Prevent alias from pointing to weak aliases.

This adds back r204781.

Original message:

Aliases are just another name for a position in a file. As such, the
regular symbol resolutions are not applied. For example, given

define void @my_func() {
  ret void
}
@my_alias = alias weak void ()* @my_func
@my_alias2 = alias void ()* @my_alias

We produce without this patch:

        .weak   my_alias
my_alias = my_func
        .globl  my_alias2
my_alias2 = my_alias

That is, in the resulting ELF file my_alias, my_func and my_alias are
just 3 names pointing to offset 0 of .text. That is *not* the
semantics of IR linking. For example, linking in a

@my_alias = alias void ()* @other_func

would require the strong my_alias to override the weak one and
my_alias2 would end up pointing to other_func.

There is no way to represent that with aliases being just another
name, so the best solution seems to be to just disallow it, converting
a miscompile into an error.

llvm-svn: 204934

1 files changed, 6 insertions, 6 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp b/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
index daf90c86ef9..9ce8ea911cf 100644
--- a/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
+++ b/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
@@ -381,8 +381,8 @@ void PPCAsmPrinter::EmitInstruction(const MachineInstr *MI) {
     if (MO.isGlobal()) {
       const GlobalValue *GValue = MO.getGlobal();
       const GlobalAlias *GAlias = dyn_cast<GlobalAlias>(GValue);
-      const GlobalValue *RealGValue = GAlias ?
-        GAlias->resolveAliasedGlobal(false) : GValue;
+      const GlobalValue *RealGValue =
+          GAlias ? GAlias->getAliasedGlobal() : GValue;
       MOSymbol = getSymbol(RealGValue);
       const GlobalVariable *GVar = dyn_cast<GlobalVariable>(RealGValue);
       IsExternal = GVar && !GVar->hasInitializer();
@@ -428,8 +428,8 @@ void PPCAsmPrinter::EmitInstruction(const MachineInstr *MI) {
     else if (MO.isGlobal()) {
       const GlobalValue *GValue = MO.getGlobal();
       const GlobalAlias *GAlias = dyn_cast<GlobalAlias>(GValue);
-      const GlobalValue *RealGValue = GAlias ?
-        GAlias->resolveAliasedGlobal(false) : GValue;
+      const GlobalValue *RealGValue =
+          GAlias ? GAlias->getAliasedGlobal() : GValue;
       MOSymbol = getSymbol(RealGValue);
       const GlobalVariable *GVar = dyn_cast<GlobalVariable>(RealGValue);
     
@@ -463,8 +463,8 @@ void PPCAsmPrinter::EmitInstruction(const MachineInstr *MI) {
     if (MO.isGlobal()) {
       const GlobalValue *GValue = MO.getGlobal();
       const GlobalAlias *GAlias = dyn_cast<GlobalAlias>(GValue);
-      const GlobalValue *RealGValue = GAlias ?
-        GAlias->resolveAliasedGlobal(false) : GValue;
+      const GlobalValue *RealGValue =
+          GAlias ? GAlias->getAliasedGlobal() : GValue;
       MOSymbol = getSymbol(RealGValue);
       const GlobalVariable *GVar = dyn_cast<GlobalVariable>(RealGValue);
       IsExternal = GVar && !GVar->hasInitializer();