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Added atomicExchange to core.atomic #2729

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Aug 12, 2019
Merged

Added atomicExchange to core.atomic #2729

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16048f1
Added atomicExchange to core.atomic
TurkeyMan Aug 12, 2019
7e9c9db
Fix?
TurkeyMan Aug 12, 2019
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3 changes: 3 additions & 0 deletions changelog/atomic_exchange.dd
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Added `core.atomic.atomicExchange`.

Added missing `core.atomic.atomicExchange` function to the atomic suite.
185 changes: 185 additions & 0 deletions src/core/atomic.d
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Original file line number Diff line number Diff line change
Expand Up @@ -16,18 +16,21 @@ version (D_InlineAsm_X86)
{
version = AsmX86;
version = AsmX86_32;
enum has64BitXCHG = false;
enum has64BitCAS = true;
enum has128BitCAS = false;
}
else version (D_InlineAsm_X86_64)
{
version = AsmX86;
version = AsmX86_64;
enum has64BitXCHG = true;
enum has64BitCAS = true;
enum has128BitCAS = true;
}
else
{
enum has64BitXCHG = false;
enum has64BitCAS = false;
enum has128BitCAS = false;
}
Expand Down Expand Up @@ -189,6 +192,27 @@ version (CoreDdoc)
return TailShared!T.init;
}

/**
* Exchange `exchangeWith` with the memory referenced by `here`.
* This operation is both lock-free and atomic.
*
* Params:
* here = The address of the destination variable.
* exchangeWith = The value to exchange.
*
* Returns:
* The value held previously by `here`.
*/
shared(T) atomicExchange(MemoryOrder ms = MemoryOrder.seq,T,V)( shared(T)* here, V exchangeWith ) pure nothrow @nogc @safe
if ( !is(T == class) && !is(T U : U*) && __traits( compiles, { *here = exchangeWith; } ) );

/// Ditto
shared(T) atomicExchange(MemoryOrder ms = MemoryOrder.seq,T,V)( shared(T)* here, shared(V) exchangeWith ) pure nothrow @nogc @safe
if ( is(T == class) && __traits( compiles, { *here = exchangeWith; } ) );

/// Ditto
shared(T) atomicExchange(MemoryOrder ms = MemoryOrder.seq,T,V)( shared(T)* here, shared(V)* exchangeWith ) pure nothrow @nogc @safe
if ( is(T U : U*) && __traits( compiles, { *here = exchangeWith; } ) );

/**
* Stores 'writeThis' to the memory referenced by 'here' if the value
Expand Down Expand Up @@ -375,6 +399,68 @@ else version (AsmX86_32)
}
}

shared(T) atomicExchange(MemoryOrder ms = MemoryOrder.seq,T,V)( shared(T)* here, V exchangeWith ) pure nothrow @nogc @safe
if ( !is(T == class) && !is(T U : U*) && __traits( compiles, { *here = exchangeWith; } ) )
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@ibuclaw ibuclaw Aug 12, 2019

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Just to make sure you've done your homework, are there any invalid memory orders for this operation? (I think I know the answer without checking anyway).

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@TurkeyMan TurkeyMan Aug 12, 2019

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There are no invalid orders.
Infact, the order does not affect codegen in any way; it should be routed through to the backend to inform code mobility.

{
return atomicExchangeImpl(here, exchangeWith);
}

shared(T) atomicExchange(MemoryOrder ms = MemoryOrder.seq,T,V)( shared(T)* here, shared(V) exchangeWith ) pure nothrow @nogc @safe
if ( is(T == class) && __traits( compiles, { *here = exchangeWith; } ) )
{
return atomicExchangeImpl(here, exchangeWith);
}

shared(T) atomicExchange(MemoryOrder ms = MemoryOrder.seq,T,V)( shared(T)* here, shared(V)* exchangeWith ) pure nothrow @nogc @safe
if ( is(T U : U*) && __traits( compiles, { *here = exchangeWith; } ) )
{
return atomicExchangeImpl(here, exchangeWith);
}

private shared(T) atomicExchangeImpl(T,V)( shared(T)* here, V exchangeWith ) pure nothrow @nogc @safe
in ( atomicPtrIsProperlyAligned( here ), "Argument `here` is not properly aligned" )
{
static if ( T.sizeof == byte.sizeof )
{
asm pure nothrow @nogc @trusted
{
mov AL, exchangeWith;
mov ECX, here;
xchg [ECX], AL;
}
}
else static if ( T.sizeof == short.sizeof )
{
asm pure nothrow @nogc @trusted
{
mov AX, exchangeWith;
mov ECX, here;
xchg [ECX], AX;
}
}
else static if ( T.sizeof == int.sizeof )
{
asm pure nothrow @nogc @trusted
{
mov EAX, exchangeWith;
mov ECX, here;
xchg [ECX], EAX;
}
static if ( __traits(isFloating, T) )
{
asm pure nothrow @nogc @trusted
{
mov exchangeWith, EAX;
}
return exchangeWith;
}
}
else
{
static assert( false, "Invalid template type specified." );
}
}

