Laskavaia 2014-06-18 22:12:15 -04:00 • committed by Elena Laskavaia
parent 3d78256606
commit db43e03878
3 changed files with 94 additions and 5 deletions
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31
codan/org.eclipse.cdt.codan.core.cxx/src/org/eclipse/cdt/codan/core/cxx/internal/model/cfg/ControlFlowGraphBuilder.java
View file

@ -52,8 +52,10 @@ import org.eclipse.cdt.core.dom.ast.IASTStatement;
import org.eclipse.cdt.core.dom.ast.IASTSwitchStatement;
import org.eclipse.cdt.core.dom.ast.IASTUnaryExpression;
import org.eclipse.cdt.core.dom.ast.IASTWhileStatement;
import org.eclipse.cdt.core.dom.ast.IValue;
import org.eclipse.cdt.core.dom.ast.cpp.ICPPASTCatchHandler;
import org.eclipse.cdt.core.dom.ast.cpp.ICPPASTTryBlockStatement;
import org.eclipse.cdt.internal.core.dom.parser.Value;
/**
* This class creates C control flow graph
@ -463,14 +465,37 @@ public class ControlFlowGraphBuilder {
if (prev instanceof IExitNode || prev == null) {
dead.add(node);
return;
} else if (prev instanceof ICfgData) {
if (prev instanceof IDecisionNode && !(node instanceof IBranchNode)) {
}
if (prev instanceof IDecisionNode) {
if (node instanceof IBranchNode) {
IDecisionNode decisionNode = (IDecisionNode) prev;
if (isConstant(decisionNode, 1) && ((IBranchNode) node).getLabel().equals(IBranchNode.ELSE)) {
dead.add(node);
return;
} else if (isConstant(decisionNode, 0) && ((IBranchNode) node).getLabel().equals(IBranchNode.THEN)) {
dead.add(node);
return;
}
} else {
dead.add(node);
return;
}
((AbstractBasicBlock) prev).addOutgoing(node);
}
((AbstractBasicBlock) prev).addOutgoing(node);
if (!(node instanceof IStartNode))
((AbstractBasicBlock) node).addIncoming(prev);
}
private boolean isConstant(IDecisionNode node, long testvalue) {
if (node instanceof ICfgData) {
IASTNode ast = (IASTNode) ((ICfgData) node).getData();
if (ast instanceof IASTExpression) {
IValue dvalue = Value.create((IASTExpression) ast, 5);
Long numericalValue = dvalue.numericalValue();
if (numericalValue==null) return false;
return (numericalValue==testvalue);
}
}
return false;
}
}

46
codan/org.eclipse.cdt.codan.core.test/src/org/eclipse/cdt/codan/core/cfg/ControlFlowGraphTest.java
View file

@ -294,8 +294,8 @@ public class ControlFlowGraphTest extends CodanFastCxxAstTestCase {
assertEquals(1, graph.getUnconnectedNodeSize());
}
// foo() {
// int a=10, x=5;
// foo(int x) {
// int a=10;
// if (a--) {
// if (x<0)
// a++;
@ -408,4 +408,46 @@ public class ControlFlowGraphTest extends CodanFastCxxAstTestCase {
IStartNode startNode = graph.getStartNode();
assertEquals(1, graph.getUnconnectedNodeSize());
}
// foo() {
// int a=10,x=5;
// if (x<0)
// a++;
// }
public void test_deadbranch() {
buildCfg(getAboveComment(), false);
checkCfg(false);
IStartNode startNode = graph.getStartNode();
IPlainNode decl = (IPlainNode) startNode.getOutgoing();
IDecisionNode des = (IDecisionNode) decl.getOutgoing();
assertEquals("x<0", data(des));
IBasicBlock bElse = branchEnd(des, IBranchNode.ELSE);
IBasicBlock m2 = jumpEnd(branchEnd(des, IBranchNode.THEN));
IBasicBlock m1 = jumpEnd(bElse);
assertNull(m2);
assertNotNull(m1);
}
// int test1_f()
// {
// while (1)
// {
// }
// }
public void test_infiniloop() {
buildCfg(getAboveComment(), false);
checkCfg(false);
IStartNode startNode = graph.getStartNode();
IConnectorNode conn = (IConnectorNode) startNode.getOutgoing();
IDecisionNode des = (IDecisionNode) conn.getOutgoing();
assertEquals("1", data(des));
IBasicBlock bElse = branchEnd(des, IBranchNode.ELSE);
IBasicBlock bThen = branchEnd(des, IBranchNode.THEN);
IBasicBlock m2 = jumpEnd(bThen);
IBasicBlock m1 = jumpEnd(bElse);
assertNotNull(m2);
assertNull(m1);
}
}

22
codan/org.eclipse.cdt.codan.core.test/src/org/eclipse/cdt/codan/core/internal/checkers/ReturnCheckerTest.java
View file

@ -384,4 +384,26 @@ public class ReturnCheckerTest extends CheckerTestCase {
checkNoErrors();
}
// int test1() {
// do {
// return 1;
// } while (0);
// }
public void testNoRetInfinitLoop() throws Exception {
// Bug 394521
loadCodeAndRunCpp(getAboveComment());
checkNoErrors();
}
// int test1_f() // WARNING HERE: "No return, in function returning non-void"
// {
// while (1)
// {
// }
// }
public void testNoRetInfinitLoop2() throws Exception {
// Bug 394521
loadCodeAndRunCpp(getAboveComment());
checkNoErrors();
}
}