1 files changed, 40 insertions, 0 deletions
diff --git a/llvm/lib/Target/X86/X86CallingConv.cpp b/llvm/lib/Target/X86/X86CallingConv.cpp
index 7a58e9ae069..9be1147df3c 100644
--- a/llvm/lib/Target/X86/X86CallingConv.cpp
+++ b/llvm/lib/Target/X86/X86CallingConv.cpp
@@ -287,5 +287,45 @@ static bool CC_X86_32_MCUInReg(unsigned &ValNo, MVT &ValVT, MVT &LocVT,
   return true;
 }
 
+/// X86 interrupt handlers can only take one or two stack arguments, but if
+/// there are two arguments, they are in the opposite order from the standard
+/// convention. Therefore, we have to look at the argument count up front before
+/// allocating stack for each argument.
+static bool CC_X86_Intr(unsigned &ValNo, MVT &ValVT, MVT &LocVT,
+                        CCValAssign::LocInfo &LocInfo,
+                        ISD::ArgFlagsTy &ArgFlags, CCState &State) {
+  const MachineFunction &MF = State.getMachineFunction();
+  size_t ArgCount = State.getMachineFunction().getFunction().arg_size();
+  bool Is64Bit = static_cast<const X86Subtarget &>(MF.getSubtarget()).is64Bit();
+  unsigned SlotSize = Is64Bit ? 8 : 4;
+  unsigned Offset;
+  if (ArgCount == 1 && ValNo == 0) {
+    // If we have one argument, the argument is five stack slots big, at fixed
+    // offset zero.
+    Offset = State.AllocateStack(5 * SlotSize, 4);
+  } else if (ArgCount == 2 && ValNo == 0) {
+    // If we have two arguments, the stack slot is *after* the error code
+    // argument. Pretend it doesn't consume stack space, and account for it when
+    // we assign the second argument.
+    Offset = SlotSize;
+  } else if (ArgCount == 2 && ValNo == 1) {
+    // If this is the second of two arguments, it must be the error code. It
+    // appears first on the stack, and is then followed by the five slot
+    // interrupt struct.
+    Offset = 0;
+    (void)State.AllocateStack(6 * SlotSize, 4);
+  } else {
+    report_fatal_error("unsupported x86 interrupt prototype");
+  }
+
+  // FIXME: This should be accounted for in
+  // X86FrameLowering::getFrameIndexReference, not here.
+  if (Is64Bit && ArgCount == 2)
+    Offset += SlotSize;
+
+  State.addLoc(CCValAssign::getMem(ValNo, ValVT, Offset, LocVT, LocInfo));
+  return true;
+}
+
 // Provides entry points of CC_X86 and RetCC_X86.
 #include "X86GenCallingConv.inc"