Add support for __builtin_os_log_format[_buffer_size]

These new builtins support a mechanism for logging OS events, using a
printf-like format string to specify the layout of data in a buffer.
The _buffer_size version of the builtin can be used to determine the size
of the buffer to allocate to hold the data, and then __builtin_os_log_format
can write data into that buffer. This implements format checking to report
mismatches between the format string and the data arguments. Most of this
code was written by Chris Willmore.

Differential Revision: https://reviews.llvm.org/D25888

llvm-svn: 284990

1 files changed, 84 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index a81a75b4135..92a4447398b 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -11,14 +11,15 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "CodeGenFunction.h"
 #include "CGCXXABI.h"
 #include "CGObjCRuntime.h"
 #include "CGOpenCLRuntime.h"
+#include "CodeGenFunction.h"
 #include "CodeGenModule.h"
 #include "TargetInfo.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Decl.h"
+#include "clang/Analysis/Analyses/OSLog.h"
 #include "clang/Basic/TargetBuiltins.h"
 #include "clang/Basic/TargetInfo.h"
 #include "clang/CodeGen/CGFunctionInfo.h"
@@ -564,6 +565,18 @@ Value *CodeGenFunction::EmitMSVCBuiltinExpr(MSVCIntrin BuiltinID,
   llvm_unreachable("Incorrect MSVC intrinsic!");
 }
 
+namespace {
+// ARC cleanup for __builtin_os_log_format
+struct CallObjCArcUse final : EHScopeStack::Cleanup {
+  CallObjCArcUse(llvm::Value *object) : object(object) {}
+  llvm::Value *object;
+
+  void Emit(CodeGenFunction &CGF, Flags flags) override {
+    CGF.EmitARCIntrinsicUse(object);
+  }
+};
+}
+
 RValue CodeGenFunction::EmitBuiltinExpr(const FunctionDecl *FD,
                                         unsigned BuiltinID, const CallExpr *E,
                                         ReturnValueSlot ReturnValue) {
@@ -2597,6 +2610,76 @@ RValue CodeGenFunction::EmitBuiltinExpr(const FunctionDecl *FD,
     // Fall through - it's already mapped to the intrinsic by GCCBuiltin.
     break;
   }
+  case Builtin::BI__builtin_os_log_format: {
+    assert(E->getNumArgs() >= 2 &&
+           "__builtin_os_log_format takes at least 2 arguments");
+    analyze_os_log::OSLogBufferLayout Layout;
+    analyze_os_log::computeOSLogBufferLayout(CGM.getContext(), E, Layout);
+    Address BufAddr = EmitPointerWithAlignment(E->getArg(0));
+    // Ignore argument 1, the format string. It is not currently used.
+    CharUnits Offset;
+    Builder.CreateStore(
+        Builder.getInt8(Layout.getSummaryByte()),
+        Builder.CreateConstByteGEP(BufAddr, Offset++, "summary"));
+    Builder.CreateStore(
+        Builder.getInt8(Layout.getNumArgsByte()),
+        Builder.CreateConstByteGEP(BufAddr, Offset++, "numArgs"));
+
+    llvm::SmallVector<llvm::Value *, 4> RetainableOperands;
+    for (const auto &Item : Layout.Items) {
+      Builder.CreateStore(
+          Builder.getInt8(Item.getDescriptorByte()),
+          Builder.CreateConstByteGEP(BufAddr, Offset++, "argDescriptor"));
+      Builder.CreateStore(
+          Builder.getInt8(Item.getSizeByte()),
+          Builder.CreateConstByteGEP(BufAddr, Offset++, "argSize"));
+      Address Addr = Builder.CreateConstByteGEP(BufAddr, Offset);
+      if (const Expr *TheExpr = Item.getExpr()) {
+        Addr = Builder.CreateElementBitCast(
+            Addr, ConvertTypeForMem(TheExpr->getType()));
+        // Check if this is a retainable type.
+        if (TheExpr->getType()->isObjCRetainableType()) {
+          assert(getEvaluationKind(TheExpr->getType()) == TEK_Scalar &&
+                 "Only scalar can be a ObjC retainable type");
+          llvm::Value *SV = EmitScalarExpr(TheExpr, /*Ignore*/ false);
+          RValue RV = RValue::get(SV);
+          LValue LV = MakeAddrLValue(Addr, TheExpr->getType());
+          EmitStoreThroughLValue(RV, LV);
+          // Check if the object is constant, if not, save it in
+          // RetainableOperands.
+          if (!isa<Constant>(SV))
+            RetainableOperands.push_back(SV);
+        } else {
+          EmitAnyExprToMem(TheExpr, Addr, Qualifiers(), /*isInit*/ true);
+        }
+      } else {
+        Addr = Builder.CreateElementBitCast(Addr, Int32Ty);
+        Builder.CreateStore(
+            Builder.getInt32(Item.getConstValue().getQuantity()), Addr);
+      }
+      Offset += Item.size();
+    }
+
+    // Push a clang.arc.use cleanup for each object in RetainableOperands. The
+    // cleanup will cause the use to appear after the final log call, keeping
+    // the object valid while it’s held in the log buffer.  Note that if there’s
+    // a release cleanup on the object, it will already be active; since
+    // cleanups are emitted in reverse order, the use will occur before the
+    // object is released.
+    if (!RetainableOperands.empty() && getLangOpts().ObjCAutoRefCount &&
+        CGM.getCodeGenOpts().OptimizationLevel != 0)
+      for (llvm::Value *object : RetainableOperands)
+        pushFullExprCleanup<CallObjCArcUse>(getARCCleanupKind(), object);
+
+    return RValue::get(BufAddr.getPointer());
+  }
+
+  case Builtin::BI__builtin_os_log_format_buffer_size: {
+    analyze_os_log::OSLogBufferLayout Layout;
+    analyze_os_log::computeOSLogBufferLayout(CGM.getContext(), E, Layout);
+    return RValue::get(ConstantInt::get(ConvertType(E->getType()),
+                                        Layout.size().getQuantity()));
+  }
   }
 
   // If this is an alias for a lib function (e.g. __builtin_sin), emit