[PATCH] D129009: [LTO] Fix LTO for aliased IFuncs

[Schrodinger ZHU Yifan via Phabricator via cfe-commits]

SchrodingerZhu updated this revision to Diff 441891.
SchrodingerZhu added a comment.

fix liveness of resolvers


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D129009/new/

https://reviews.llvm.org/D129009

Files:
  llvm/lib/Analysis/ModuleSummaryAnalysis.cpp
  llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
  llvm/lib/Transforms/IPO/FunctionImport.cpp
  llvm/test/LTO/Resolution/X86/alias-indirect-function-lto.ll


Index: llvm/test/LTO/Resolution/X86/alias-indirect-function-lto.ll
===================================================================
--- /dev/null
+++ llvm/test/LTO/Resolution/X86/alias-indirect-function-lto.ll
@@ -0,0 +1,22 @@
+; RUN: opt -module-summary -o %t.bc %s
+; RUN: llvm-lto2 run %t.bc -r %t.bc,foo,pl -r %t.bc,bar,pl -r %t.bc,baz,pl -o %t2
+; RUN: llvm-nm %t2.1 | FileCheck %s
+; CHECK: i bar
+; CHECK: i baz
+; CHECK: i foo
+; CHECK: t foo_resolver
+
+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-unknown-linux-gnu"
+
+ at foo = ifunc i32 (i32), i32 (i32)* ()* @foo_resolver
+
+define internal i32 (i32)* @foo_resolver() {
+entry:
+  ret i32 (i32)* null
+}
+
+ at bar = alias i32 (i32), i32 (i32)* @foo
+
+ at baz = weak alias i32 (i32), i32 (i32)* @foo
+; no crash
Index: llvm/lib/Transforms/IPO/FunctionImport.cpp
===================================================================
--- llvm/lib/Transforms/IPO/FunctionImport.cpp
+++ llvm/lib/Transforms/IPO/FunctionImport.cpp
@@ -1147,6 +1147,12 @@
   // Declare a callback for the internalize pass that will ask for every
   // candidate GlobalValue if it can be internalized or not.
   auto MustPreserveGV = [&](const GlobalValue &GV) -> bool {
+    // It maybe the case that the symbol is aliasing an ifunc where
+    // the summary is not available.
+    if (isa<GlobalAlias>(&GV) &&
+        isa<GlobalIFunc>(dyn_cast<GlobalAlias>(&GV)->getAliasee()))
+      return true;
+
     // Lookup the linkage recorded in the summaries during global analysis.
     auto GS = DefinedGlobals.find(GV.getGUID());
     if (GS == DefinedGlobals.end()) {
Index: llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
===================================================================
--- llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -4103,8 +4103,9 @@
 
   for (const GlobalAlias &A : M.aliases()) {
     auto *Aliasee = A.getAliaseeObject();
-    if (!Aliasee->hasName())
-      // Nameless function don't have an entry in the summary, skip it.
+    // IFunc function and Nameless function don't have an entry in the
+    // summary, skip it.
+    if (!Aliasee->hasName() || isa<GlobalIFunc>(Aliasee))
       continue;
     auto AliasId = VE.getValueID(&A);
     auto AliaseeId = VE.getValueID(Aliasee);
Index: llvm/lib/Analysis/ModuleSummaryAnalysis.cpp
===================================================================
--- llvm/lib/Analysis/ModuleSummaryAnalysis.cpp
+++ llvm/lib/Analysis/ModuleSummaryAnalysis.cpp
@@ -646,15 +646,20 @@
   Index.addGlobalValueSummary(V, std::move(GVarSummary));
 }
 
-static void
-computeAliasSummary(ModuleSummaryIndex &Index, const GlobalAlias &A,
-                    DenseSet<GlobalValue::GUID> &CantBePromoted) {
+static void computeAliasSummary(ModuleSummaryIndex &Index, const GlobalAlias &A,
+                                DenseSet<GlobalValue::GUID> &CantBePromoted) {
+  auto *Aliasee = A.getAliaseeObject();
+
+  // Skip summary for indirect function aliases as summary for aliasee will not
+  // be emitted.
+  if (isa<GlobalIFunc>(Aliasee))
+    return;
+
   bool NonRenamableLocal = isNonRenamableLocal(A);
   GlobalValueSummary::GVFlags Flags(
       A.getLinkage(), A.getVisibility(), NonRenamableLocal,
       /* Live = */ false, A.isDSOLocal(), A.canBeOmittedFromSymbolTable());
   auto AS = std::make_unique<AliasSummary>(Flags);
-  auto *Aliasee = A.getAliaseeObject();
   auto AliaseeVI = Index.getValueInfo(Aliasee->getGUID());
   assert(AliaseeVI && "Alias expects aliasee summary to be available");
   assert(AliaseeVI.getSummaryList().size() == 1 &&
@@ -811,6 +816,10 @@
   for (const GlobalAlias &A : M.aliases())
     computeAliasSummary(Index, A, CantBePromoted);
 
+  // Iterate through ifuncs, set their resolvers all alive.
+  for (const GlobalIFunc &I : M.ifuncs())
+    Index.getGlobalValueSummary(*I.getResolverFunction())->setLive(true);
+
   for (auto *V : LocalsUsed) {
     auto *Summary = Index.getGlobalValueSummary(*V);
     assert(Summary && "Missing summary for global value");


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