[mips] Interrupt attribute support for mips32r2+.

Summary:
This patch adds support for using the "interrupt" attribute on Mips
for interrupt handling functions. At this time only mips32r2+ with the
o32 ABI with the static relocation model is supported. Unsupported
configurations will be rejected

Patch by Simon Dardis (+ clang-format & some trivial changes to follow the
LLVM coding standards by me).

Reviewers: mpf, dsanders

Subscribers: dsanders, vkalintiris, llvm-commits

Differential Revision: http://reviews.llvm.org/D10768

llvm-svn: 251286

1 files changed, 10 insertions, 0 deletions

diff --git a/llvm/lib/Target/Mips/MipsRegisterInfo.cpp b/llvm/lib/Target/Mips/MipsRegisterInfo.cpp
index 775d8006fdf..28e5a425849 100644
--- a/llvm/lib/Target/Mips/MipsRegisterInfo.cpp
+++ b/llvm/lib/Target/Mips/MipsRegisterInfo.cpp
@@ -84,6 +84,16 @@ MipsRegisterInfo::getRegPressureLimit(const TargetRegisterClass *RC,
 const MCPhysReg *
 MipsRegisterInfo::getCalleeSavedRegs(const MachineFunction *MF) const {
   const MipsSubtarget &Subtarget = MF->getSubtarget<MipsSubtarget>();
+  const Function *F = MF->getFunction();
+  if (F->hasFnAttribute("interrupt")) {
+    if (Subtarget.hasMips64())
+      return Subtarget.hasMips64r6() ? CSR_Interrupt_64R6_SaveList
+                                     : CSR_Interrupt_64_SaveList;
+    else
+      return Subtarget.hasMips32r6() ? CSR_Interrupt_32R6_SaveList
+                                     : CSR_Interrupt_32_SaveList;
+  }
+
   if (Subtarget.isSingleFloat())
     return CSR_SingleFloatOnly_SaveList;