[OpenMP] Update target directive codegen to use 4.5 implicit data mappings.
Summary:
This patch implements the 4.5 specification for the implicit data maps. OpenMP 4.5 specification changes the default way data is captured into a target region. All the non-aggregate kinds are passed by value by default. This required activating the capturing by value during SEMA for the target region. All the non-aggregate values that can be encoded in the size of a pointer are properly casted and forwarded to the runtime library. On top of fixing the previous weird behavior for mapping pointers in nested data regions (an explicit map was always required), this also improves performance as the number of allocations/transactions to the device per non-aggregate map are reduced from two to only one - instead of passing a reference and the value, only the value passed.
Explicit maps will be added later on once firstprivate, private, and map clauses' SEMA and parsing are available.
Reviewers: hfinkel, rjmccall, ABataev
Subscribers: cfe-commits, carlo.bertolli
Differential Revision: http://reviews.llvm.org/D14940
llvm-svn: 254521
diff --git a/clang/lib/Sema/SemaOpenMP.cpp b/clang/lib/Sema/SemaOpenMP.cpp
index 3972ff1..a458969 100644
--- a/clang/lib/Sema/SemaOpenMP.cpp
+++ b/clang/lib/Sema/SemaOpenMP.cpp
@@ -222,6 +222,8 @@
return Stack[Stack.size() - 2].Directive;
return OMPD_unknown;
}
+ /// \brief Return the directive associated with the provided scope.
+ OpenMPDirectiveKind getDirectiveForScope(const Scope *S) const;
/// \brief Set default data sharing attribute to none.
void setDefaultDSANone(SourceLocation Loc) {
@@ -729,12 +731,107 @@
return false;
}
+OpenMPDirectiveKind DSAStackTy::getDirectiveForScope(const Scope *S) const {
+ for (auto I = Stack.rbegin(), EE = Stack.rend(); I != EE; ++I)
+ if (I->CurScope == S)
+ return I->Directive;
+ return OMPD_unknown;
+}
+
void Sema::InitDataSharingAttributesStack() {
VarDataSharingAttributesStack = new DSAStackTy(*this);
}
#define DSAStack static_cast<DSAStackTy *>(VarDataSharingAttributesStack)
+bool Sema::IsOpenMPCapturedByRef(VarDecl *VD,
+ const CapturedRegionScopeInfo *RSI) {
+ assert(LangOpts.OpenMP && "OpenMP is not allowed");
+
+ auto &Ctx = getASTContext();
+ bool IsByRef = true;
+
+ // Find the directive that is associated with the provided scope.
+ auto DKind = DSAStack->getDirectiveForScope(RSI->TheScope);
+ auto Ty = VD->getType();
+
+ if (isOpenMPTargetDirective(DKind)) {
+ // This table summarizes how a given variable should be passed to the device
+ // given its type and the clauses where it appears. This table is based on
+ // the description in OpenMP 4.5 [2.10.4, target Construct] and
+ // OpenMP 4.5 [2.15.5, Data-mapping Attribute Rules and Clauses].
+ //
+ // =========================================================================
+ // | type | defaultmap | pvt | first | is_device_ptr | map | res. |
+ // | |(tofrom:scalar)| | pvt | | | |
+ // =========================================================================
+ // | scl | | | | - | | bycopy|
+ // | scl | | - | x | - | - | bycopy|
+ // | scl | | x | - | - | - | null |
+ // | scl | x | | | - | | byref |
+ // | scl | x | - | x | - | - | bycopy|
+ // | scl | x | x | - | - | - | null |
+ // | scl | | - | - | - | x | byref |
+ // | scl | x | - | - | - | x | byref |
+ //
+ // | agg | n.a. | | | - | | byref |
+ // | agg | n.a. | - | x | - | - | byref |
+ // | agg | n.a. | x | - | - | - | null |
+ // | agg | n.a. | - | - | - | x | byref |
+ // | agg | n.a. | - | - | - | x[] | byref |
+ //
+ // | ptr | n.a. | | | - | | bycopy|
+ // | ptr | n.a. | - | x | - | - | bycopy|
+ // | ptr | n.a. | x | - | - | - | null |
+ // | ptr | n.a. | - | - | - | x | byref |
+ // | ptr | n.a. | - | - | - | x[] | bycopy|
+ // | ptr | n.a. | - | - | x | | bycopy|
+ // | ptr | n.a. | - | - | x | x | bycopy|
+ // | ptr | n.a. | - | - | x | x[] | bycopy|
+ // =========================================================================
+ // Legend:
+ // scl - scalar
+ // ptr - pointer
+ // agg - aggregate
+ // x - applies
+ // - - invalid in this combination
+ // [] - mapped with an array section
+ // byref - should be mapped by reference
+ // byval - should be mapped by value
+ // null - initialize a local variable to null on the device
+ //
+ // Observations:
+ // - All scalar declarations that show up in a map clause have to be passed
+ // by reference, because they may have been mapped in the enclosing data
+ // environment.
+ // - If the scalar value does not fit the size of uintptr, it has to be
+ // passed by reference, regardless the result in the table above.
+ // - For pointers mapped by value that have either an implicit map or an
+ // array section, the runtime library may pass the NULL value to the
+ // device instead of the value passed to it by the compiler.
+
+ // FIXME: Right now, only implicit maps are implemented. Properly mapping
+ // values requires having the map, private, and firstprivate clauses SEMA
+ // and parsing in place, which we don't yet.
+
+ if (Ty->isReferenceType())
+ Ty = Ty->castAs<ReferenceType>()->getPointeeType();
+ IsByRef = !Ty->isScalarType();
+ }
+
+ // When passing data by value, we need to make sure it fits the uintptr size
+ // and alignment, because the runtime library only deals with uintptr types.
+ // If it does not fit the uintptr size, we need to pass the data by reference
+ // instead.
+ if (!IsByRef &&
+ (Ctx.getTypeSizeInChars(Ty) >
+ Ctx.getTypeSizeInChars(Ctx.getUIntPtrType()) ||
+ Ctx.getDeclAlign(VD) > Ctx.getTypeAlignInChars(Ctx.getUIntPtrType())))
+ IsByRef = true;
+
+ return IsByRef;
+}
+
bool Sema::IsOpenMPCapturedVar(VarDecl *VD) {
assert(LangOpts.OpenMP && "OpenMP is not allowed");
VD = VD->getCanonicalDecl();
@@ -5015,7 +5112,13 @@
if (!AStmt)
return StmtError();
- assert(isa<CapturedStmt>(AStmt) && "Captured statement expected");
+ CapturedStmt *CS = cast<CapturedStmt>(AStmt);
+ // 1.2.2 OpenMP Language Terminology
+ // Structured block - An executable statement with a single entry at the
+ // top and a single exit at the bottom.
+ // The point of exit cannot be a branch out of the structured block.
+ // longjmp() and throw() must not violate the entry/exit criteria.
+ CS->getCapturedDecl()->setNothrow();
// OpenMP [2.16, Nesting of Regions]
// If specified, a teams construct must be contained within a target