Have ARMBaseRegisterInfo::getCallPreservedMask return the 'correct' mask for the GHC calling convention.

This is purely academic because GHC calls are always tail calls so the register mask will never be used; however, this change makes the code clearer and brings the ARM implementation of the GHC calling convention in line with the X86 implementation. Also, it might save someone else some time trying to figuring out what is happening...

llvm-svn: 185592

2 files changed, 13 insertions, 10 deletions

diff --git a/llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp b/llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp
index 6a9bfc34d22..9274baf1198 100644
--- a/llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp
+++ b/llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp
@@ -59,14 +59,19 @@ ARMBaseRegisterInfo::getCalleeSavedRegs(const MachineFunction *MF) const {
   }
  
   if (ghcCall)
-    return CSR_GHC_SaveList;
+    // GHC set of callee saved regs is empty as all those regs are
+    // used for passing STG regs around
+    return CSR_NoRegs_SaveList;
   else
     return (STI.isTargetIOS() && !STI.isAAPCS_ABI())
       ? CSR_iOS_SaveList : CSR_AAPCS_SaveList;
 }
 
 const uint32_t*
-ARMBaseRegisterInfo::getCallPreservedMask(CallingConv::ID) const {
+ARMBaseRegisterInfo::getCallPreservedMask(CallingConv::ID CC) const {
+  if (CC == CallingConv::GHC)
+    // This is academic becase all GHC calls are (supposed to be) tail calls
+    return CSR_NoRegs_RegMask;
   return (STI.isTargetIOS() && !STI.isAAPCS_ABI())
     ? CSR_iOS_RegMask : CSR_AAPCS_RegMask;
 }
@@ -77,14 +82,18 @@ ARMBaseRegisterInfo::getNoPreservedMask() const {
 }
 
 const uint32_t*
-ARMBaseRegisterInfo::getThisReturnPreservedMask(CallingConv::ID) const {
+ARMBaseRegisterInfo::getThisReturnPreservedMask(CallingConv::ID CC) const {
   // This should return a register mask that is the same as that returned by
   // getCallPreservedMask but that additionally preserves the register used for
   // the first i32 argument (which must also be the register used to return a
   // single i32 return value)
   //
   // In case that the calling convention does not use the same register for
-  // both, the function should return NULL (does not currently apply)
+  // both or otherwise does not want to enable this optimization, the function
+  // should return NULL
+  if (CC == CallingConv::GHC)
+    // This is academic becase all GHC calls are (supposed to be) tail calls
+    return NULL;
   return (STI.isTargetIOS() && !STI.isAAPCS_ABI())
     ? CSR_iOS_ThisReturn_RegMask : CSR_AAPCS_ThisReturn_RegMask;
 }
diff --git a/llvm/lib/Target/ARM/ARMCallingConv.td b/llvm/lib/Target/ARM/ARMCallingConv.td
index 8ff666ed284..89c52239892 100644
--- a/llvm/lib/Target/ARM/ARMCallingConv.td
+++ b/llvm/lib/Target/ARM/ARMCallingConv.td
@@ -208,9 +208,3 @@ def CSR_iOS : CalleeSavedRegs<(add LR, R7, R6, R5, R4, (sub CSR_AAPCS, R9))>;
 
 def CSR_iOS_ThisReturn : CalleeSavedRegs<(add LR, R7, R6, R5, R4,
                                           (sub CSR_AAPCS_ThisReturn, R9))>;
-
-// GHC set of callee saved regs is empty as all those regs are
-// used for passing STG regs around
-// add is a workaround for not being able to compile empty list:
-// def CSR_GHC : CalleeSavedRegs<()>;
-def CSR_GHC : CalleeSavedRegs<(add)>;