Bitcode: Do not create FNENTRYs for aliases of functions.

[pcc]

Summary

There doesn't seem to be any point in doing this.

[tejohnson]

LGTM

I suspect this was needed before we had aliases summary entries

llvm/trunk/lib/Bitcode/Reader/BitcodeReader.cpp

while (true) {
     }
     case bitc::VST_CODE_FNENTRY: {
       // VST_CODE_FNENTRY: [valueid, offset, namechar x N]
       Expected<Value *> ValOrErr = recordValue(Record, 2, TT);
       if (Error Err = ValOrErr.takeError())
         return Err;
       Value *V = ValOrErr.get();
 
-      auto *GO = dyn_cast<GlobalObject>(V);
-      if (!GO) {
-        // If this is an alias, need to get the actual Function object
-        // it aliases, in order to set up the DeferredFunctionInfo entry below.
-        auto *GA = dyn_cast<GlobalAlias>(V);
-        if (GA)
-          GO = GA->getBaseObject();
-        assert(GO);
-      }
+      auto *F = dyn_cast<Function>(V);
+      // Ignore function offsets emitted for aliases of functions in older
+      // versions of LLVM.
+      if (!F)
+        break;
 
       // Note that we subtract 1 here because the offset is relative to one word
       // before the start of the identification or module block, which was
       // historically always the start of the regular bitcode header.
       uint64_t FuncWordOffset = Record[1] - 1;
-      Function *F = dyn_cast<Function>(GO);
-      assert(F);
       uint64_t FuncBitOffset = FuncWordOffset * 32;
       DeferredFunctionInfo[F] = FuncBitOffset + FuncBitcodeOffsetDelta;
       // Set the LastFunctionBlockBit to point to the last function block.
       // Later when parsing is resumed after function materialization,
       // we can simply skip that last function block.
       if (FuncBitOffset > LastFunctionBlockBit)
         LastFunctionBlockBit = FuncBitOffset;
       break;

llvm/trunk/lib/Bitcode/Writer/BitcodeWriter.cpp

for (const ValueName &Name : VST) {
     // Figure out the encoding to use for the name.
     StringEncoding Bits =
         getStringEncoding(Name.getKeyData(), Name.getKeyLength());
 
     unsigned AbbrevToUse = VST_ENTRY_8_ABBREV;
     NameVals.push_back(VE.getValueID(Name.getValue()));
 
     Function *F = dyn_cast<Function>(Name.getValue());
-    if (!F) {
-      // If value is an alias, need to get the aliased base object to
-      // see if it is a function.
-      auto *GA = dyn_cast<GlobalAlias>(Name.getValue());
-      if (GA && GA->getBaseObject())
-        F = dyn_cast<Function>(GA->getBaseObject());
-    }
 
     // VST_CODE_ENTRY:   [valueid, namechar x N]
     // VST_CODE_FNENTRY: [valueid, funcoffset, namechar x N]
     // VST_CODE_BBENTRY: [bbid, namechar x N]
     unsigned Code;
     if (isa<BasicBlock>(Name.getValue())) {
       Code = bitc::VST_CODE_BBENTRY;
       if (Bits == SE_Char6)

llvm/trunk/test/Bitcode/thinlto-function-summary.ll

 ; BC-NEXT: <PERMODULE {{.*}} op0=3 op1=7
 ; BC-NEXT: <PERMODULE {{.*}} op0=4 op1=16
 ; BC-NEXT: <ALIAS {{.*}} op0=5 op1=0 op2=3
 ; BC-NEXT: </GLOBALVAL_SUMMARY_BLOCK
 ; BC-NEXT: <VALUE_SYMTAB
 ; BC-NEXT: <FNENTRY {{.*}} op0=4 {{.*}}> record string = 'variadic'
 ; BC-NEXT: <FNENTRY {{.*}} op0=1 {{.*}}> record string = 'foo'
 ; BC-NEXT: <FNENTRY {{.*}} op0=2 {{.*}}> record string = 'bar'
-; BC-NEXT: <FNENTRY {{.*}} op0=5 {{.*}}> record string = 'f'
+; BC-NEXT: <ENTRY {{.*}} op0=5 {{.*}}> record string = 'f'
 ; BC-NEXT: <ENTRY {{.*}} record string = 'h'
 ; BC-NEXT: <FNENTRY {{.*}} op0=3 {{.*}}> record string = 'anon.
 
 
 ; RUN: opt -name-anon-globals -module-summary < %s | llvm-dis | FileCheck %s
 ; Check that this round-trips correctly.
 
 ; ModuleID = '<stdin>'