[PowerPC] Clean up generation of ha16() / lo16() markers

When targeting the Darwin assembler, we need to generate markers ha16() and
lo16() to designate the high and low parts of a (symbolic) immediate.  This
is necessary not just for plain symbols, but also for certain symbolic
expression, typically along the lines of ha16(A - B).  The latter doesn't
work when simply using VariantKind flags on the symbol reference.
This is why the current back-end uses hacks (explicitly called out as such
via multiple FIXMEs) in the symbolLo/symbolHi print methods.

This patch uses target-defined MCExpr codes to represent the Darwin
ha16/lo16 constructs, following along the lines of the equivalent solution
used by the ARM back end to handle their :upper16: / :lower16: markers.
This allows us to get rid of special handling both in the symbolLo/symbolHi
print method and in the common code MCExpr::print routine.  Instead, the
ha16 / lo16 markers are printed simply in a custom print routine for the
target MCExpr types.  (As a result, the symbolLo/symbolHi print methods
can now replaced by a single printS16ImmOperand routine that also handles
symbolic operands.)

The patch also provides a EvaluateAsRelocatableImpl routine to handle
ha16/lo16 constructs.  This is not actually used at the moment by any
in-tree code, but is provided as it makes merging into David Fang's
out-of-tree Mach-O object writer simpler.

Since there is no longer any need to treat VK_PPC_GAS_HA16 and
VK_PPC_DARWIN_HA16 differently, they are merged into a single
VK_PPC_ADDR16_HA (and likewise for the _LO16 types).



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182616 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/PowerPC/PPCAsmPrinter.cpp

@@ -20,6 +20,7 @@
 #include "PPC.h"
 #include "InstPrinter/PPCInstPrinter.h"
 #include "MCTargetDesc/PPCPredicates.h"
+#include "MCTargetDesc/PPCMCExpr.h"
 #include "PPCSubtarget.h"
 #include "PPCTargetMachine.h"
 #include "llvm/ADT/MapVector.h"
@@ -910,6 +911,9 @@ EmitFunctionStubs(const MachineModuleInfoMachO::SymbolListTy &Stubs) {
       OutStreamer.EmitSymbolAttribute(RawSym, MCSA_IndirectSymbol);
 
       const MCExpr *Anon = MCSymbolRefExpr::Create(AnonSymbol, OutContext);
+      const MCExpr *LazyPtrExpr = MCSymbolRefExpr::Create(LazyPtr, OutContext);
+      const MCExpr *Sub =
+        MCBinaryExpr::CreateSub(LazyPtrExpr, Anon, OutContext);
 
       // mflr r0
       OutStreamer.EmitInstruction(MCInstBuilder(PPC::MFLR).addReg(PPC::R0));
@@ -919,21 +923,20 @@ EmitFunctionStubs(const MachineModuleInfoMachO::SymbolListTy &Stubs) {
       // mflr r11
       OutStreamer.EmitInstruction(MCInstBuilder(PPC::MFLR).addReg(PPC::R11));
       // addis r11, r11, ha16(LazyPtr - AnonSymbol)
-      const MCExpr *Sub =
-        MCBinaryExpr::CreateSub(MCSymbolRefExpr::Create(LazyPtr, OutContext),
-                                Anon, OutContext);
+      const MCExpr *SubHa16 = PPCMCExpr::CreateHa16(Sub, OutContext);
       OutStreamer.EmitInstruction(MCInstBuilder(PPC::ADDIS)
         .addReg(PPC::R11)
         .addReg(PPC::R11)
-        .addExpr(Sub));
+        .addExpr(SubHa16));
       // mtlr r0
       OutStreamer.EmitInstruction(MCInstBuilder(PPC::MTLR).addReg(PPC::R0));
 
       // ldu r12, lo16(LazyPtr - AnonSymbol)(r11)
       // lwzu r12, lo16(LazyPtr - AnonSymbol)(r11)
+      const MCExpr *SubLo16 = PPCMCExpr::CreateLo16(Sub, OutContext);
       OutStreamer.EmitInstruction(MCInstBuilder(isPPC64 ? PPC::LDU : PPC::LWZU)
         .addReg(PPC::R12)
-        .addExpr(Sub).addExpr(Sub)
+        .addExpr(SubLo16).addExpr(SubLo16)
         .addReg(PPC::R11));
       // mtctr r12
       OutStreamer.EmitInstruction(MCInstBuilder(PPC::MTCTR).addReg(PPC::R12));
@@ -967,24 +970,22 @@ EmitFunctionStubs(const MachineModuleInfoMachO::SymbolListTy &Stubs) {
     MCSymbol *Stub = Stubs[i].first;
     MCSymbol *RawSym = Stubs[i].second.getPointer();
     MCSymbol *LazyPtr = GetLazyPtr(Stub, OutContext);
+    const MCExpr *LazyPtrExpr = MCSymbolRefExpr::Create(LazyPtr, OutContext);
 
     OutStreamer.SwitchSection(StubSection);
     EmitAlignment(4);
     OutStreamer.EmitLabel(Stub);
     OutStreamer.EmitSymbolAttribute(RawSym, MCSA_IndirectSymbol);
+
     // lis r11, ha16(LazyPtr)
-    const MCExpr *LazyPtrHa16 =
-      MCSymbolRefExpr::Create(LazyPtr, MCSymbolRefExpr::VK_PPC_DARWIN_HA16,
-                              OutContext);
+    const MCExpr *LazyPtrHa16 = PPCMCExpr::CreateHa16(LazyPtrExpr, OutContext);
     OutStreamer.EmitInstruction(MCInstBuilder(PPC::LIS)
       .addReg(PPC::R11)
       .addExpr(LazyPtrHa16));
 
-    const MCExpr *LazyPtrLo16 =
-      MCSymbolRefExpr::Create(LazyPtr, MCSymbolRefExpr::VK_PPC_DARWIN_LO16,
-                              OutContext);
     // ldu r12, lo16(LazyPtr)(r11)
     // lwzu r12, lo16(LazyPtr)(r11)
+    const MCExpr *LazyPtrLo16 = PPCMCExpr::CreateLo16(LazyPtrExpr, OutContext);
     OutStreamer.EmitInstruction(MCInstBuilder(isPPC64 ? PPC::LDU : PPC::LWZU)
       .addReg(PPC::R12)
       .addExpr(LazyPtrLo16).addExpr(LazyPtrLo16)