Add a CoveredBySubRegs property to Register descriptions.

When set, this bit indicates that a register is completely defined by
the value of its sub-registers.

Use the CoveredBySubRegs property to infer which super-registers are
call-preserved given a list of callee-saved registers.  For example, the
ARM registers D8-D15 are callee-saved.  This now automatically implies
that Q4-Q7 are call-preserved.

Conversely, Win64 callees save XMM6-XMM15, but the corresponding
YMM6-YMM15 registers are not call-preserved because they are not fully
defined by their sub-registers.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@148363 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 1 insertions, 0 deletions

diff --git a/utils/TableGen/CodeGenRegisters.h b/utils/TableGen/CodeGenRegisters.h
index 6153fe5179..0551055806 100644
--- a/utils/TableGen/CodeGenRegisters.h
+++ b/utils/TableGen/CodeGenRegisters.h
@@ -36,6 +36,7 @@ namespace llvm {
     Record *TheDef;
     unsigned EnumValue;
     unsigned CostPerUse;
+    bool CoveredBySubRegs;
 
     // Map SubRegIndex -> Register.
     typedef std::map<Record*, CodeGenRegister*, LessRecord> SubRegMap;