[PATCH] D39682: [analyzer] Fix a crash on logical operators with vectors.

[Artem Dergachev via Phabricator via cfe-commits]

NoQ created this revision.

We crash whenever we try to compute `x && y` or `x || y` where `x` and `y` are of vector type.

For now we do not seem to properly model operations with vectors. In particular, operations `&&` and `||` on two values of type `int __attribute__((ext_vector_type(2)))` are not short-circuit, unlike regular logical operators, so even our CFG is incorrect.

Avoid the crash, add respective FIXME tests for later.


https://reviews.llvm.org/D39682

Files:
  lib/StaticAnalyzer/Core/ExprEngineC.cpp
  test/Analysis/vector.c


Index: test/Analysis/vector.c
===================================================================
--- /dev/null
+++ test/Analysis/vector.c
@@ -0,0 +1,28 @@
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,debug.ExprInspection -verify %s
+
+typedef int __attribute__((ext_vector_type(2))) V;
+
+void clang_analyzer_numTimesReached();
+void clang_analyzer_eval(int);
+
+int flag;
+
+V pass_through_and_set_flag(V v) {
+  flag = 1;
+  return v;
+}
+
+V no_crash(V x, V y) {
+  flag = 0;
+  V z = x && pass_through_and_set_flag(y);
+  clang_analyzer_eval(flag); // expected-warning{{TRUE}}
+  // FIXME: For now we treat vector operator && as short-circuit,
+  // but in fact it is not. It should always evaluate
+  // pass_through_and_set_flag(). It should not split state.
+  // Now we also get FALSE on the other path.
+  // expected-warning at -5{{FALSE}}
+
+  // FIXME: Should be 1 since we should not split state.
+  clang_analyzer_numTimesReached(); // expected-warning{{2}}
+  return z;
+}
Index: lib/StaticAnalyzer/Core/ExprEngineC.cpp
===================================================================
--- lib/StaticAnalyzer/Core/ExprEngineC.cpp
+++ lib/StaticAnalyzer/Core/ExprEngineC.cpp
@@ -625,6 +625,17 @@
   assert(B->getOpcode() == BO_LAnd ||
          B->getOpcode() == BO_LOr);
 
+  if (B->getType()->isVectorType()) {
+    // FIXME: We do not model vector arithmetic yet. When adding support for
+    // that, note that the CFG-based reasoning below does not apply, because
+    // logical operators on vectors are not short-circuit. Currently they are
+    // modeled as short-circuit in Clang CFG but this is incorrect.
+    StmtNodeBuilder Bldr(Pred, Dst, *currBldrCtx);
+    // Do not set the value for the expression. It'd be UnknownVal by default.
+    Bldr.generateNode(B, Pred, Pred->getState());
+    return;
+  }
+
   StmtNodeBuilder Bldr(Pred, Dst, *currBldrCtx);
   ProgramStateRef state = Pred->getState();
 


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D39682.121720.patch
Type: text/x-patch
Size: 1937 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20171106/652ff471/attachment.bin>