Implement cpu_dispatch/cpu_specific Multiversioning
As documented here: https://software.intel.com/en-us/node/682969 and
https://software.intel.com/en-us/node/523346. cpu_dispatch multiversioning
is an ICC feature that provides for function multiversioning.
This feature is implemented with two attributes: First, cpu_specific,
which specifies the individual function versions. Second, cpu_dispatch,
which specifies the location of the resolver function and the list of
resolvable functions.
This is valuable since it provides a mechanism where the resolver's TU
can be specified in one location, and the individual implementions
each in their own translation units.
The goal of this patch is to be source-compatible with ICC, so this
implementation diverges from the ICC implementation in a few ways:
1- Linux x86/64 only: This implementation uses ifuncs in order to
properly dispatch functions. This is is a valuable performance benefit
over the ICC implementation. A future patch will be provided to enable
this feature on Windows, but it will obviously more closely fit ICC's
implementation.
2- CPU Identification functions: ICC uses a set of custom functions to identify
the feature list of the host processor. This patch uses the cpu_supports
functionality in order to better align with 'target' multiversioning.
1- cpu_dispatch function def/decl: ICC's cpu_dispatch requires that the function
marked cpu_dispatch be an empty definition. This patch supports that as well,
however declarations are also permitted, since the linker will solve the
issue of multiple emissions.
Differential Revision: https://reviews.llvm.org/D47474
llvm-svn: 337552
diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
index f81a34c..d57473c 100644
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -1585,6 +1585,7 @@
}
bool Ambiguous = false;
+ bool IsMV = false;
if (Overloads) {
for (OverloadExpr::decls_iterator it = Overloads->decls_begin(),
@@ -1598,11 +1599,16 @@
if (const FunctionDecl *OverloadDecl
= dyn_cast<FunctionDecl>((*it)->getUnderlyingDecl())) {
if (OverloadDecl->getMinRequiredArguments() == 0) {
- if (!ZeroArgCallReturnTy.isNull() && !Ambiguous) {
+ if (!ZeroArgCallReturnTy.isNull() && !Ambiguous &&
+ (!IsMV || !(OverloadDecl->isCPUDispatchMultiVersion() ||
+ OverloadDecl->isCPUSpecificMultiVersion()))) {
ZeroArgCallReturnTy = QualType();
Ambiguous = true;
- } else
+ } else {
ZeroArgCallReturnTy = OverloadDecl->getReturnType();
+ IsMV = OverloadDecl->isCPUDispatchMultiVersion() ||
+ OverloadDecl->isCPUSpecificMultiVersion();
+ }
}
}
}
@@ -1683,7 +1689,7 @@
NamedDecl *Fn = (*It)->getUnderlyingDecl();
// Don't print overloads for non-default multiversioned functions.
if (const auto *FD = Fn->getAsFunction()) {
- if (FD->isMultiVersion() &&
+ if (FD->isMultiVersion() && FD->hasAttr<TargetAttr>() &&
!FD->getAttr<TargetAttr>()->isDefaultVersion())
continue;
}
@@ -1725,6 +1731,21 @@
!isa<CXXOperatorCallExpr>(E));
}
+static bool IsCPUDispatchCPUSpecificMultiVersion(const Expr *E) {
+ if (const auto *UO = dyn_cast<UnaryOperator>(E))
+ E = UO->getSubExpr();
+
+ if (const auto *ULE = dyn_cast<UnresolvedLookupExpr>(E)) {
+ if (ULE->getNumDecls() == 0)
+ return false;
+
+ const NamedDecl *ND = *ULE->decls_begin();
+ if (const auto *FD = dyn_cast<FunctionDecl>(ND))
+ return FD->isCPUDispatchMultiVersion() || FD->isCPUSpecificMultiVersion();
+ }
+ return false;
+}
+
bool Sema::tryToRecoverWithCall(ExprResult &E, const PartialDiagnostic &PD,
bool ForceComplain,
bool (*IsPlausibleResult)(QualType)) {
@@ -1741,12 +1762,13 @@
// so we can emit a fixit and carry on pretending that E was
// actually a CallExpr.
SourceLocation ParenInsertionLoc = getLocForEndOfToken(Range.getEnd());
- Diag(Loc, PD)
- << /*zero-arg*/ 1 << Range
- << (IsCallableWithAppend(E.get())
- ? FixItHint::CreateInsertion(ParenInsertionLoc, "()")
- : FixItHint());
- notePlausibleOverloads(*this, Loc, Overloads, IsPlausibleResult);
+ bool IsMV = IsCPUDispatchCPUSpecificMultiVersion(E.get());
+ Diag(Loc, PD) << /*zero-arg*/ 1 << IsMV << Range
+ << (IsCallableWithAppend(E.get())
+ ? FixItHint::CreateInsertion(ParenInsertionLoc, "()")
+ : FixItHint());
+ if (!IsMV)
+ notePlausibleOverloads(*this, Loc, Overloads, IsPlausibleResult);
// FIXME: Try this before emitting the fixit, and suppress diagnostics
// while doing so.
@@ -1757,8 +1779,10 @@
if (!ForceComplain) return false;
- Diag(Loc, PD) << /*not zero-arg*/ 0 << Range;
- notePlausibleOverloads(*this, Loc, Overloads, IsPlausibleResult);
+ bool IsMV = IsCPUDispatchCPUSpecificMultiVersion(E.get());
+ Diag(Loc, PD) << /*not zero-arg*/ 0 << IsMV << Range;
+ if (!IsMV)
+ notePlausibleOverloads(*this, Loc, Overloads, IsPlausibleResult);
E = ExprError();
return true;
}