Add a -ftrapv-handler= option which allows a handler to invoke instead of simply aborting when a signed operation overflows. This mirrors the (GCC-incompatible) behaviour from clang 1.0 and 1.1 when -ftrapv was specified, but allows the handler to be defined for each compilation unit.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@114192 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 60 insertions, 7 deletions

diff --git a/lib/CodeGen/CGExprScalar.cpp b/lib/CodeGen/CGExprScalar.cpp
index 68e0ff9497..bacb5641a7 100644
--- a/lib/CodeGen/CGExprScalar.cpp
+++ b/lib/CodeGen/CGExprScalar.cpp
@@ -1627,18 +1627,56 @@ Value *ScalarExprEmitter::EmitOverflowCheckedBinOp(const BinOpInfo &Ops) {
   Value *overflow = Builder.CreateExtractValue(resultAndOverflow, 1);
 
   // Branch in case of overflow.
+  llvm::BasicBlock *initialBB = Builder.GetInsertBlock();
   llvm::BasicBlock *overflowBB = CGF.createBasicBlock("overflow", CGF.CurFn);
   llvm::BasicBlock *continueBB = CGF.createBasicBlock("nooverflow", CGF.CurFn);
 
   Builder.CreateCondBr(overflow, overflowBB, continueBB);
 
   // Handle overflow with llvm.trap.
-  // TODO: it would be better to generate one of these blocks per function.
-  EmitOverflowBB(overflowBB);
-  
-  // Continue on.
+  const std::string *handlerName = 
+    &CGF.getContext().getLangOptions().OverflowHandler;
+  if (handlerName->empty()) {
+    EmitOverflowBB(overflowBB);
+    Builder.SetInsertPoint(continueBB);
+    return result;
+  }
+
+  // If an overflow handler is set, then we want to call it and then use its
+  // result, if it returns.
+  Builder.SetInsertPoint(overflowBB);
+
+  // Get the overflow handler.
+  const llvm::Type *Int8Ty = llvm::Type::getInt8Ty(VMContext);
+  std::vector<const llvm::Type*> argTypes;
+  argTypes.push_back(CGF.Int64Ty); argTypes.push_back(CGF.Int64Ty);
+  argTypes.push_back(Int8Ty); argTypes.push_back(Int8Ty);
+  llvm::FunctionType *handlerTy =
+      llvm::FunctionType::get(CGF.Int64Ty, argTypes, true);
+  llvm::Value *handler = CGF.CGM.CreateRuntimeFunction(handlerTy, *handlerName);
+
+  // Sign extend the args to 64-bit, so that we can use the same handler for
+  // all types of overflow.
+  llvm::Value *lhs = Builder.CreateSExt(Ops.LHS, CGF.Int64Ty);
+  llvm::Value *rhs = Builder.CreateSExt(Ops.RHS, CGF.Int64Ty);
+
+  // Call the handler with the two arguments, the operation, and the size of
+  // the result.
+  llvm::Value *handlerResult = Builder.CreateCall4(handler, lhs, rhs,
+      Builder.getInt8(OpID),
+      Builder.getInt8(cast<llvm::IntegerType>(opTy)->getBitWidth()));
+
+  // Truncate the result back to the desired size.
+  handlerResult = Builder.CreateTrunc(handlerResult, opTy);
+  Builder.CreateBr(continueBB);
+
   Builder.SetInsertPoint(continueBB);
-  return result;
+  llvm::PHINode *phi = Builder.CreatePHI(opTy);
+  phi->reserveOperandSpace(2);
+  phi->addIncoming(result, initialBB);
+  phi->addIncoming(handlerResult, overflowBB);
+
+  return phi;
 }
 
 Value *ScalarExprEmitter::EmitAdd(const BinOpInfo &Ops) {
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 1e1af35478..028db8ca02 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -1178,6 +1178,12 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   Args.AddLastArg(CmdArgs, options::OPT_fdiagnostics_parseable_fixits);
   Args.AddLastArg(CmdArgs, options::OPT_ftime_report);
   Args.AddLastArg(CmdArgs, options::OPT_ftrapv);
+
+  if (Arg *A = Args.getLastArg(options::OPT_ftrapv_handler_EQ)) {
+    CmdArgs.push_back("-ftrapv-handler");
+    CmdArgs.push_back(A->getValue(Args));
+  }
+
   Args.AddLastArg(CmdArgs, options::OPT_fwrapv);
   Args.AddLastArg(CmdArgs, options::OPT_fwritable_strings);
   Args.AddLastArg(CmdArgs, options::OPT_funroll_loops);
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 64ac3bad8c..d793fc01be 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -581,7 +581,12 @@ static void LangOptsToArgs(const LangOptions &Opts,
   switch (Opts.getSignedOverflowBehavior()) {
   case LangOptions::SOB_Undefined: break;
   case LangOptions::SOB_Defined:   Res.push_back("-fwrapv"); break;
-  case LangOptions::SOB_Trapping:  Res.push_back("-ftrapv"); break;
+  case LangOptions::SOB_Trapping:  
+    Res.push_back("-ftrapv"); break;
+    if (!Opts.OverflowHandler.empty()) {
+      Res.push_back("-ftrapv-handler");
+      Res.push_back(Opts.OverflowHandler);
+    }
   }
   if (Opts.HeinousExtensions)
     Res.push_back("-fheinous-gnu-extensions");
@@ -1312,8 +1317,12 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
   if (Args.hasArg(OPT_fvisibility_inlines_hidden))
     Opts.InlineVisibilityHidden = 1;
   
-  if (Args.hasArg(OPT_ftrapv))
+  if (Args.hasArg(OPT_ftrapv)) {
     Opts.setSignedOverflowBehavior(LangOptions::SOB_Trapping); 
+    // Set the handler, if one is specified.
+    Opts.OverflowHandler =
+        Args.getLastArgValue(OPT_ftrapv_handler);
+  }
   else if (Args.hasArg(OPT_fwrapv))
     Opts.setSignedOverflowBehavior(LangOptions::SOB_Defined);