When directly supported, this intrinsic will either return a call to
the appropriate cache clearing system call (usually ``__clear_cache``)
when the caches are not unified (ARM, Mips) or just remove the call
-altogether when they are (ex. x86_64).
-
-Targets must implement it directly to have either behaviour, as the
-default is to bail with "Not Implemented" message.
+altogether when they are (ex. x86_64). Some targets can lower these
+directly into special instructions, if they have it.
+
+The default behaviour is to emit a call to ``__clear_cache``, so in
+case a target doesn't support it, the user gets a linker error rather
+than a compiler internal error. It also provides a work around to
+the user (implement an empty function called ``__clear_cache``) while
+LLVM doesn't implement it in the target's back-end.
+
+Please note that the caller is responsible for ensuring the cache
+is actually cleared. This is most important in targets that don't
+need to flush the cache directly (ex. x86_64) and could potentially
+still execute old instructions while the cache is not cleared. LLVM
+will *not* insert nops or busy-wait sequences.
Standard C Library Intrinsics
-----------------------------
}
/// Return the builtin name for the __builtin___clear_cache intrinsic
+ /// Default is to invoke the clear cache library call
virtual const char * getClearCacheBuiltinName() const {
- llvm_unreachable("Not Implemented");
+ return "__clear_cache";
}
/// Return the type that should be used to zero or sign extend a
bool shouldConvertConstantLoadToIntImm(const APInt &Imm,
Type *Ty) const override;
- /// Clear cache library call
- const char * getClearCacheBuiltinName() const {
- return "__clear_cache";
- }
-
protected:
std::pair<const TargetRegisterClass*, uint8_t>
findRepresentativeClass(MVT VT) const override;
bool MemcpyStrSrc,
MachineFunction &MF) const;
- /// Clear cache library call
- const char * getClearCacheBuiltinName() const {
- return "__clear_cache";
- }
-
/// isFPImmLegal - Returns true if the target can instruction select the
/// specified FP immediate natively. If false, the legalizer will
/// materialize the FP immediate as a load from a constant pool.