Override TRI::getSubClassWithSubReg for X86.

There are fewer registers with sub_8bit sub-registers in 32-bit mode
than in 64-bit mode.  In 32-bit mode, sub_8bit behaves the same as
sub_8bit_hi.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@141206 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 15 insertions, 0 deletions

diff --git a/lib/Target/X86/X86RegisterInfo.cpp b/lib/Target/X86/X86RegisterInfo.cpp
index 70402f3..23242e3 100644
--- a/lib/Target/X86/X86RegisterInfo.cpp
+++ b/lib/Target/X86/X86RegisterInfo.cpp
@@ -112,6 +112,18 @@ X86RegisterInfo::getSEHRegNum(unsigned i) const {
 }
 
 const TargetRegisterClass *
+X86RegisterInfo::getSubClassWithSubReg(const TargetRegisterClass *RC,
+                                       unsigned Idx) const {
+  // The sub_8bit sub-register index is more constrained in 32-bit mode.
+  // It behaves just like the sub_8bit_hi index.
+  if (!Is64Bit && Idx == X86::sub_8bit)
+    Idx = X86::sub_8bit_hi;
+
+  // Forward to TableGen's default version.
+  return X86GenRegisterInfo::getSubClassWithSubReg(RC, Idx);
+}
+
+const TargetRegisterClass *
 X86RegisterInfo::getMatchingSuperRegClass(const TargetRegisterClass *A,
                                           const TargetRegisterClass *B,
                                           unsigned SubIdx) const {
diff --git a/lib/Target/X86/X86RegisterInfo.h b/lib/Target/X86/X86RegisterInfo.h
index f293814..7d39c68 100644
--- a/lib/Target/X86/X86RegisterInfo.h
+++ b/lib/Target/X86/X86RegisterInfo.h
@@ -74,6 +74,9 @@ public:
   getMatchingSuperRegClass(const TargetRegisterClass *A,
                            const TargetRegisterClass *B, unsigned Idx) const;
 
+  virtual const TargetRegisterClass *
+  getSubClassWithSubReg(const TargetRegisterClass *RC, unsigned Idx) const;
+
   const TargetRegisterClass*
   getLargestLegalSuperClass(const TargetRegisterClass *RC) const;