[ThinLTO] Fix printing of WPD remarks

[tejohnson]

Summary

When WPD is performed in a ThinLTO backend, the function may be created
if it isn't already in that module. Module::getOrInsertFunction may
add a bitcast, in which case the returned Constant is not a Function and
doesn't have a name. Invoke stripPointerCasts() on the returned value
where we access its name.

[tejohnson]

ping

[pcc]

LGTM

lib/Transforms/IPO/WholeProgramDevirt.cpp

bool DevirtModule::tryFindVirtualCallTargets(
   return !TargetsForSlot.empty();
 }
 
 void DevirtModule::applySingleImplDevirt(VTableSlotInfo &SlotInfo,
                                          Constant *TheFn, bool &IsExported) {
   auto Apply = [&](CallSiteInfo &CSInfo) {
     for (auto &&VCallSite : CSInfo.CallSites) {
       if (RemarksEnabled)
-        VCallSite.emitRemark("single-impl", TheFn->getName(), OREGetter);
+        VCallSite.emitRemark("single-impl",
+                             TheFn->stripPointerCasts()->getName(), OREGetter);
       VCallSite.CS.setCalledFunction(ConstantExpr::getBitCast(
           TheFn, VCallSite.CS.getCalledValue()->getType()));
       // This use is no longer unsafe.
       if (VCallSite.NumUnsafeUses)
         --*VCallSite.NumUnsafeUses;
     }
     if (CSInfo.isExported())
       IsExported = true;
for (auto &&VCallSite : CSInfo.CallSites) {
 
       // Jump tables are only profitable if the retpoline mitigation is enabled.
       Attribute FSAttr = CS.getCaller()->getFnAttribute("target-features");
       if (FSAttr.hasAttribute(Attribute::None) ||
           !FSAttr.getValueAsString().contains("+retpoline"))
         continue;
 
       if (RemarksEnabled)
-        VCallSite.emitRemark("branch-funnel", JT->getName(), OREGetter);
+        VCallSite.emitRemark("branch-funnel",
+                             JT->stripPointerCasts()->getName(), OREGetter);
 
       // Pass the address of the vtable in the nest register, which is r10 on
       // x86_64.
       std::vector<Type *> NewArgs;
       NewArgs.push_back(Int8PtrTy);
       for (Type *T : CS.getFunctionType()->params())
         NewArgs.push_back(T);
       PointerType *NewFT = PointerType::getUnqual(

test/ThinLTO/X86/cfi-devirt.ll

 ; REQUIRES: x86-registered-target
 
 ; Test CFI devirtualization through the thin link and backend.
 
 ; RUN: opt -thinlto-bc -o %t.o %s
 
 ; Legacy PM
-; RUN: llvm-lto2 run %t.o -save-temps \
+; RUN: llvm-lto2 run %t.o -save-temps -pass-remarks=. \
 ; RUN:   -o %t3 \
 ; RUN:   -r=%t.o,test,px \
 ; RUN:   -r=%t.o,_ZN1A1nEi,p \
 ; RUN:   -r=%t.o,_ZN1B1fEi,p \
 ; RUN:   -r=%t.o,_ZN1C1fEi,p \
 ; RUN:   -r=%t.o,_ZTV1B, \
 ; RUN:   -r=%t.o,_ZTV1C, \
 ; RUN:   -r=%t.o,_ZN1A1nEi, \
 ; RUN:   -r=%t.o,_ZN1B1fEi, \
 ; RUN:   -r=%t.o,_ZN1C1fEi, \
 ; RUN:   -r=%t.o,_ZTV1B,px \
-; RUN:   -r=%t.o,_ZTV1C,px
+; RUN:   -r=%t.o,_ZTV1C,px 2>&1 | FileCheck %s --check-prefix=REMARK
 ; RUN: llvm-dis %t3.1.4.opt.bc -o - | FileCheck %s --check-prefix=CHECK-IR
 
 ; New PM
-; RUN: llvm-lto2 run %t.o -save-temps -use-new-pm \
+; RUN: llvm-lto2 run %t.o -save-temps -use-new-pm -pass-remarks=. \
 ; RUN:   -o %t3 \
 ; RUN:   -r=%t.o,test,px \
 ; RUN:   -r=%t.o,_ZN1A1nEi,p \
 ; RUN:   -r=%t.o,_ZN1B1fEi,p \
 ; RUN:   -r=%t.o,_ZN1C1fEi,p \
 ; RUN:   -r=%t.o,_ZTV1B, \
 ; RUN:   -r=%t.o,_ZTV1C, \
 ; RUN:   -r=%t.o,_ZN1A1nEi, \
 ; RUN:   -r=%t.o,_ZN1B1fEi, \
 ; RUN:   -r=%t.o,_ZN1C1fEi, \
 ; RUN:   -r=%t.o,_ZTV1B,px \
-; RUN:   -r=%t.o,_ZTV1C,px
+; RUN:   -r=%t.o,_ZTV1C,px 2>&1 | FileCheck %s --check-prefix=REMARK
 ; RUN: llvm-dis %t3.1.4.opt.bc -o - | FileCheck %s --check-prefix=CHECK-IR
 
+; REMARK: single-impl: devirtualized a call to _ZN1A1nEi
+
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-grtev4-linux-gnu"
 
 %struct.A = type { i32 (...)** }
 %struct.B = type { %struct.A }
 %struct.C = type { %struct.A }
 
 @_ZTV1B = constant { [4 x i8*] } { [4 x i8*] [i8* null, i8* undef, i8* bitcast (i32 (%struct.B*, i32)* @_ZN1B1fEi to i8*), i8* bitcast (i32 (%struct.A*, i32)* @_ZN1A1nEi to i8*)] }, !type !0, !type !1