Mercurial > projects > ldc
comparison gen/functions.cpp @ 1117:4c20fcc4252b
Fun with parameter attributes: For several of the "synthetic" parameters added
to D functions, we can apply noalias and nocapture. They are sret parameters,
'nest' pointers passed to nested functions, and _argptr:
Nocapture:
- Sret and nest are nocapture because they don't represent D-level variables,
and thus the callee can't (validly) obtain a pointer to them, let alone keep
it around after it returns.
- _argptr is nocapture because although the callee has access to it as a
pointer, that pointer is invalidated when it returns.
All three are noalias because they're function-local variables
- Sret and _argptr are noalias because they're freshly alloca'd memory only
used for a single function call that's not allowed to keep an aliasing
pointer to it around (since the parameter is nocapture).
- 'Nest' is noalias because the callee only ever has access to one such pointer
per parent function, and every parent function has a different one.
This commit also ensures attributes set on sret, _arguments and _argptr are
propagated to calls to such functions.
It also adds one exception to the general rule that attributes on function types
should propagate to calls: the type of a delegate's function pointer has a
'nest' parameter, but this can either be a true 'nest' (for delegates to nested
functions) or a 'this' (for delegates to member functions). Since 'this' is
neither noalias nor nocapture, and there's generally no way to tell which one it
is, we remove these attributes at the call site if the callee is a delegate.
author | Frits van Bommel <fvbommel wxs.nl> |
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date | Sat, 14 Mar 2009 22:15:31 +0100 |
parents | 802d508f66f1 |
children | 3d1b16dabd25 |
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1116:d584cda84b00 | 1117:4c20fcc4252b |
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20 #include "gen/todebug.h" | 20 #include "gen/todebug.h" |
21 #include "gen/classes.h" | 21 #include "gen/classes.h" |
22 #include "gen/dvalue.h" | 22 #include "gen/dvalue.h" |
23 #include "gen/abi.h" | 23 #include "gen/abi.h" |
24 | 24 |
25 using namespace llvm::Attribute; | |
26 | |
25 const llvm::FunctionType* DtoFunctionType(Type* type, Type* thistype, Type* nesttype, bool ismain) | 27 const llvm::FunctionType* DtoFunctionType(Type* type, Type* thistype, Type* nesttype, bool ismain) |
26 { | 28 { |
27 if (Logger::enabled()) | 29 if (Logger::enabled()) |
28 Logger::println("DtoFunctionType(%s)", type->toChars()); | 30 Logger::println("DtoFunctionType(%s)", type->toChars()); |
29 LOG_SCOPE | 31 LOG_SCOPE |
60 unsigned a = 0; | 62 unsigned a = 0; |
61 // sret return | 63 // sret return |
62 if (f->linkage != LINKintrinsic) | 64 if (f->linkage != LINKintrinsic) |
63 if (gABI->returnInArg(f)) | 65 if (gABI->returnInArg(f)) |
64 { | 66 { |
65 f->fty.arg_sret = new IrFuncTyArg(rt, true, llvm::Attribute::StructRet); | 67 f->fty.arg_sret = new IrFuncTyArg(rt, true, StructRet | NoAlias | NoCapture); |
66 rt = Type::tvoid; | 68 rt = Type::tvoid; |
67 lidx++; | 69 lidx++; |
68 } | 70 } |
69 // sext/zext return | 71 // sext/zext return |
70 else if (unsigned se = DtoShouldExtend(rt)) | 72 else if (unsigned se = DtoShouldExtend(rt)) |
84 } | 86 } |
85 | 87 |
86 // and nested functions | 88 // and nested functions |
87 else if (nesttype) | 89 else if (nesttype) |
88 { | 90 { |
89 f->fty.arg_nest = new IrFuncTyArg(nesttype, false); | 91 f->fty.arg_nest = new IrFuncTyArg(nesttype, false, NoAlias | NoCapture); |
90 lidx++; | 92 lidx++; |
91 } | 93 } |
92 | 94 |
93 // vararg functions are special too | 95 // vararg functions are special too |
94 if (f->varargs) | 96 if (f->varargs) |
101 { | 103 { |
102 // _arguments | 104 // _arguments |
103 f->fty.arg_arguments = new IrFuncTyArg(Type::typeinfo->type->arrayOf(), false); | 105 f->fty.arg_arguments = new IrFuncTyArg(Type::typeinfo->type->arrayOf(), false); |
104 lidx++; | 106 lidx++; |
105 // _argptr | 107 // _argptr |
106 f->fty.arg_argptr = new IrFuncTyArg(Type::tvoid->pointerTo(), false); | 108 f->fty.arg_argptr = new IrFuncTyArg(Type::tvoid->pointerTo(), false, NoAlias | NoCapture); |
107 lidx++; | 109 lidx++; |
108 } | 110 } |
109 } | 111 } |
110 else if (f->linkage == LINKc) | 112 else if (f->linkage == LINKc) |
111 { | 113 { |