Add begin_apply, abort_apply, and end_apply instructions to allow

yield_once coroutines to be executed.

Author: rjmccall

docs/SIL.rst

@@ -604,7 +604,10 @@ Currently, a coroutine may not have normal results.
 
 Coroutine functions may be used in many of the same ways as normal
 function values.  However, they cannot be called with the standard
-``apply`` or ``try_apply`` instructions.
+``apply`` or ``try_apply`` instructions.  A non-throwing yield-once
+coroutine can be called with the ``begin_apply`` instruction.  There
+is no support yet for calling a throwing yield-once coroutine or for
+calling a yield-many coroutine of any kind.
 
 Coroutines may contain the special ``yield`` and ``unwind`` instructions.
 
@@ -3137,6 +3140,102 @@ If the callee is generic, all of its generic parameters must be bound by the
 given substitution list. The arguments and return value is
 given with these generic substitutions applied.
 
+begin_apply
+```````````
+::
+
+  sil-instruction ::= 'begin_apply' '[nothrow]'? sil-value
+                        sil-apply-substitution-list?
+                        '(' (sil-value (',' sil-value)*)? ')'
+                        ':' sil-type
+
+  (%anyAddr, %float, %token) = begin_apply %0() : $@yield_once () -> (@yields @inout %Any, @yields Float)
+  // %anyAddr : $*Any
+  // %float : $Float
+  // %token is a token
+
+Transfers control to coroutine ``%0``, passing it the given arguments.
+The rules for the application generally follow the rules for ``apply``,
+except:
+
+- the callee value must have a ``yield_once`` coroutine type,
+
+- control returns to this function not when the coroutine performs a
+  ``return``, but when it performs a ``yield`, and
+
+- the instruction results are derived from the yields of the coroutine
+  instead of its normal results.
+
+The final result of a ``begin_apply`` is a "token", a special value which
+can only be used as the operand of an ``end_apply`` or ``abort_apply``
+instruction.  Before this second instruction is executed, the coroutine
+is said to be "suspended", and the token represents a reference to its
+suspended activation record.
+
+The other results of the instruction correspond to the yields in the
+coroutine type.  In general, the rules of a yield are similar to the rules
+for a parameter, interpreted as if the coroutine caller (the one
+executing the ``begin_apply``) were being "called" by the ``yield``:
+
+- If a yield has an indirect convention, the corresponding result will
+  have an address type; otherwise it has an object type.  For example,
+  a result corresponding to an ``@in Any`` yield will have type ``$Any``.
+
+- The convention attributes are the same as the parameter convention
+  attributes, interpreted as if the ``yield`` were the "call" and the
+  ``begin_apply`` marked the entry to the "callee".  For example,
+  an ``@in Any`` yield transferrs ownership of the ``Any`` value
+  reference from the coroutine to the caller, which must destroy
+  or move the value from that position before ending or aborting the
+  coroutine.
+
+A ``begin_apply`` must be uniquely either ended or aborted before
+exiting the function or looping to an earlier portion of the function.
+
+When throwing coroutines are supported, there will need to be a
+``try_begin_apply`` instruction.
+
+abort_apply
+```````````
+::
+
+  sil-instruction ::= 'abort_apply' sil-value
+
+  abort_apply %token
+
+Aborts the given coroutine activation, which is currently suspended at
+a ``yield`` instruction.  Transfers control to the coroutine and takes
+the ``unwind`` path from the ``yield``.  Control is transferred back
+when the coroutine reaches an ``unwind`` instruction.
+
+The operand must always be the token result of a ``begin_apply``
+instruction, which is why it need not specify a type.
+
+Throwing coroutines will not require a new instruction for aborting
+a coroutine; a coroutine is not allowed to throw when it is being aborted.
+
+end_apply
+`````````
+::
+
+  sil-instruction ::= 'end_apply' sil-value
+
+  end_apply %token
+
+Ends the given coroutine activation, which is currently suspended at
+a ``yield`` instruction.  Transfers control to the coroutine and takes
+the ``resume`` path from the ``yield``.  Control is transferred back
+when the coroutine reaches a ``return`` instruction.
+
+The operand must always be the token result of a ``begin_apply``
+instruction, which is why it need not specify a type.
+
+``end_apply`` currently has no instruction results.  If coroutines were
+allowed to have normal results, they would be producted by ``end_apply``.
+
+When throwing coroutines are supported, there will need to be a
+``try_end_apply`` instruction.
+
 partial_apply
 `````````````
 ::

include/swift/SIL/SILBuilder.h

@@ -381,6 +381,25 @@ class SILBuilder {
                                            SpecializationInfo));
   }
 
+  BeginApplyInst *createBeginApply(
+      SILLocation Loc, SILValue Fn, SubstitutionList Subs,
+      ArrayRef<SILValue> Args, bool isNonThrowing,
+      const GenericSpecializationInformation *SpecializationInfo = nullptr) {
+    return insert(BeginApplyInst::create(getSILDebugLocation(Loc), Fn, Subs,
+                                         Args, isNonThrowing, silConv, *F,
+                                         OpenedArchetypes, SpecializationInfo));
+  }
+
+  AbortApplyInst *createAbortApply(SILLocation loc, SILValue beginApply) {
+    return insert(new (getModule()) AbortApplyInst(getSILDebugLocation(loc),
+                                                   beginApply));
+  }
+
+  EndApplyInst *createEndApply(SILLocation loc, SILValue beginApply) {
+    return insert(new (getModule()) EndApplyInst(getSILDebugLocation(loc),
+                                                 beginApply));
+  }
+
   BuiltinInst *createBuiltin(SILLocation Loc, Identifier Name, SILType ResultTy,
                              SubstitutionList Subs,
                              ArrayRef<SILValue> Args) {

include/swift/SIL/SILCloner.h

@@ -614,6 +614,39 @@ SILCloner<ImplClass>::visitPartialApplyInst(PartialApplyInst *Inst) {
                                                              getBuilder())));
 }
 
+template<typename ImplClass>
+void
+SILCloner<ImplClass>::visitBeginApplyInst(BeginApplyInst *Inst) {
+  auto Args = getOpValueArray<8>(Inst->getArguments());
+  getBuilder().setCurrentDebugScope(getOpScope(Inst->getDebugScope()));
+  doPostProcess(Inst,
+    getBuilder().createBeginApply(getOpLocation(Inst->getLoc()),
+                                  getOpValue(Inst->getCallee()),
+                                  getOpSubstitutions(Inst->getSubstitutions()),
+                                  Args,
+                                  Inst->isNonThrowing(),
+                                  GenericSpecializationInformation::create(
+                                    Inst, getBuilder())));
+}
+
+template<typename ImplClass>
+void
+SILCloner<ImplClass>::visitAbortApplyInst(AbortApplyInst *Inst) {
+  getBuilder().setCurrentDebugScope(getOpScope(Inst->getDebugScope()));
+  doPostProcess(Inst,
+    getBuilder().createAbortApply(getOpLocation(Inst->getLoc()),
+                                  getOpValue(Inst->getOperand())));
+}
+
+template<typename ImplClass>
+void
+SILCloner<ImplClass>::visitEndApplyInst(EndApplyInst *Inst) {
+  getBuilder().setCurrentDebugScope(getOpScope(Inst->getDebugScope()));
+  doPostProcess(Inst,
+    getBuilder().createEndApply(getOpLocation(Inst->getLoc()),
+                                getOpValue(Inst->getOperand())));
+}
+
 template<typename ImplClass>
 void
 SILCloner<ImplClass>::visitFunctionRefInst(FunctionRefInst *Inst) {