[llvm] 6d2032e - [WPD] Provide a way to prevent functions from being devirtualized
via llvm-commits
llvm-commits at lists.llvm.org
Mon Mar 9 04:20:07 PDT 2020
Author: evgeny
Date: 2020-03-09T14:05:15+03:00
New Revision: 6d2032e259c70a77679e47c52b6b2b35413a4f25
URL: https://github.com/llvm/llvm-project/commit/6d2032e259c70a77679e47c52b6b2b35413a4f25
DIFF: https://github.com/llvm/llvm-project/commit/6d2032e259c70a77679e47c52b6b2b35413a4f25.diff
LOG: [WPD] Provide a way to prevent functions from being devirtualized
Differential revision: https://reviews.llvm.org/D75617
Added:
Modified:
llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
llvm/test/ThinLTO/X86/devirt.ll
llvm/test/Transforms/WholeProgramDevirt/virtual-const-prop-check.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp b/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
index bbc1433a22e8..b1905e2af05a 100644
--- a/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
+++ b/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
@@ -91,6 +91,7 @@
#include "llvm/Support/Errc.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/GlobPattern.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/IPO/FunctionAttrs.h"
@@ -156,6 +157,29 @@ cl::opt<bool> DisableWholeProgramVisibility(
cl::ZeroOrMore,
cl::desc("Disable whole program visibility (overrides enabling options)"));
+/// Provide way to prevent certain function from being devirtualized
+cl::list<std::string>
+ SkipFunctionNames("wholeprogramdevirt-skip",
+ cl::desc("Prevent function(s) from being devirtualized"),
+ cl::Hidden, cl::ZeroOrMore, cl::CommaSeparated);
+
+namespace {
+struct PatternList {
+ std::vector<GlobPattern> Patterns;
+ template <class T> void init(const T &StringList) {
+ for (const auto &S : StringList)
+ if (Expected<GlobPattern> Pat = GlobPattern::create(S))
+ Patterns.push_back(std::move(*Pat));
+ }
+ bool match(StringRef S) {
+ for (const GlobPattern &P : Patterns)
+ if (P.match(S))
+ return true;
+ return false;
+ }
+};
+} // namespace
+
// Find the minimum offset that we may store a value of size Size bits at. If
// IsAfter is set, look for an offset before the object, otherwise look for an
// offset after the object.
@@ -491,6 +515,7 @@ struct DevirtModule {
// eliminate the type check by RAUWing the associated llvm.type.test call with
// true.
std::map<CallInst *, unsigned> NumUnsafeUsesForTypeTest;
+ PatternList FunctionsToSkip;
DevirtModule(Module &M, function_ref<AAResults &(Function &)> AARGetter,
function_ref<OptimizationRemarkEmitter &(Function *)> OREGetter,
@@ -506,6 +531,7 @@ struct DevirtModule {
IntPtrTy(M.getDataLayout().getIntPtrType(M.getContext(), 0)),
RemarksEnabled(areRemarksEnabled()), OREGetter(OREGetter) {
assert(!(ExportSummary && ImportSummary));
+ FunctionsToSkip.init(SkipFunctionNames);
}
bool areRemarksEnabled();
@@ -614,12 +640,16 @@ struct DevirtIndex {
MapVector<VTableSlotSummary, VTableSlotInfo> CallSlots;
+ PatternList FunctionsToSkip;
+
DevirtIndex(
ModuleSummaryIndex &ExportSummary,
std::set<GlobalValue::GUID> &ExportedGUIDs,
std::map<ValueInfo, std::vector<VTableSlotSummary>> &LocalWPDTargetsMap)
: ExportSummary(ExportSummary), ExportedGUIDs(ExportedGUIDs),
- LocalWPDTargetsMap(LocalWPDTargetsMap) {}
+ LocalWPDTargetsMap(LocalWPDTargetsMap) {
+ FunctionsToSkip.init(SkipFunctionNames);
+ }
bool tryFindVirtualCallTargets(std::vector<ValueInfo> &TargetsForSlot,
const TypeIdCompatibleVtableInfo TIdInfo,
@@ -926,6 +956,9 @@ bool DevirtModule::tryFindVirtualCallTargets(
if (!Fn)
return false;
+ if (FunctionsToSkip.match(Fn->getName()))
+ return false;
+
// We can disregard __cxa_pure_virtual as a possible call target, as
// calls to pure virtuals are UB.
if (Fn->getName() == "__cxa_pure_virtual")
@@ -1105,6 +1138,11 @@ bool DevirtIndex::trySingleImplDevirt(MutableArrayRef<ValueInfo> TargetsForSlot,
if (!Size)
return false;
+ // Don't devirtualize function if we're told to skip it
+ // in -wholeprogramdevirt-skip.
