[Hexagon] Use misaligned load instead of trap0(#0) for __builtin_trap

The trap instruction is intercepted by various runtime environments,
and instead of a crash it creates confusion.

This reapplies r354606 with a fix.

llvm-svn: 354611

llvm/lib/Target/Hexagon/HexagonInstrInfo.cpp

@@ -1313,6 +1313,38 @@ bool HexagonInstrInfo::expandPostRAPseudo(MachineInstr &MI) const {
       return true;
     }
 
+    case Hexagon::PS_crash: {
+      // Generate a misaligned load that is guaranteed to cause a crash.
+      class CrashPseudoSourceValue : public PseudoSourceValue {
+      public:
+        CrashPseudoSourceValue(const TargetInstrInfo &TII)
+          : PseudoSourceValue(TargetCustom, TII) {}
+
+        bool isConstant(const MachineFrameInfo *) const override {
+          return false;
+        }
+        bool isAliased(const MachineFrameInfo *) const override {
+          return false;
+        }
+        bool mayAlias(const MachineFrameInfo *) const override {
+          return false;
+        }
+        void printCustom(raw_ostream &OS) const override {
+          OS << "MisalignedCrash";
+        }
+      };
+
+      static const CrashPseudoSourceValue CrashPSV(*this);
+      MachineMemOperand *MMO = MF.getMachineMemOperand(
+          MachinePointerInfo(&CrashPSV),
+          MachineMemOperand::MOLoad | MachineMemOperand::MOVolatile, 8, 1);
+      BuildMI(MBB, MI, DL, get(Hexagon::PS_loadrdabs), Hexagon::D13)
+        .addImm(0xBADC0FEE)  // Misaligned load.
+        .addMemOperand(MMO);
+      MBB.erase(MI);
+      return true;
+    }
+
     case Hexagon::PS_tailcall_i:
       MI.setDesc(get(Hexagon::J2_jump));
       return true;

llvm/lib/Target/Hexagon/HexagonPatterns.td

@@ -3081,7 +3081,7 @@ def: Pat<(HexagonALLOCA I32:$Rs, (i32 imm:$A)),
 def HexagonBARRIER: SDNode<"HexagonISD::BARRIER", SDTNone, [SDNPHasChain]>;
 def: Pat<(HexagonBARRIER), (Y2_barrier)>;
 
-def: Pat<(trap), (J2_trap0 (i32 0))>;
+def: Pat<(trap), (PS_crash)>;
 
 // Read cycle counter.
 def SDTInt64Leaf: SDTypeProfile<1, 0, [SDTCisVT<0, i64>]>;

llvm/lib/Target/Hexagon/HexagonPseudo.td

@@ -559,3 +559,8 @@ defm PS_storerh : NewCircularStore<IntRegs, HalfWordAccess>;
 defm PS_storerf : NewCircularStore<IntRegs, HalfWordAccess>;
 defm PS_storeri : NewCircularStore<IntRegs, WordAccess>;
 defm PS_storerd : NewCircularStore<DoubleRegs, WordAccess>;
+
+// A pseudo that generates a runtime crash. This is used to implement
+// __builtin_trap.
+let hasSideEffects = 1, isPseudo = 1, isCodeGenOnly = 1, isSolo = 1 in
+def PS_crash: InstHexagon<(outs), (ins), "", [], "", PSEUDO, TypePSEUDO>;

llvm/test/CodeGen/Hexagon/trap-crash.ll

@@ -0,0 +1,20 @@
+; RUN: llc -march=hexagon < %s | FileCheck %s
+
+; Generate code that is guaranteed to crash. At the moment, it's a
+; misaligned load.
+; CHECK: memd(##3134984174)
+
+target triple = "hexagon"
+
+; Function Attrs: noreturn nounwind
+define i32 @f0() #0 {
+entry:
+  tail call void @llvm.trap()
+  unreachable
+}
+
+; Function Attrs: cold noreturn nounwind
+declare void @llvm.trap() #1
+
+attributes #0 = { noreturn nounwind "target-cpu"="hexagonv60" }
+attributes #1 = { cold noreturn nounwind }

llvm/test/CodeGen/Hexagon/trap-unreachable.ll

@@ -1,5 +1,7 @@
 ; RUN: llc -march=hexagon -trap-unreachable < %s | FileCheck %s
-; CHECK: trap
+
+; Trap is implemented via a misaligned load.
+; CHECK: memd(##3134984174)
 
 define void @fred() #0 {
   unreachable