bool casByRef(T,V1,V2)( ref T value, V1 ifThis, V2 writeThis ) pure nothrow @nogc @trusted
{
return cas(&value, ifThis, writeThis);
Expand Down Expand Up @@ -866,6 +952,85 @@ else version (AsmX86_64)
}
}

shared(T) atomicExchange(MemoryOrder ms = MemoryOrder.seq,T,V)( shared(T)* here, V exchangeWith ) pure nothrow @nogc @safe
if ( !is(T == class) && !is(T U : U*) && __traits( compiles, { *here = exchangeWith; } ) )
{
return atomicExchangeImpl(here, exchangeWith);
}

shared(T) atomicExchange(MemoryOrder ms = MemoryOrder.seq,T,V)( shared(T)* here, shared(V) exchangeWith ) pure nothrow @nogc @safe
if ( is(T == class) && __traits( compiles, { *here = exchangeWith; } ) )
{
return atomicExchangeImpl(here, exchangeWith);
}

shared(T) atomicExchange(MemoryOrder ms = MemoryOrder.seq,T,V)( shared(T)* here, shared(V)* exchangeWith ) pure nothrow @nogc @safe
if ( is(T U : U*) && __traits( compiles, { *here = exchangeWith; } ) )
{
return atomicExchangeImpl(here, exchangeWith);
}

private shared(T) atomicExchangeImpl(T,V)( shared(T)* here, V exchangeWith ) pure nothrow @nogc @safe
in ( atomicPtrIsProperlyAligned( here ), "Argument `here` is not properly aligned" )
do
{
static if ( T.sizeof == byte.sizeof )
{
asm pure nothrow @nogc @trusted
{
mov AL, exchangeWith;
mov RCX, here;
xchg [RCX], AL;
}
}
else static if ( T.sizeof == short.sizeof )
{
asm pure nothrow @nogc @trusted
{
mov AX, exchangeWith;
mov RCX, here;
xchg [RCX], AX;
}
}
else static if ( T.sizeof == int.sizeof )
{
asm pure nothrow @nogc @trusted
{
mov EAX, exchangeWith;
mov RCX, here;
xchg [RCX], EAX;
}
static if ( __traits(isFloating, T) )
{
asm pure nothrow @nogc @trusted
{
mov exchangeWith, EAX;
movss XMM0, exchangeWith;
}
}
}
else static if ( T.sizeof == long.sizeof )
{
asm pure nothrow @nogc @trusted
{
mov RAX, exchangeWith;
mov RCX, here;
xchg [RCX], RAX;
}
static if ( __traits(isFloating, T) )
{
asm pure nothrow @nogc @trusted
{
mov exchangeWith, RAX;
movsd XMM0, exchangeWith;
}
}
}
else
{
static assert( false, "Invalid template type specified." );
}
}

bool casByRef(T,V1,V2)( ref T value, V1 ifThis, V2 writeThis ) pure nothrow @nogc @trusted
{
Expand Down Expand Up @@ -1432,6 +1597,23 @@ if (__traits(isFloating, T))

version (unittest)
{
void testXCHG(T)( T val ) pure nothrow @nogc @trusted
in
{
assert(val !is T.init);
}
do
{
T base = cast(T)null;
shared(T) atom = cast(shared(T))null;

assert( base !is val, T.stringof );
assert( atom is base, T.stringof );

assert( atomicExchange( &atom, val ) is base, T.stringof );
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@thewilsonator thewilsonator Aug 12, 2019

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maybe do

auto x = atomicExchange( &atom, val );
static if (is(T == float))
    printf("%a, %a\n",x, base);
    assert(x is base, T.stringof);

and see what it thinks?

assert( atom is val, T.stringof );
}

void testCAS(T)( T val ) pure nothrow @nogc @trusted
in
{
Expand Down Expand Up @@ -1468,6 +1650,8 @@ version (unittest)

void testType(T)( T val = T.init + 1 ) pure nothrow @nogc @safe
{
static if ( T.sizeof < 8 || has64BitXCHG )
testXCHG!(T)( val );
testCAS!(T)( val );
testLoadStore!(MemoryOrder.seq, T)( val );
testLoadStore!(MemoryOrder.raw, T)( val );
Expand All @@ -1493,6 +1677,7 @@ version (unittest)
testType!(shared int*)();

static class Klass {}
testXCHG!(shared Klass)( new shared(Klass) );
testCAS!(shared Klass)( new shared(Klass) );

testType!(float)(1.0f);
Expand Down