[analyzer] Fix some expressions staying live too long. Add a debug checker.
StaticAnalyzer uses the CFG-based RelaxedLiveVariables analysis in order to,
in particular, figure out values of which expressions are still needed.
When the expression becomes "dead", it is garbage-collected during
the dead binding scan.
Expressions that constitute branches/bodies of control flow statements,
eg. `E1' in `if (C1) E1;' but not `E2' in `if (C2) { E2; }', were kept alive
for too long. This caused false positives in MoveChecker because it relies
on cleaning up loop-local variables when they go out of scope, but some of those
live-for-too-long expressions were keeping a reference to those variables.
Fix liveness analysis to correctly mark these expressions as dead.
Add a debug checker, debug.DumpLiveStmts, in order to test expressions liveness.
Differential Revision: https://reviews.llvm.org/D55566
llvm-svn: 349320
diff --git a/clang/docs/analyzer/DebugChecks.rst b/clang/docs/analyzer/DebugChecks.rst
index 7b192f6..bb2f37f 100644
--- a/clang/docs/analyzer/DebugChecks.rst
+++ b/clang/docs/analyzer/DebugChecks.rst
@@ -30,9 +30,12 @@
- debug.DumpLiveVars: Show the results of live variable analysis for each
top-level function being analyzed.
+- debug.DumpLiveStmts: Show the results of live statement analysis for each
+ top-level function being analyzed.
+
- debug.ViewExplodedGraph: Show the Exploded Graphs generated for the
analysis of different functions in the input translation unit. When there
- are several functions analyzed, display one graph per function. Beware
+ are several functions analyzed, display one graph per function. Beware
that these graphs may grow very large, even for small functions.
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