Reject alias to undefined symbols in the verifier.

On ELF and COFF an alias is just another name for a position in the file.
There is no way to refer to a position in another file, so an alias to
undefined is meaningless.

MachO currently doesn't support aliases. The spec has a N_INDR, which when
implemented will have a different set of restrictions. Adding support for
it shouldn't be harder than any other IR extension.

For now, having the IR represent what is actually possible with current
tools makes it easier to fix the design of GlobalAlias.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203705 91177308-0d34-0410-b5e6-96231b3b80d8

17 files changed, 166 insertions, 63 deletions

diff --git a/docs/LangRef.rst b/docs/LangRef.rst
index cf1243a04b..0a46e8375e 100644
--- a/docs/LangRef.rst
+++ b/docs/LangRef.rst
@@ -687,6 +687,11 @@ The linkage must be one of ``private``, ``linker_private``,
 might not correctly handle dropping a weak symbol that is aliased by a non-weak
 alias.
 
+Alias that are not ``unnamed_addr`` are guaranteed to have the same address as
+the aliasee.
+
+The aliasee must be a definition.
+
 .. _namedmetadatastructure:
 
 Named Metadata
diff --git a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index ebca8e544b..66ce4e1075 100644
--- a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -928,11 +928,7 @@ bool AsmPrinter::doFinalization(Module &M) {
       MCSymbol *Name = getSymbol(I);
 
       const GlobalValue *GV = I->getAliasedGlobal();
-      if (GV->isDeclaration()) {
-        report_fatal_error(Name->getName() +
-                           ": Target doesn't support aliases to declarations");
-      }
-
+      assert(!GV->isDeclaration());
       MCSymbol *Target = getSymbol(GV);
 
       if (I->hasExternalLinkage() || !MAI->getWeakRefDirective())
diff --git a/lib/IR/Verifier.cpp b/lib/IR/Verifier.cpp
index fcdbac2f9f..2fc77cc2d7 100644
--- a/lib/IR/Verifier.cpp
+++ b/lib/IR/Verifier.cpp
@@ -501,6 +501,7 @@ void Verifier::visitGlobalAlias(const GlobalAlias &GA) {
               &GA);
     }
   }
+  Assert1(!GV->isDeclaration(), "Alias must point to a definition", &GA);
 
   const GlobalValue* Resolved = GA.resolveAliasedGlobal(/*stopOnWeak*/ false);
   Assert1(Resolved,
diff --git a/test/Analysis/BasicAA/2007-11-05-SizeCrash.ll b/test/Analysis/BasicAA/2007-11-05-SizeCrash.ll
index 563d332636..32d9930f42 100644
--- a/test/Analysis/BasicAA/2007-11-05-SizeCrash.ll
+++ b/test/Analysis/BasicAA/2007-11-05-SizeCrash.ll
@@ -7,7 +7,7 @@ target triple = "x86_64-unknown-linux-gnu"
         %struct.pci_device_id = type { i32, i32, i32, i32, i32, i32, i64 }
         %struct.usb_bus = type { %struct.device* }
         %struct.usb_hcd = type { %struct.usb_bus, i64, [0 x i64] }
-@uhci_pci_ids = external constant [1 x %struct.pci_device_id]           ; <[1 x %struct.pci_device_id]*> [#uses=1]
+@uhci_pci_ids = constant [1 x %struct.pci_device_id] zeroinitializer
 
 @__mod_pci_device_table = alias [1 x %struct.pci_device_id]* @uhci_pci_ids     
         ; <[1 x %struct.pci_device_id]*> [#uses=0]
diff --git a/test/Analysis/BasicAA/2007-12-08-OutOfBoundsCrash.ll b/test/Analysis/BasicAA/2007-12-08-OutOfBoundsCrash.ll
index 52d0af1b81..cd997ea525 100644
--- a/test/Analysis/BasicAA/2007-12-08-OutOfBoundsCrash.ll
+++ b/test/Analysis/BasicAA/2007-12-08-OutOfBoundsCrash.ll
@@ -7,7 +7,7 @@ target triple = "x86_64-unknown-linux-gnu"
 	%struct.pci_device_id = type { i32, i32, i32, i32, i32, i32, i64 }
 	%struct.usb_bus = type { %struct.device* }
 	%struct.usb_hcd = type { %struct.usb_bus, [0 x i64] }
-@pci_ids = external constant [1 x %struct.pci_device_id]		; <[1 x %struct.pci_device_id]*> [#uses=1]
+@pci_ids = constant [1 x %struct.pci_device_id] zeroinitializer
 
