[PATCH] D128068: [analyzer] Do not emit redundant SymbolCasts

[Gabor Marton via Phabricator via cfe-commits]

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In RegionStore::getBinding we call `evalCast` unconditionally to align
the stored value's type to the one that is being queried. However, the
stored type might be the same, so we may end up having redundant
SymbolCasts emitted. The simplest solution is to check whether the `to`
and `from` type are the same in `makeNonLoc`. We can't just do that check
in `evalCast` because there are many additonal logic before we'd end up
in `makeNonLoc`.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D128068

Files:
  clang/lib/StaticAnalyzer/Core/SValBuilder.cpp
  clang/test/Analysis/symbolcast-floatingpoint.cpp


Index: clang/test/Analysis/symbolcast-floatingpoint.cpp
===================================================================
--- /dev/null
+++ clang/test/Analysis/symbolcast-floatingpoint.cpp
@@ -0,0 +1,24 @@
+// RUN: %clang_analyze_cc1 -x c++ -analyzer-checker=debug.ExprInspection \
+// RUN:    -analyzer-config support-symbolic-integer-casts=false \
+// RUN:    -verify %s
+
+// RUN: %clang_analyze_cc1 -x c++ -analyzer-checker=debug.ExprInspection \
+// RUN:    -analyzer-config support-symbolic-integer-casts=true \
+// RUN:    -verify %s
+
+template <typename T>
+void clang_analyzer_dump(T);
+
+void test_no_redundant_floating_point_cast(int n) {
+
+  double D = n / 30;
+  clang_analyzer_dump(D); // expected-warning{{(double) ((reg_$0<int n>) / 30)}}
+
+  // There are two cast operations evaluated above:
+  // 1. (n / 30) is cast to a double during the store of `D`.
+  // 2. Then in the next line, in RegionStore::getBinding during the load of `D`.
+  //
+  // We should not see in the dump of the SVal any redundant casts like
+  // (double) ((double) $n / 30)
+
+}
Index: clang/lib/StaticAnalyzer/Core/SValBuilder.cpp
===================================================================
--- clang/lib/StaticAnalyzer/Core/SValBuilder.cpp
+++ clang/lib/StaticAnalyzer/Core/SValBuilder.cpp
@@ -113,6 +113,8 @@
                                           QualType fromTy, QualType toTy) {
   assert(operand);
   assert(!Loc::isLocType(toTy));
+  if (fromTy == toTy)
+    return operand;
   return nonloc::SymbolVal(SymMgr.getCastSymbol(operand, fromTy, toTy));
 }
 


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