Print remarks from WholeProgramDevirt pass for each call site.

[krasin]

Summary

It's useful to have some visibility about which call sites are devirtualized,
especially for debug purposes. Another use case is a regression test on the
application side (like, Chromium).

[pcc]

Please add a negative test. You can piggyback on one of the many negative tests in the test/Transforms/WholeProgramDevirt directory.

lib/Transforms/IPO/WholeProgramDevirt.cpp

403

There should also be a remark emitted in this case.

test/Transforms/WholeProgramDevirt/virtual-const-prop-check.ll

6

These lines won't be matched against unless you prefix them with CHECK:.

[krasin]

Add negative test; fix positive test (add CHECK:)

[pcc]

lib/Transforms/IPO/WholeProgramDevirt.cpp

403

Please address this and add a test for this case.

test/Transforms/WholeProgramDevirt/non-constant-vtable.ll

1

I think you need -pass-remarks=wholeprogramdevirt here.

[krasin]

Fix negative test; add remarks for single use case.

[krasin]

Thank you for all the catches. Hopefully, all the comments are now addressed. Please, take another look.

[pcc]

LGTM

lib/Transforms/IPO/WholeProgramDevirt.cpp

 #include "llvm/Transforms/IPO/WholeProgramDevirt.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/MapVector.h"
 #include "llvm/Analysis/TypeMetadataUtils.h"
 #include "llvm/IR/CallSite.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/Intrinsics.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Pass.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Transforms/IPO.h"
 #include "llvm/Transforms/Utils/Evaluator.h"
struct VirtualCallSite {
   CallSite CS;
 
   // If non-null, this field points to the associated unsafe use count stored in
   // the DevirtModule::NumUnsafeUsesForTypeTest map below. See the description
   // of that field for details.
   unsigned *NumUnsafeUses;
 
   void replaceAndErase(Value *New) {
+    Function *F = CS.getCaller();
+    emitOptimizationRemark(F->getContext(), DEBUG_TYPE, *F,
+                           CS.getInstruction()->getDebugLoc(),
+                           "devirtualized call");
+
     CS->replaceAllUsesWith(New);
     if (auto II = dyn_cast<InvokeInst>(CS.getInstruction())) {
       BranchInst::Create(II->getNormalDest(), CS.getInstruction());
       II->getUnwindDest()->removePredecessor(II->getParent());
     }
     CS->eraseFromParent();
     // This use is no longer unsafe.
     if (NumUnsafeUses)
bool DevirtModule::trySingleImplDevirt(
   // function.
   Function *TheFn = TargetsForSlot[0].Fn;
   for (auto &&Target : TargetsForSlot)
     if (TheFn != Target.Fn)
       return false;
 
   // If so, update each call site to call that implementation directly.
   for (auto &&VCallSite : CallSites) {
     VCallSite.CS.setCalledFunction(ConstantExpr::getBitCast(
         TheFn, VCallSite.CS.getCalledValue()->getType()));
     // This use is no longer unsafe.
     if (VCallSite.NumUnsafeUses)
       --*VCallSite.NumUnsafeUses;
   }
   return true;
 }
 

test/Transforms/WholeProgramDevirt/non-constant-vtable.ll

-; RUN: opt -S -wholeprogramdevirt %s | FileCheck %s
+; RUN: opt -S -wholeprogramdevirt %s 2>&1 | FileCheck %s
+
+; CHECK-NOT: devirtualized call
 
 target datalayout = "e-p:64:64"
 target triple = "x86_64-unknown-linux-gnu"
 
 @vt = global [1 x i8*] [i8* bitcast (void (i8*)* @vf to i8*)], !type !0
 
 define void @vf(i8* %this) {
   ret void

test/Transforms/WholeProgramDevirt/virtual-const-prop-check.ll

-; RUN: opt -S -wholeprogramdevirt %s | FileCheck %s
+; RUN: opt -S -wholeprogramdevirt -pass-remarks=wholeprogramdevirt %s 2>&1 | FileCheck %s
 
 target datalayout = "e-p:64:64"
 target triple = "x86_64-unknown-linux-gnu"
 
+; CHECK: remark: <unknown>:0:0: devirtualized call
+; CHECK: remark: <unknown>:0:0: devirtualized call
+; CHECK: remark: <unknown>:0:0: devirtualized call
+
 ; CHECK: [[VT1DATA:@[^ ]*]] = private constant { [8 x i8], [3 x i8*], [0 x i8] } { [8 x i8] c"\00\00\00\01\01\00\00\00", [3 x i8*] [i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i32 (i8*)* @vf1i32 to i8*)], [0 x i8] zeroinitializer }, section "vt1sec", !type [[T8:![0-9]+]]
 @vt1 = constant [3 x i8*] [
 i8* bitcast (i1 (i8*)* @vf0i1 to i8*),
 i8* bitcast (i1 (i8*)* @vf1i1 to i8*),
 i8* bitcast (i32 (i8*)* @vf1i32 to i8*)
 ], section "vt1sec", !type !0
 
 ; CHECK: [[VT2DATA:@[^ ]*]] = private constant { [8 x i8], [3 x i8*], [0 x i8] } { [8 x i8] c"\00\00\00\02\02\00\00\00", [3 x i8*] [i8* bitcast (i1 (i8*)* @vf1i1 to i8*), i8* bitcast (i1 (i8*)* @vf0i1 to i8*), i8* bitcast (i32 (i8*)* @vf2i32 to i8*)], [0 x i8] zeroinitializer }, !type [[T8]]