Update the comments on default subtargets based on feedback.

llvm-svn: 309041

llvm/lib/Target/AArch64/AArch64TargetMachine.h

@@ -36,8 +36,9 @@ public:
 
   ~AArch64TargetMachine() override;
   const AArch64Subtarget *getSubtargetImpl(const Function &F) const override;
-  // The no argument getSubtargetImpl, while it exists on some, targets is
-  // deprecated and should not be used.
+  // DO NOT IMPLEMENT: There is no such thing as a valid default subtarget,
+  // subtargets are per-function entities based on the target-specific
+  // attributes of each function.
   const AArch64Subtarget *getSubtargetImpl() const = delete;
 
   // Pass Pipeline Configuration

llvm/lib/Target/ARM/ARMTargetMachine.h

@@ -47,8 +47,9 @@ public:
   ~ARMBaseTargetMachine() override;
 
   const ARMSubtarget *getSubtargetImpl(const Function &F) const override;
-  // The no argument getSubtargetImpl, while it exists on some targets, is
-  // deprecated and should not be used.
+  // DO NOT IMPLEMENT: There is no such thing as a valid default subtarget,
+  // subtargets are per-function entities based on the target-specific
+  // attributes of each function.
   const ARMSubtarget *getSubtargetImpl() const = delete;
   bool isLittleEndian() const { return isLittle; }
 

llvm/lib/Target/PowerPC/PPCTargetMachine.h

@@ -41,8 +41,9 @@ public:
   ~PPCTargetMachine() override;
 
   const PPCSubtarget *getSubtargetImpl(const Function &F) const override;
-  // The no argument getSubtargetImpl, while it exists on some targets, is
-  // deprecated and should not be used.
+  // DO NOT IMPLEMENT: There is no such thing as a valid default subtarget,
+  // subtargets are per-function entities based on the target-specific
+  // attributes of each function.
   const PPCSubtarget *getSubtargetImpl() const = delete;
 
   // Pass Pipeline Configuration

llvm/lib/Target/X86/X86TargetMachine.h

@@ -40,8 +40,9 @@ public:
   ~X86TargetMachine() override;
 
   const X86Subtarget *getSubtargetImpl(const Function &F) const override;
-  // The no argument getSubtargetImpl, while it exists on some targets, is
-  // deprecated and should not be used.
+  // DO NOT IMPLEMENT: There is no such thing as a valid default subtarget,
+  // subtargets are per-function entities based on the target-specific
+  // attributes of each function.
   const X86Subtarget *getSubtargetImpl() const = delete;
 
   TargetIRAnalysis getTargetIRAnalysis() override;