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/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index 9b552e1..4f6bb08 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -215,6 +215,15 @@
#undef CLANG_ATTR_IDENTIFIER_ARG_LIST
}
+/// Determine whether the given attribute has a variadic identifier argument.
+static bool attributeHasVariadicIdentifierArg(const IdentifierInfo &II) {
+#define CLANG_ATTR_VARIADIC_IDENTIFIER_ARG_LIST
+ return llvm::StringSwitch<bool>(normalizeAttrName(II.getName()))
+#include "clang/Parse/AttrParserStringSwitches.inc"
+ .Default(false);
+#undef CLANG_ATTR_VARIADIC_IDENTIFIER_ARG_LIST
+}
+
/// Determine whether the given attribute parses a type argument.
static bool attributeIsTypeArgAttr(const IdentifierInfo &II) {
#define CLANG_ATTR_TYPE_ARG_LIST
@@ -282,7 +291,8 @@
ArgsVector ArgExprs;
if (Tok.is(tok::identifier)) {
// If this attribute wants an 'identifier' argument, make it so.
- bool IsIdentifierArg = attributeHasIdentifierArg(*AttrName);
+ bool IsIdentifierArg = attributeHasIdentifierArg(*AttrName) ||
+ attributeHasVariadicIdentifierArg(*AttrName);
ParsedAttr::Kind AttrKind =
ParsedAttr::getKind(AttrName, ScopeName, Syntax);
@@ -305,19 +315,25 @@
// Parse the non-empty comma-separated list of expressions.
do {
- bool Uneval = attributeParsedArgsUnevaluated(*AttrName);
- EnterExpressionEvaluationContext Unevaluated(
- Actions,
- Uneval ? Sema::ExpressionEvaluationContext::Unevaluated
- : Sema::ExpressionEvaluationContext::ConstantEvaluated);
+ ExprResult ArgExpr;
+ if (Tok.is(tok::identifier) &&
+ attributeHasVariadicIdentifierArg(*AttrName)) {
+ ArgExprs.push_back(ParseIdentifierLoc());
+ } else {
+ bool Uneval = attributeParsedArgsUnevaluated(*AttrName);
+ EnterExpressionEvaluationContext Unevaluated(
+ Actions,
+ Uneval ? Sema::ExpressionEvaluationContext::Unevaluated
+ : Sema::ExpressionEvaluationContext::ConstantEvaluated);
- ExprResult ArgExpr(
- Actions.CorrectDelayedTyposInExpr(ParseAssignmentExpression()));
- if (ArgExpr.isInvalid()) {
- SkipUntil(tok::r_paren, StopAtSemi);
- return 0;
+ ExprResult ArgExpr(
+ Actions.CorrectDelayedTyposInExpr(ParseAssignmentExpression()));
+ if (ArgExpr.isInvalid()) {
+ SkipUntil(tok::r_paren, StopAtSemi);
+ return 0;
+ }
+ ArgExprs.push_back(ArgExpr.get());
}
- ArgExprs.push_back(ArgExpr.get());
// Eat the comma, move to the next argument
} while (TryConsumeToken(tok::comma));
}