Fixed X86 Interrupt handler calling convention for MCU target

[aaboud]

Summary

MCU target has its own ABI, however X86 interrupt handler calling convention overrides this ABI.
Fixed the ordering to check first for X86 interrupt handler then for MCU target.

Notice that not like other calling conventions, X86_INTR is valid also in MCU.

[nadav]

LGTM.

llvm/trunk/lib/Target/X86/X86CallingConv.td

 ]>;
 
 //===----------------------------------------------------------------------===//
 // X86 Root Argument Calling Conventions
 //===----------------------------------------------------------------------===//
 
 // This is the root argument convention for the X86-32 backend.
 def CC_X86_32 : CallingConv<[
+  // X86_INTR calling convention is valid in MCU target and should override the
+  // MCU calling convention. Thus, this should be checked before isTargetMCU().
+  CCIfCC<"CallingConv::X86_INTR", CCDelegateTo<CC_X86_32_Intr>>,
   CCIfSubtarget<"isTargetMCU()", CCDelegateTo<CC_X86_32_MCU>>,
   CCIfCC<"CallingConv::X86_FastCall", CCDelegateTo<CC_X86_32_FastCall>>,
   CCIfCC<"CallingConv::X86_VectorCall", CCDelegateTo<CC_X86_32_VectorCall>>,
   CCIfCC<"CallingConv::X86_ThisCall", CCDelegateTo<CC_X86_32_ThisCall>>,
   CCIfCC<"CallingConv::Fast", CCDelegateTo<CC_X86_32_FastCC>>,
   CCIfCC<"CallingConv::GHC", CCDelegateTo<CC_X86_32_GHC>>,
   CCIfCC<"CallingConv::HiPE", CCDelegateTo<CC_X86_32_HiPE>>,
-  CCIfCC<"CallingConv::X86_INTR", CCDelegateTo<CC_X86_32_Intr>>,
 
   // Otherwise, drop to normal X86-32 CC
   CCDelegateTo<CC_X86_32_C>
 ]>;
 
 // This is the root argument convention for the X86-64 backend.
 def CC_X86_64 : CallingConv<[
   CCIfCC<"CallingConv::GHC", CCDelegateTo<CC_X86_64_GHC>>,