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64c80b4e39
Summary:
Current generation of lifetime intrinsics does not handle cases like:
```
{
char x;
l1:
bar(&x, 1);
}
goto l1;
```
We will get code like this:
```
%x = alloca i8, align 1
call void @llvm.lifetime.start(i64 1, i8* nonnull %x)
br label %l1
l1:
%call = call i32 @bar(i8* nonnull %x, i32 1)
call void @llvm.lifetime.end(i64 1, i8* nonnull %x)
br label %l1
```
So the second time bar was called for x which is marked as dead.
Lifetime markers here are misleading so it's better to remove them at all.
This type of bypasses are rare, e.g. code detects just 8 functions building
clang (2329 targets).
PR28267
Reviewers: eugenis
Subscribers: beanz, mgorny, cfe-commits
Differential Revision: https://reviews.llvm.org/D24693
llvm-svn: 285176
71 lines
2.2 KiB
C++
71 lines
2.2 KiB
C++
//===--- VarBypassDetector.cpp - Bypass jumps detector ------------*- C++ -*-=//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file contains VarBypassDetector class, which is used to detect
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// local variable declarations which can be bypassed by jumps.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CLANG_LIB_CODEGEN_VARBYPASSDETECTOR_H
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#define LLVM_CLANG_LIB_CODEGEN_VARBYPASSDETECTOR_H
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/DenseSet.h"
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#include "llvm/ADT/SmallVector.h"
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namespace clang {
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class Decl;
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class Stmt;
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class VarDecl;
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namespace CodeGen {
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/// The class detects jumps which bypass local variables declaration:
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/// goto L;
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/// int a;
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/// L:
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///
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/// This is simplified version of JumpScopeChecker. Primary differences:
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/// * Detects only jumps into the scope local variables.
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/// * Does not detect jumps out of the scope of local variables.
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/// * Not limited to variables with initializers, JumpScopeChecker is limited.
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class VarBypassDetector {
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// Scope information. Contains a parent scope and related variable
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// declaration.
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llvm::SmallVector<std::pair<unsigned, const VarDecl *>, 48> Scopes;
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// List of jumps with scopes.
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llvm::SmallVector<std::pair<const Stmt *, unsigned>, 16> FromScopes;
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// Lookup map to find scope for destinations.
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llvm::DenseMap<const Stmt *, unsigned> ToScopes;
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// Set of variables which were bypassed by some jump.
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llvm::DenseSet<const VarDecl *> Bypasses;
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// If true assume that all variables are being bypassed.
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bool AlwaysBypassed = false;
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public:
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void Init(const Stmt *Body);
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/// Returns true if the variable declaration was by bypassed by any goto or
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/// switch statement.
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bool IsBypassed(const VarDecl *D) const {
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return AlwaysBypassed || Bypasses.find(D) != Bypasses.end();
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}
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private:
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bool BuildScopeInformation(const Decl *D, unsigned &ParentScope);
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bool BuildScopeInformation(const Stmt *S, unsigned &origParentScope);
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void Detect();
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void Detect(unsigned From, unsigned To);
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};
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}
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}
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#endif
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