[llvm-commits] [PATCH] __builtin_debugtrap() intrinsic function (change to Clang and CodeGen)

[Shuxin Yang]

Hi,

    This patch is to fix radar://8426430. It is about llvm support of 
__builtin_debugtrap()
which is supposed to consistently raise SIGTRAP across all systems. In 
contrast,
__builtin_trap() behave differently on different systems. e.g. it raises 
SIGTRAP on ARM, and
SIGILL on X86. The purpose of __builtin_debugtrap() is to consistently 
provide "trap"
functionality, in the mean time preserve the compatibility with on gcc 
on __builtin_trap().

   The X86 backend is already able to handle debugtrap(). This patch is to:
   1) make front-end recognize "__builtin_debugtrap()" (emboddied in the 
one-line change to Clang).
   2) In DAG legalization phase, by default, "debugtrap" will be 
replaced with "trap", which
      make the __builtin_debugtrap() "available" to all existing ports 
without the hassle of
      changing their code.
   3) If trap-function is specified (via -trap-func=xyz to llc), both 
__builtin_debugtrap() and
      __builtin_trap() will be expanded into the function call of the 
specified trap function.
     This behavior may need change in the future.

   The provided testing-case is to make sure 2) and 3) are working for 
ARM port, and we
already have a testing case for x86.

   This change pass regression test, SingleSource and MultipleSource test.

Thanks
Shuxin

-------------- next part --------------
Index: include/clang/Basic/Builtins.def
===================================================================
--- include/clang/Basic/Builtins.def	(revision 166287)
+++ include/clang/Basic/Builtins.def	(working copy)
@@ -479,6 +479,7 @@
 BUILTIN(__builtin_prefetch, "vvC*.", "nc")
 BUILTIN(__builtin_readcyclecounter, "ULLi", "n")
 BUILTIN(__builtin_trap, "v", "nr")
+BUILTIN(__builtin_debugtrap, "v", "nr")
 BUILTIN(__builtin_unreachable, "v", "nr")
 BUILTIN(__builtin_shufflevector, "v."   , "nc")
 BUILTIN(__builtin_alloca, "v*z"   , "n")
-------------- next part --------------
Index: test/CodeGen/ARM/trap.ll
===================================================================
--- test/CodeGen/ARM/trap.ll	(revision 166287)
+++ test/CodeGen/ARM/trap.ll	(working copy)
@@ -14,4 +14,16 @@
   unreachable
 }
 
+define void @t2() nounwind {
+entry:
+; INSTR: t2:
+; INSTR: trap
+
+; FUNC: t2:
+; FUNC: bl __trap
+  call void @llvm.debugtrap()
+  unreachable
+}
+
 declare void @llvm.trap() nounwind
+declare void @llvm.debugtrap() nounwind
Index: include/llvm/Intrinsics.td
===================================================================
--- include/llvm/Intrinsics.td	(revision 166287)
+++ include/llvm/Intrinsics.td	(working copy)
@@ -420,7 +420,7 @@
                      GCCBuiltin<"__builtin_flt_rounds">;
 def int_trap : Intrinsic<[], [], [IntrNoReturn]>,
                GCCBuiltin<"__builtin_trap">;
-def int_debugtrap : Intrinsic<[]>,
+def int_debugtrap : Intrinsic<[], [], [IntrNoReturn]>,
                     GCCBuiltin<"__builtin_debugtrap">;
 
 // NOP: calls/invokes to this intrinsic are removed by codegen
Index: lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- lib/Target/X86/X86ISelLowering.cpp	(revision 166287)
+++ lib/Target/X86/X86ISelLowering.cpp	(working copy)
@@ -557,6 +557,7 @@
   setOperationAction(ISD::ADJUST_TRAMPOLINE, MVT::Other, Custom);
 
   setOperationAction(ISD::TRAP, MVT::Other, Legal);
+  setOperationAction(ISD::DEBUGTRAP, MVT::Other, Legal);
 
   // VASTART needs to be custom lowered to use the VarArgsFrameIndex
   setOperationAction(ISD::VASTART           , MVT::Other, Custom);
Index: lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/LegalizeDAG.cpp	(revision 166287)
+++ lib/CodeGen/SelectionDAG/LegalizeDAG.cpp	(working copy)
@@ -1240,6 +1240,19 @@
     if (Action == TargetLowering::Legal)
       Action = TargetLowering::Custom;
     break;
+  case ISD::DEBUGTRAP:
+    Action = TLI.getOperationAction(Node->getOpcode(), Node->getValueType(0));
+    if (Action == TargetLowering::Expand) {
+      // replace ISD::DEBUGTRAP with ISD::TRAP
+      SDValue NewVal;
+      NewVal = DAG.getNode (ISD::TRAP, Node->getDebugLoc(), Node->getVTList(),
+                            Node->getOperand(0));
+      ReplaceNode(Node, NewVal.getNode());
+      LegalizeOp(NewVal.getNode());
+      return;
+    }
+    break;
+
   default:
     if (Node->getOpcode() >= ISD::BUILTIN_OP_END) {
       Action = TargetLowering::Legal;
Index: lib/CodeGen/SelectionDAG/TargetLowering.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/TargetLowering.cpp	(revision 166287)
+++ lib/CodeGen/SelectionDAG/TargetLowering.cpp	(working copy)
@@ -583,6 +583,11 @@
   // Default ISD::TRAP to expand (which turns it into abort).
   setOperationAction(ISD::TRAP, MVT::Other, Expand);
 
+  // On most systems, DEBUGTRAP and TRAP have no difference. The "Expand"
+  // here is to inform DAG Legalizer to replace DEBUGTRAP with TRAP.
+  //
+  setOperationAction(ISD::DEBUGTRAP, MVT::Other, Expand);
+
   IsLittleEndian = TD->isLittleEndian();
   PointerTy = MVT::getIntegerVT(8*TD->getPointerSize(0));
   memset(RegClassForVT, 0,MVT::LAST_VALUETYPE*sizeof(TargetRegisterClass*));
Index: lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp	(revision 166287)
+++ lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp	(working copy)
@@ -5175,10 +5175,13 @@
     return 0;
   }
 
+  case Intrinsic::debugtrap:
   case Intrinsic::trap: {
     StringRef TrapFuncName = TM.Options.getTrapFunctionName();
     if (TrapFuncName.empty()) {
-      DAG.setRoot(DAG.getNode(ISD::TRAP, dl,MVT::Other, getRoot()));
+      ISD::NodeType Op = (Intrinsic == Intrinsic::trap) ? 
+        ISD::TRAP : ISD::DEBUGTRAP;
+      DAG.setRoot(DAG.getNode(Op, dl,MVT::Other, getRoot()));
       return 0;
     }
     TargetLowering::ArgListTy Args;
@@ -5193,10 +5196,7 @@
     DAG.setRoot(Result.second);
     return 0;
   }
-  case Intrinsic::debugtrap: {
-    DAG.setRoot(DAG.getNode(ISD::DEBUGTRAP, dl,MVT::Other, getRoot()));
-    return 0;
-  }
+
   case Intrinsic::uadd_with_overflow:
   case Intrinsic::sadd_with_overflow:
   case Intrinsic::usub_with_overflow: