Overhaul the TargetMachine and LLVMTargetMachine Classes (#111234)

Following discussions in #110443, and the following earlier discussions
in https://lists.llvm.org/pipermail/llvm-dev/2017-October/117907.html,
https://reviews.llvm.org/D38482, https://reviews.llvm.org/D38489, this
PR attempts to overhaul the `TargetMachine` and `LLVMTargetMachine`
interface classes. More specifically:
1. Makes `TargetMachine` the only class implemented under
`TargetMachine.h` in the `Target` library.
2. `TargetMachine` contains target-specific interface functions that
relate to IR/CodeGen/MC constructs, whereas before (at least on paper)
it was supposed to have only IR/MC constructs. Any Target that doesn't
want to use the independent code generator simply does not implement
them, and returns either `false` or `nullptr`.
3. Renames `LLVMTargetMachine` to `CodeGenCommonTMImpl`. This renaming
aims to make the purpose of `LLVMTargetMachine` clearer. Its interface
was moved under the CodeGen library, to further emphasis its usage in
Targets that use CodeGen directly.
4. Makes `TargetMachine` the only interface used across LLVM and its
projects. With these changes, `CodeGenCommonTMImpl` is simply a set of
shared function implementations of `TargetMachine`, and CodeGen users
don't need to static cast to `LLVMTargetMachine` every time they need a
CodeGen-specific feature of the `TargetMachine`.
5. More importantly, does not change any requirements regarding library
linking.

cc @arsenm @aeubanks

1 files changed, 4 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/MachineModuleInfo.cpp b/llvm/lib/CodeGen/MachineModuleInfo.cpp
index c664959..6167e99 100644
--- a/llvm/lib/CodeGen/MachineModuleInfo.cpp
+++ b/llvm/lib/CodeGen/MachineModuleInfo.cpp
@@ -48,7 +48,7 @@ MachineModuleInfo::MachineModuleInfo(MachineModuleInfo &&MMI)
   TheModule = MMI.TheModule;
 }
 
-MachineModuleInfo::MachineModuleInfo(const LLVMTargetMachine *TM)
+MachineModuleInfo::MachineModuleInfo(const TargetMachine *TM)
     : TM(*TM), Context(TM->getTargetTriple(), TM->getMCAsmInfo(),
                        TM->getMCRegisterInfo(), TM->getMCSubtargetInfo(),
                        nullptr, &TM->Options.MCOptions, false) {
@@ -56,7 +56,7 @@ MachineModuleInfo::MachineModuleInfo(const LLVMTargetMachine *TM)
   initialize();
 }
 
-MachineModuleInfo::MachineModuleInfo(const LLVMTargetMachine *TM,
+MachineModuleInfo::MachineModuleInfo(const TargetMachine *TM,
                                      MCContext *ExtContext)
     : TM(*TM), Context(TM->getTargetTriple(), TM->getMCAsmInfo(),
                        TM->getMCRegisterInfo(), TM->getMCSubtargetInfo(),
@@ -151,13 +151,13 @@ FunctionPass *llvm::createFreeMachineFunctionPass() {
 }
 
 MachineModuleInfoWrapperPass::MachineModuleInfoWrapperPass(
-    const LLVMTargetMachine *TM)
+    const TargetMachine *TM)
     : ImmutablePass(ID), MMI(TM) {
   initializeMachineModuleInfoWrapperPassPass(*PassRegistry::getPassRegistry());
 }
 
 MachineModuleInfoWrapperPass::MachineModuleInfoWrapperPass(
-    const LLVMTargetMachine *TM, MCContext *ExtContext)
+    const TargetMachine *TM, MCContext *ExtContext)
     : ImmutablePass(ID), MMI(TM, ExtContext) {
   initializeMachineModuleInfoWrapperPassPass(*PassRegistry::getPassRegistry());
 }