Szelethus created this revision.
Szelethus added reviewers: xazax.hun, NoQ, vsavchenko, balazske, martong,
baloghadamsoftware, dcoughlin.
Szelethus added a project: clang.
Herald added subscribers: cfe-commits, ASDenysPetrov, steakhal, Charusso,
gamesh411, dkrupp, donat.nagy, mikhail.ramalho, a.sidorin, rnkovacs, szepet,
whisperity.
I had a bit of fun with the tags.
Liveness analysis calculates the set of live/dead values in the program.
However, statements don't always have a value associated with them, expressions
do. For this reason, I found it puzzling why LivenessAnalysis work with "live
statements", or answers questions such as "is this statement live". After a bit
of digging, I found that the only client of statement liveness is
`EnvironmentManager::removeDeadBindings` (the one modified in this patch), and
the only non-expression statement it queries are `ObjCForCollectionStmt`s, but
no lit tests crashed on the added asserts.
This patch isn't necesserily intended to be committed -- it more of a request
for comments whether it would be safe to change statement liveness to strictly
expression liveness. It would be great, because my ultimate goal is to merge
the implementation of UninitializedVariable and LivenessAnalaysis, and add
Reaching Definitions under the same hood, but the statement liveness was very
much out of place and makes the merge very awkward, if even possible.
I have a number of changes planned, but I didn't want to go too far ahead of
myself, in case I missed something fundamental that justifies statement
liveness as it is.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D82122
Files:
clang/lib/StaticAnalyzer/Core/Environment.cpp
Index: clang/lib/StaticAnalyzer/Core/Environment.cpp
===================================================================
--- clang/lib/StaticAnalyzer/Core/Environment.cpp
+++ clang/lib/StaticAnalyzer/Core/Environment.cpp
@@ -183,12 +183,18 @@
F.getTreeFactory());
// Iterate over the block-expr bindings.
- for (Environment::iterator I = Env.begin(), E = Env.end();
- I != E; ++I) {
+ for (Environment::iterator I = Env.begin(), E = Env.end(); I != E; ++I) {
const EnvironmentEntry &BlkExpr = I.getKey();
const SVal &X = I.getData();
- if (SymReaper.isLive(BlkExpr.getStmt(), BlkExpr.getLocationContext())) {
+ const bool IsBlkExprLive =
+ SymReaper.isLive(BlkExpr.getStmt(), BlkExpr.getLocationContext());
+
+ assert((isa<Expr>(BlkExpr.getStmt()) || !IsBlkExprLive) &&
+ "Only Exprs can be live, LivenessAnalysis argues about the liveness
"
+ "of *values*!");
+
+ if (IsBlkExprLive) {
// Copy the binding to the new map.
EBMapRef = EBMapRef.add(BlkExpr, X);
Index: clang/lib/StaticAnalyzer/Core/Environment.cpp
===================================================================
--- clang/lib/StaticAnalyzer/Core/Environment.cpp
+++ clang/lib/StaticAnalyzer/Core/Environment.cpp
@@ -183,12 +183,18 @@
F.getTreeFactory());
// Iterate over the block-expr bindings.
- for (Environment::iterator I = Env.begin(), E = Env.end();
- I != E; ++I) {
+ for (Environment::iterator I = Env.begin(), E = Env.end(); I != E; ++I) {
const EnvironmentEntry &BlkExpr = I.getKey();
const SVal &X = I.getData();
- if (SymReaper.isLive(BlkExpr.getStmt(), BlkExpr.getLocationContext())) {
+ const bool IsBlkExprLive =
+ SymReaper.isLive(BlkExpr.getStmt(), BlkExpr.getLocationContext());
+
+ assert((isa<Expr>(BlkExpr.getStmt()) || !IsBlkExprLive) &&
+ "Only Exprs can be live, LivenessAnalysis argues about the liveness "
+ "of *values*!");
+
+ if (IsBlkExprLive) {
// Copy the binding to the new map.
EBMapRef = EBMapRef.add(BlkExpr, X);
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
