[PATCH] Recognize _alloca as an alias for the alloca builtin

[Reid Kleckner]

This has the unfortunate side effect of suggesting _alloca as a
typo-correction for malloc when it is undeclared, but I don't see a good
way around that.

http://llvm-reviews.chandlerc.com/D1989

Files:
  include/clang/Basic/Builtins.def
  lib/CodeGen/CGBuiltin.cpp
  test/CodeGen/builtins.c
  test/SemaCXX/no-implicit-builtin-decls.cpp

Index: include/clang/Basic/Builtins.def
===================================================================
--- include/clang/Basic/Builtins.def
+++ include/clang/Basic/Builtins.def
@@ -671,6 +671,7 @@
 BUILTIN(__builtin_rindex, "c*cC*i", "Fn")
 
 // Microsoft builtins.
+BUILTIN(_alloca, "v*z", "n")
 BUILTIN(__assume, "vb", "n")
 BUILTIN(__noop, "v.", "n")
 BUILTIN(__debugbreak, "v", "n")
Index: lib/CodeGen/CGBuiltin.cpp
===================================================================
--- lib/CodeGen/CGBuiltin.cpp
+++ lib/CodeGen/CGBuiltin.cpp
@@ -603,6 +603,7 @@
   }
 
   case Builtin::BIalloca:
+  case Builtin::BI_alloca:
   case Builtin::BI__builtin_alloca: {
     Value *Size = EmitScalarExpr(E->getArg(0));
     return RValue::get(Builder.CreateAlloca(Builder.getInt8Ty(), Size));
Index: test/CodeGen/builtins.c
===================================================================
--- test/CodeGen/builtins.c
+++ test/CodeGen/builtins.c
@@ -210,3 +210,11 @@
   // CHECK: call i64 @llvm.readcyclecounter()
   return __builtin_readcyclecounter();
 }
+
+// CHECK-LABEL: define void @test_alloca
+void test_alloca(int n) {
+  extern void capture(void *);
+  capture(_alloca(n));
+  // CHECK: alloca i8, i64 %
+  // CHECK: call void @capture
+}
Index: test/SemaCXX/no-implicit-builtin-decls.cpp
===================================================================
--- test/SemaCXX/no-implicit-builtin-decls.cpp
+++ test/SemaCXX/no-implicit-builtin-decls.cpp
@@ -1,6 +1,6 @@
 // RUN: %clang_cc1 -fsyntax-only -verify %s
 
-void f() {
+void f() { // expected-note at +1 {{declared here}}
   void *p = malloc(sizeof(int) * 10); // expected-error{{use of undeclared identifier 'malloc'}}
 }
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