Author: Yitzhak Mandelbaum Date: 2022-04-04T12:20:43Z New Revision: 506ec85ba82a39748f8fb07c15b93e1e958a9611
URL: https://github.com/llvm/llvm-project/commit/506ec85ba82a39748f8fb07c15b93e1e958a9611 DIFF: https://github.com/llvm/llvm-project/commit/506ec85ba82a39748f8fb07c15b93e1e958a9611.diff LOG: [clang][dataflow] Add support for clang's `__builtin_expect`. This patch adds basic modeling of `__builtin_expect`, just to propagate the (first) argument, making the call transparent. Driveby: adds tests for proper handling of other builtins. Differential Revision: https://reviews.llvm.org/D122908 Added: Modified: clang/lib/Analysis/FlowSensitive/Transfer.cpp clang/unittests/Analysis/FlowSensitive/TransferTest.cpp Removed: ################################################################################ diff --git a/clang/lib/Analysis/FlowSensitive/Transfer.cpp b/clang/lib/Analysis/FlowSensitive/Transfer.cpp index 1f5de9d67c135..271167b90030d 100644 --- a/clang/lib/Analysis/FlowSensitive/Transfer.cpp +++ b/clang/lib/Analysis/FlowSensitive/Transfer.cpp @@ -22,6 +22,7 @@ #include "clang/AST/StmtVisitor.h" #include "clang/Analysis/FlowSensitive/DataflowEnvironment.h" #include "clang/Analysis/FlowSensitive/Value.h" +#include "clang/Basic/Builtins.h" #include "clang/Basic/OperatorKinds.h" #include "llvm/ADT/STLExtras.h" #include "llvm/Support/Casting.h" @@ -444,6 +445,9 @@ class TransferVisitor : public ConstStmtVisitor<TransferVisitor> { } void VisitCallExpr(const CallExpr *S) { + // Of clang's builtins, only `__builtin_expect` is handled explicitly, since + // others (like trap, debugtrap, and unreachable) are handled by CFG + // construction. if (S->isCallToStdMove()) { assert(S->getNumArgs() == 1); @@ -455,6 +459,18 @@ class TransferVisitor : public ConstStmtVisitor<TransferVisitor> { return; Env.setStorageLocation(*S, *ArgLoc); + } else if (S->getDirectCallee() != nullptr && + S->getDirectCallee()->getBuiltinID() == + Builtin::BI__builtin_expect) { + assert(S->getNumArgs() > 0); + assert(S->getArg(0) != nullptr); + // `__builtin_expect` returns by-value, so strip away any potential + // references in the argument. + auto *ArgLoc = Env.getStorageLocation( + *S->getArg(0)->IgnoreParenImpCasts(), SkipPast::Reference); + if (ArgLoc == nullptr) + return; + Env.setStorageLocation(*S, *ArgLoc); } } diff --git a/clang/unittests/Analysis/FlowSensitive/TransferTest.cpp b/clang/unittests/Analysis/FlowSensitive/TransferTest.cpp index 540ed4781aebf..2fa5be182eea5 100644 --- a/clang/unittests/Analysis/FlowSensitive/TransferTest.cpp +++ b/clang/unittests/Analysis/FlowSensitive/TransferTest.cpp @@ -2368,6 +2368,131 @@ TEST_F(TransferTest, AssignFromBoolNegation) { }); } +TEST_F(TransferTest, BuiltinExpect) { + std::string Code = R"( + void target(long Foo) { + long Bar = __builtin_expect(Foo, true); + /*[[p]]*/ + } + )"; + runDataflow(Code, + [](llvm::ArrayRef< + std::pair<std::string, DataflowAnalysisState<NoopLattice>>> + Results, + ASTContext &ASTCtx) { + ASSERT_THAT(Results, ElementsAre(Pair("p", _))); + const