+ if (FunctionsToSkip.match(TheFn.name()))
+ return false;
+
// If the summary list contains multiple summaries where at least one is
// a local, give up, as we won't know which (possibly promoted) name to use.
for (auto &S : TheFn.getSummaryList())
diff --git a/llvm/test/ThinLTO/X86/devirt.ll b/llvm/test/ThinLTO/X86/devirt.ll
index c24685c5d6bf..0a389f3ee638 100644
--- a/llvm/test/ThinLTO/X86/devirt.ll
+++ b/llvm/test/ThinLTO/X86/devirt.ll
@@ -47,6 +47,21 @@
; RUN: -r=%t2.o,_ZTV1D,px 2>&1 | FileCheck %s --check-prefix=REMARK
; RUN: llvm-dis %t3.1.4.opt.bc -o - | FileCheck %s --check-prefix=CHECK-IR
+; Check that we're able to prevent specific function from being
+; devirtualized when running index based WPD.
+; RUN: llvm-lto2 run %t2.o -save-temps -pass-remarks=. \
+; RUN: -whole-program-visibility \
+; RUN: -wholeprogramdevirt-skip=_ZN1A1nEi \
+; RUN: -o %t3 \
+; RUN: -r=%t2.o,test,px \
+; RUN: -r=%t2.o,_ZN1A1nEi,p \
+; RUN: -r=%t2.o,_ZN1B1fEi,p \
+; RUN: -r=%t2.o,_ZN1C1fEi,p \
+; RUN: -r=%t2.o,_ZN1D1mEi,p \
+; RUN: -r=%t2.o,_ZTV1B,px \
+; RUN: -r=%t2.o,_ZTV1C,px \
+; RUN: -r=%t2.o,_ZTV1D,px 2>&1 | FileCheck %s --check-prefix=SKIP
+
; New PM, Index based WPD
; RUN: llvm-lto2 run %t2.o -save-temps -use-new-pm -pass-remarks=. \
; RUN: -whole-program-visibility \
@@ -110,6 +125,8 @@
; REMARK-DAG: single-impl: devirtualized a call to _ZN1A1nEi
; REMARK-DAG: single-impl: devirtualized a call to _ZN1D1mEi
+; SKIP-NOT: devirtualized a call to _ZN1A1nEi
+
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-grtev4-linux-gnu"
diff --git a/llvm/test/Transforms/WholeProgramDevirt/virtual-const-prop-check.ll b/llvm/test/Transforms/WholeProgramDevirt/virtual-const-prop-check.ll
index b7537f26e4d0..de432260f40e 100644
--- a/llvm/test/Transforms/WholeProgramDevirt/virtual-const-prop-check.ll
+++ b/llvm/test/Transforms/WholeProgramDevirt/virtual-const-prop-check.ll
@@ -1,4 +1,12 @@
; RUN: opt -S -wholeprogramdevirt -whole-program-visibility -pass-remarks=wholeprogramdevirt %s 2>&1 | FileCheck %s
+; Skipping vf0i1 is identical to setting public LTO visibility. We don't devirtualize vf0i1 and all other
+; virtual call targets.
+; RUN: opt -S -wholeprogramdevirt -whole-program-visibility -pass-remarks=wholeprogramdevirt -wholeprogramdevirt-skip=vf0i1 %s 2>&1 | FileCheck %s --check-prefix=SKIP
+; We have two set of call targets {vf0i1, vf1i1} and {vf1i32, vf2i32, vf3i32, vf4i32}.
+; The command below prevents both of them from devirtualization.
+; RUN: opt -S -wholeprogramdevirt -whole-program-visibility -pass-remarks=wholeprogramdevirt -wholeprogramdevirt-skip=vf0i1,vf1i32 %s 2>&1 | FileCheck %s --check-prefix=SKIP-ALL
+; Check wildcard
+; RUN: opt -S -wholeprogramdevirt -whole-program-visibility -pass-remarks=wholeprogramdevirt -wholeprogramdevirt-skip=vf?i1 %s 2>&1 | FileCheck %s --check-prefix=SKIP
target datalayout = "e-p:64:64"
target triple = "x86_64-unknown-linux-gnu"
@@ -14,6 +22,15 @@ target triple = "x86_64-unknown-linux-gnu"
; CHECK: remark: <unknown>:0:0: devirtualized vf4i32
; CHECK-NOT: devirtualized
+; SKIP: remark: <unknown>:0:0: virtual-const-prop: devirtualized a call to vf1i32
+; SKIP: remark: <unknown>:0:0: devirtualized vf1i32
+; SKIP: remark: <unknown>:0:0: devirtualized vf2i32
+; SKIP: remark: <unknown>:0:0: devirtualized vf3i32
+; SKIP: remark: <unknown>:0:0: devirtualized vf4i32
+; SKIP-NOT: devirtualized
+
+; SKIP-ALL-NOT: devirtualized
+
; 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*),
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