[clang] 6e4c1cf - [ThinLTO/WPD] Enable -wholeprogramdevirt-skip in ThinLTO backends

[Teresa Johnson via cfe-commits]

Author: Teresa Johnson
Date: 2020-11-24T09:35:07-08:00
New Revision: 6e4c1cf2938842ceefc2712f0007843369dd16ca

URL: https://github.com/llvm/llvm-project/commit/6e4c1cf2938842ceefc2712f0007843369dd16ca
DIFF: https://github.com/llvm/llvm-project/commit/6e4c1cf2938842ceefc2712f0007843369dd16ca.diff

LOG: [ThinLTO/WPD] Enable -wholeprogramdevirt-skip in ThinLTO backends

Previously this option could be used to skip devirtualizations of the
given functions in regular LTO and in the ThinLTO indexing step. This
change allows them to be skipped in the backend as well, which is useful
when debugging WPD in a distributed ThinLTO backend.

Differential Revision: https://reviews.llvm.org/D91812

Added: 
    

Modified: 
    clang/test/CodeGen/thinlto-distributed-cfi-devirt.ll
    llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp

Removed: 
    


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diff  --git a/clang/test/CodeGen/thinlto-distributed-cfi-devirt.ll b/clang/test/CodeGen/thinlto-distributed-cfi-devirt.ll
index 5c753ba6f93c..0a330a53e948 100644
--- a/clang/test/CodeGen/thinlto-distributed-cfi-devirt.ll
+++ b/clang/test/CodeGen/thinlto-distributed-cfi-devirt.ll
@@ -40,8 +40,16 @@
 ; CHECK-DIS: ^2 = typeid: (name: "_ZTS1A", summary: (typeTestRes: (kind: allOnes, sizeM1BitWidth: 7), wpdResolutions: ((offset: 0, wpdRes: (kind: branchFunnel)), (offset: 8, wpdRes: (kind: singleImpl, singleImplName: "_ZN1A1nEi"))))) ; guid = 7004155349499253778
 
 ; RUN: %clang_cc1 -triple x86_64-grtev4-linux-gnu \
-; RUN:   -emit-obj -fthinlto-index=%t.o.thinlto.bc -O2 \
-; RUN:   -emit-llvm -o - -x ir %t.o | FileCheck %s --check-prefixes=CHECK-IR
+; RUN:   -emit-obj -fthinlto-index=%t.o.thinlto.bc -O2 -Rpass=wholeprogramdevirt \
+; RUN:   -emit-llvm -o - -x ir %t.o 2>&1 | FileCheck %s --check-prefixes=CHECK-IR --check-prefixes=REMARKS
+
+; Check that the devirtualization is suppressed via -wholeprogramdevirt-skip
+; RUN: %clang_cc1 -triple x86_64-grtev4-linux-gnu -mllvm -wholeprogramdevirt-skip=_ZN1A1nEi \
+; RUN:   -emit-obj -fthinlto-index=%t.o.thinlto.bc -O2 -Rpass=wholeprogramdevirt \
+; RUN:   -emit-llvm -o - -x ir %t.o 2>&1 | FileCheck %s --check-prefixes=SKIP-IR --check-prefixes=SKIP-REMARKS
+
+; REMARKS: single-impl: devirtualized a call to _ZN1A1nEi
+; SKIP-REMARKS-NOT: single-impl
 
 ; Check that backend does not fail generating native code.
 ; RUN: %clang_cc1 -triple x86_64-grtev4-linux-gnu \
@@ -78,6 +86,7 @@ cont:
 
   ; Check that the call was devirtualized.
   ; CHECK-IR: %call = tail call i32 @_ZN1A1nEi
+  ; SKIP-IR-NOT: %call = tail call i32 @_ZN1A1nEi
   %call = tail call i32 %4(%struct.A* nonnull %obj, i32 %a)
   %vtable16 = load i8*, i8** %0
   %5 = tail call { i8*, i1 } @llvm.type.checked.load(i8* %vtable16, i32 0, metadata !"_ZTS1A")

diff  --git a/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp b/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
index e97f1acbb396..5350d85e11f3 100644
--- a/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
+++ b/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
@@ -1030,6 +1030,10 @@ bool DevirtIndex::tryFindVirtualCallTargets(
 
 void DevirtModule::applySingleImplDevirt(VTableSlotInfo &SlotInfo,
                                          Constant *TheFn, bool &IsExported) {
+  // Don't devirtualize function if we're told to skip it
+  // in -wholeprogramdevirt-skip.
+  if (FunctionsToSkip.match(TheFn->stripPointerCasts()->getName()))
+    return;
   auto Apply = [&](CallSiteInfo &CSInfo) {
     for (auto &&VCallSite : CSInfo.CallSites) {
       if (RemarksEnabled)