/usr/include/llvm-3.9/llvm/CodeGen/AtomicExpandUtils.h is in llvm-3.9-dev 1:3.9.1-19ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 | //===-- AtomicExpandUtils.h - Utilities for expanding atomic instructions -===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/ADT/STLExtras.h"
#include "llvm/IR/IRBuilder.h"
namespace llvm {
class Value;
class AtomicRMWInst;
/// Parameters (see the expansion example below):
/// (the builder, %addr, %loaded, %new_val, ordering,
/// /* OUT */ %success, /* OUT */ %new_loaded)
typedef function_ref<void(IRBuilder<> &, Value *, Value *, Value *,
AtomicOrdering, Value *&, Value *&)> CreateCmpXchgInstFun;
/// \brief Expand an atomic RMW instruction into a loop utilizing
/// cmpxchg. You'll want to make sure your target machine likes cmpxchg
/// instructions in the first place and that there isn't another, better,
/// transformation available (for example AArch32/AArch64 have linked loads).
///
/// This is useful in passes which can't rewrite the more exotic RMW
/// instructions directly into a platform specific intrinsics (because, say,
/// those intrinsics don't exist). If such a pass is able to expand cmpxchg
/// instructions directly however, then, with this function, it could avoid two
/// extra module passes (avoiding passes by `-atomic-expand` and itself). A
/// specific example would be PNaCl's `RewriteAtomics` pass.
///
/// Given: atomicrmw some_op iN* %addr, iN %incr ordering
///
/// The standard expansion we produce is:
/// [...]
/// %init_loaded = load atomic iN* %addr
/// br label %loop
/// loop:
/// %loaded = phi iN [ %init_loaded, %entry ], [ %new_loaded, %loop ]
/// %new = some_op iN %loaded, %incr
/// ; This is what -atomic-expand will produce using this function on i686 targets:
/// %pair = cmpxchg iN* %addr, iN %loaded, iN %new_val
/// %new_loaded = extractvalue { iN, i1 } %pair, 0
/// %success = extractvalue { iN, i1 } %pair, 1
/// ; End callback produced IR
/// br i1 %success, label %atomicrmw.end, label %loop
/// atomicrmw.end:
/// [...]
///
/// Returns true if the containing function was modified.
bool
expandAtomicRMWToCmpXchg(AtomicRMWInst *AI, CreateCmpXchgInstFun Factory);
}
|