auto &Env = Results[0].second.Env; + + const ValueDecl *FooDecl = findValueDecl(ASTCtx, "Foo"); + ASSERT_THAT(FooDecl, NotNull()); + + const ValueDecl *BarDecl = findValueDecl(ASTCtx, "Bar"); + ASSERT_THAT(BarDecl, NotNull()); + + EXPECT_EQ(Env.getValue(*FooDecl, SkipPast::None), + Env.getValue(*BarDecl, SkipPast::None)); + }); +} + +TEST_F(TransferTest, BuiltinUnreachable) { + std::string Code = R"( + void target(bool Foo) { + bool Bar = false; + if (Foo) + Bar = Foo; + else + __builtin_unreachable(); + (void)0; + /*[[p]]*/ + } + )"; + runDataflow(Code, + [](llvm::ArrayRef< + std::pair<std::string, DataflowAnalysisState<NoopLattice>>> + Results, + ASTContext &ASTCtx) { + ASSERT_THAT(Results, ElementsAre(Pair("p", _))); + const auto &Env = Results[0].second.Env; + + const ValueDecl *FooDecl = findValueDecl(ASTCtx, "Foo"); + ASSERT_THAT(FooDecl, NotNull()); + + const ValueDecl *BarDecl = findValueDecl(ASTCtx, "Bar"); + ASSERT_THAT(BarDecl, NotNull()); + + // `__builtin_unreachable` promises that the code is + // unreachable, so the compiler treats the "then" branch as the + // only possible predecessor of this statement. + EXPECT_EQ(Env.getValue(*FooDecl, SkipPast::None), + Env.getValue(*BarDecl, SkipPast::None)); + }); +} + +TEST_F(TransferTest, BuiltinTrap) { + std::string Code = R"( + void target(bool Foo) { + bool Bar = false; + if (Foo) + Bar = Foo; + else + __builtin_trap(); + (void)0; + /*[[p]]*/ + } + )"; + runDataflow(Code, + [](llvm::ArrayRef< + std::pair<std::string, DataflowAnalysisState<NoopLattice>>> + Results, + ASTContext &ASTCtx) { + ASSERT_THAT(Results, ElementsAre(Pair("p", _))); + const auto &Env = Results[0].second.Env; + + const ValueDecl *FooDecl = findValueDecl(ASTCtx, "Foo"); + ASSERT_THAT(FooDecl, NotNull()); + + const ValueDecl *BarDecl = findValueDecl(ASTCtx, "Bar"); + ASSERT_THAT(BarDecl, NotNull()); + + // `__builtin_trap` ensures program termination, so only the + // "then" branch is a predecessor of this statement. + EXPECT_EQ(Env.getValue(*FooDecl, SkipPast::None), + Env.getValue(*BarDecl, SkipPast::None)); + }); +} + +TEST_F(TransferTest, BuiltinDebugTrap) { + std::string Code = R"( + void target(bool Foo) { + bool Bar = false; + if (Foo) + Bar = Foo; + else + __builtin_debugtrap(); + (void)0; + /*[[p]]*/ + } + )"; + runDataflow(Code, + [](llvm::ArrayRef< + std::pair<std::string, DataflowAnalysisState<NoopLattice>>> + Results, + ASTContext &ASTCtx) { + ASSERT_THAT(Results, ElementsAre(Pair("p", _))); + const auto &Env = Results[0].second.Env; + + const ValueDecl *FooDecl = findValueDecl(ASTCtx, "Foo"); + ASSERT_THAT(FooDecl, NotNull()); + + const ValueDecl *BarDecl = findValueDecl(ASTCtx, "Bar"); + ASSERT_THAT(BarDecl, NotNull()); + + // `__builtin_debugtrap` doesn't ensure program termination. + EXPECT_NE(Env.getValue(*FooDecl, SkipPast::None), + Env.getValue(*BarDecl, SkipPast::None)); + }); +} + TEST_F(TransferTest, StaticIntSingleVarDecl) { std::string Code = R"( void target() { _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
