Begin adding docs and IR-level support for the inalloca attribute

The inalloca attribute is designed to support passing C++ objects by
value in the Microsoft C++ ABI.  It behaves the same as byval, except
that it always implies that the argument is in memory and that the bytes
are never copied.  This attribute allows the caller to take the address
of an outgoing argument's memory and execute arbitrary code to store
into it.

This patch adds basic IR support, docs, and verification.  It does not
attempt to implement any lowering or fix any possibly broken transforms.

When this patch lands, a complete description of this feature should
appear at http://llvm.org/docs/InAlloca.html .

Differential Revision: http://llvm-reviews.chandlerc.com/D2173

llvm-svn: 197645

3 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/AsmParser/LLLexer.cpp b/llvm/lib/AsmParser/LLLexer.cpp
index 3c384f5fcca..1b32047e4bf 100644
--- a/llvm/lib/AsmParser/LLLexer.cpp
+++ b/llvm/lib/AsmParser/LLLexer.cpp
@@ -572,6 +572,7 @@ lltok::Kind LLLexer::LexIdentifier() {
   KEYWORD(alwaysinline);
   KEYWORD(builtin);
   KEYWORD(byval);
+  KEYWORD(inalloca);
   KEYWORD(cold);
   KEYWORD(inlinehint);
   KEYWORD(inreg);
diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index 3b903cdb090..a5b2aa586e4 100644
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -944,6 +944,7 @@ bool LLParser::ParseFnAttributeValuePairs(AttrBuilder &B,
               "invalid use of attribute on a function");
       break;
     case lltok::kw_byval:
+    case lltok::kw_inalloca:
     case lltok::kw_nest:
     case lltok::kw_noalias:
     case lltok::kw_nocapture:
@@ -1156,6 +1157,7 @@ bool LLParser::ParseOptionalParamAttrs(AttrBuilder &B) {
       continue;
     }
     case lltok::kw_byval:           B.addAttribute(Attribute::ByVal); break;
+    case lltok::kw_inalloca:        B.addAttribute(Attribute::InAlloca); break;
     case lltok::kw_inreg:           B.addAttribute(Attribute::InReg); break;
     case lltok::kw_nest:            B.addAttribute(Attribute::Nest); break;
     case lltok::kw_noalias:         B.addAttribute(Attribute::NoAlias); break;
@@ -1218,6 +1220,7 @@ bool LLParser::ParseOptionalReturnAttrs(AttrBuilder &B) {
     // Error handling.
     case lltok::kw_align:
     case lltok::kw_byval:
+    case lltok::kw_inalloca:
     case lltok::kw_nest:
     case lltok::kw_nocapture:
     case lltok::kw_returned:
diff --git a/llvm/lib/AsmParser/LLToken.h b/llvm/lib/AsmParser/LLToken.h
index 786d84d7663..5a6866dd149 100644
--- a/llvm/lib/AsmParser/LLToken.h
+++ b/llvm/lib/AsmParser/LLToken.h
@@ -99,6 +99,7 @@ namespace lltok {
     kw_sanitize_address,
     kw_builtin,
     kw_byval,
+    kw_inalloca,
     kw_cold,
     kw_inlinehint,
     kw_inreg,