[PATCH] D25596: alpha.core.Conversion - Fix false positive for 'U32 += S16; ' expression, that is not unsafe

[Daniel Marjamäki via Phabricator via cfe-commits]

danielmarjamaki updated this revision to Diff 92634.
danielmarjamaki added a comment.

I added more testcases. There are several undetected "TODO: loss of precision" 
right now in the tests that I would like to fix. If this patch to fix FP is 
accepted I will commit it and continue working on the TODO tests. If it's not 
accepted I will continue investigating the TODO tests anyway..


Repository:
  rL LLVM

https://reviews.llvm.org/D25596

Files:
  lib/StaticAnalyzer/Checkers/ConversionChecker.cpp
  test/Analysis/conversion.c


Index: test/Analysis/conversion.c
===================================================================
--- test/Analysis/conversion.c
+++ test/Analysis/conversion.c
@@ -14,6 +14,64 @@
     S8 = U;
 }
 
+void addAssign() {
+  unsigned long L = 1000;
+  int I = -100;
+  U8 += L; // TODO: Loss of precision
+  L += I;
+}
+
+void subAssign() {
+  unsigned long L = 1000;
+  int I = -100;
+  U8 -= L; // TODO: Loss of precision
+  L -= I;
+}
+
+void mulAssign() {
+  unsigned long L = 1000;
+  int I = -1;
+  U8 *= L; // TODO: Loss of precision
+  L *= I;  // expected-warning {{Loss of sign in implicit conversion}}
+  I = 10;
+  L *= I;
+}
+
+void divAssign() {
+  unsigned long L = 1000;
+  int I = -1;
+  U8 /= L;
+  L /= I; // expected-warning {{Loss of sign in implicit conversion}}
+}
+
+void remAssign() {
+  unsigned long L = 1000;
+  int I = -1;
+  U8 %= L;
+  L %= I; // expected-warning {{Loss of sign in implicit conversion}}
+}
+
+void andAssign() {
+  unsigned long L = 1000;
+  int I = -1;
+  U8 &= L;
+  L &= I; // expected-warning {{Loss of sign in implicit conversion}}
+}
+
+void orAssign() {
+  unsigned long L = 1000;
+  int I = -1;
+  U8 |= L; // TODO: Loss of precision
+  L |= I;  // expected-warning {{Loss of sign in implicit conversion}}
+}
+
+void xorAssign() {
+  unsigned long L = 1000;
+  int I = -1;
+  U8 ^= L; // TODO: Loss of precision
+  L ^= I;  // expected-warning {{Loss of sign in implicit conversion}}
+}
+
 void init1() {
   long long A = 1LL << 60;
   short X = A; // expected-warning {{Loss of precision in implicit conversion}}
Index: lib/StaticAnalyzer/Checkers/ConversionChecker.cpp
===================================================================
--- lib/StaticAnalyzer/Checkers/ConversionChecker.cpp
+++ lib/StaticAnalyzer/Checkers/ConversionChecker.cpp
@@ -73,8 +73,22 @@
   // Loss of sign/precision in binary operation.
   if (const auto *B = dyn_cast<BinaryOperator>(Parent)) {
     BinaryOperator::Opcode Opc = B->getOpcode();
-    if (Opc == BO_Assign || Opc == BO_AddAssign || Opc == BO_SubAssign ||
-        Opc == BO_MulAssign) {
+    if (Opc == BO_Assign) {
+      LossOfSign = isLossOfSign(Cast, C);
+      LossOfPrecision = isLossOfPrecision(Cast, C);
+    } else if (Opc == BO_AddAssign || Opc == BO_SubAssign) {
+      // No loss of sign.
+      LossOfPrecision = isLossOfPrecision(Cast, C);
+    } else if (Opc == BO_MulAssign) {
+      LossOfSign = isLossOfSign(Cast, C);
+      LossOfPrecision = isLossOfPrecision(Cast, C);
+    } else if (Opc == BO_DivAssign || Opc == BO_RemAssign) {
+      LossOfSign = isLossOfSign(Cast, C);
+      // No loss of precision.
+    } else if (Opc == BO_AndAssign) {
+      LossOfSign = isLossOfSign(Cast, C);
+      // No loss of precision.
+    } else if (Opc == BO_OrAssign || Opc == BO_XorAssign) {
       LossOfSign = isLossOfSign(Cast, C);
       LossOfPrecision = isLossOfPrecision(Cast, C);
     } else if (B->isRelationalOp() || B->isMultiplicativeOp()) {
@@ -153,7 +167,7 @@
 }
 
 bool ConversionChecker::isLossOfPrecision(const ImplicitCastExpr *Cast,
-                                        CheckerContext &C) const {
+                                          CheckerContext &C) const {
   // Don't warn about explicit loss of precision.
   if (Cast->isEvaluatable(C.getASTContext()))
     return false;

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