[PATCH] D18658: [AsmPrinter] Print aliases in topological order

[Tim Shen via llvm-commits]

timshen updated this revision to Diff 52296.
timshen marked an inline comment as done.
timshen added a comment.

Removed unnecessary braces.


http://reviews.llvm.org/D18658

Files:
  lib/CodeGen/AsmPrinter/AsmPrinter.cpp
  test/CodeGen/Generic/asm-printer-topological-order.ll

Index: test/CodeGen/Generic/asm-printer-topological-order.ll
===================================================================
--- /dev/null
+++ test/CodeGen/Generic/asm-printer-topological-order.ll
@@ -0,0 +1,15 @@
+; RUN: llc < %s | FileCheck %s
+
+ at TestA = alias void (), void ()* @TestC
+ at TestB = alias void (), void ()* @TestC
+ at TestC = alias void (), void ()* @TestD
+
+define void @TestD() {
+entry:
+  ret void
+}
+
+; CHECK-LABEL: TestD:
+; CHECK: TestC = TestD
+; CHECK-DAG: TestB = TestC
+; CHECK-DAG: TestA = TestC
Index: lib/CodeGen/AsmPrinter/AsmPrinter.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -1148,7 +1148,7 @@
   }
 
   OutStreamer->AddBlankLine();
-  for (const auto &Alias : M.aliases()) {
+  const auto printAlias = [this, &M](const GlobalAlias &Alias) {
     MCSymbol *Name = getSymbol(&Alias);
 
     if (Alias.hasExternalLinkage() || !MAI->getWeakRefDirective())
@@ -1186,6 +1186,23 @@
       OutStreamer->emitELFSize(cast<MCSymbolELF>(Name),
                                MCConstantExpr::create(Size, OutContext));
     }
+  };
+  // Print aliases in topological order, that is, for each alias a = b,
+  // b must be printed before a.
+  // This is because on some targets (e.g. PowerPC) linker expects aliases in
+  // such an order to generate correct TOC information.
+  SmallVector<const GlobalAlias *, 16> AliasStack;
+  SmallPtrSet<const GlobalAlias *, 16> AliasVisited;
+  for (const auto &Alias : M.aliases()) {
+    for (const GlobalAlias *Cur = &Alias; Cur;
+         Cur = dyn_cast<GlobalAlias>(Cur->getAliasee())) {
+      if (!AliasVisited.insert(Cur).second)
+        break;
+      AliasStack.push_back(Cur);
+    }
+    for (const GlobalAlias *AncestorAlias : reverse(AliasStack))
+      printAlias(*AncestorAlias);
+    AliasStack.clear();
   }
 
   GCModuleInfo *MI = getAnalysisIfAvailable<GCModuleInfo>();


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