 @__mod_pci_device_table = alias [1 x %struct.pci_device_id]* @pci_ids		; <[1 x %struct.pci_device_id]*> [#uses=0]
 
diff --git a/test/Assembler/2007-09-10-AliasFwdRef.ll b/test/Assembler/2007-09-10-AliasFwdRef.ll
index b21491ba5a..2ebfc2719e 100644
--- a/test/Assembler/2007-09-10-AliasFwdRef.ll
+++ b/test/Assembler/2007-09-10-AliasFwdRef.ll
@@ -6,4 +6,6 @@
 
 
 
-declare extern_weak i32 @pthread_cancel(i32)
+define weak i32 @pthread_cancel(i32) {
+  ret i32 0
+}
diff --git a/test/CodeGen/X86/2008-03-14-SpillerCrash.ll b/test/CodeGen/X86/2008-03-14-SpillerCrash.ll
index 18b3714f85..6b374a7f6f 100644
--- a/test/CodeGen/X86/2008-03-14-SpillerCrash.ll
+++ b/test/CodeGen/X86/2008-03-14-SpillerCrash.ll
@@ -6,7 +6,7 @@
 	%struct.locale_data = type { i8*, i8*, i32, i32, { void (%struct.locale_data*)*, %struct.anon }, i32, i32, i32, [0 x %struct.locale_data_value] }
 	%struct.locale_data_value = type { i32* }
 
-@wcstoll_l = alias i64 (i32*, i32**, i32, %struct.__locale_struct*)* @__wcstoll_l		; <i64 (i32*, i32**, i32, %struct.__locale_struct*)*> [#uses=0]
+@wcstoll_l = alias i64 (i32*, i32**, i32, %struct.__locale_struct*)* @__wcstoll_l
 
 define i64 @____wcstoll_l_internal(i32* %nptr, i32** %endptr, i32 %base, i32 %group, %struct.__locale_struct* %loc) nounwind  {
 entry:
diff --git a/test/CodeGen/X86/alias-error.ll b/test/CodeGen/X86/alias-error.ll
deleted file mode 100644
index 8f01dcff2b..0000000000
--- a/test/CodeGen/X86/alias-error.ll
+++ /dev/null
@@ -1,5 +0,0 @@
-; RUN: not llc -mtriple=i686-pc-linux-gnu %s -o /dev/null 2>&1 | FileCheck %s
-
-@a = external global i32
-@b = alias i32* @a
-; CHECK: b: Target doesn't support aliases to declarations
diff --git a/test/Feature/aliases.ll b/test/Feature/aliases.ll
index 139381215e..7ffa5f2601 100644
--- a/test/Feature/aliases.ll
+++ b/test/Feature/aliases.ll
@@ -4,14 +4,16 @@
 
 @llvm.used = appending global [1 x i8*] [i8* bitcast (i32* @foo1 to i8*)], section "llvm.metadata"
 
-@bar = external global i32
+@bar = global i32 0
 @foo1 = alias i32* @bar
 @foo2 = alias i32* @bar
 @foo3 = alias i32* @foo2
 
 %FunTy = type i32()
 
-declare i32 @foo_f()
+define i32 @foo_f() {
+  ret i32 0
+}
 @bar_f = alias weak %FunTy* @foo_f
 @bar_ff = alias i32()* @bar_f
 
diff --git a/test/Linker/2011-08-22-ResolveAlias2.ll b/test/Linker/2011-08-22-ResolveAlias2.ll
index 2549040597..eee60d49d0 100644
--- a/test/Linker/2011-08-22-ResolveAlias2.ll
+++ b/test/Linker/2011-08-22-ResolveAlias2.ll
@@ -37,56 +37,110 @@
 @_ZL33__gthrw_pthread_mutexattr_settypeP19pthread_mutexattr_ti = alias weak i32 (%union.pthread_mutexattr_t*, i32)* @pthread_mutexattr_settype
 @_ZL33__gthrw_pthread_mutexattr_destroyP19pthread_mutexattr_t = alias weak i32 (%union.pthread_mutexattr_t*)* @pthread_mutexattr_destroy
 
-declare void @_ZN13HexxagonBoardC2ERKS_(%struct.HexxagonBoard*, %struct.HexxagonBoard*) uwtable align 2
+define void @_ZN13HexxagonBoardC2ERKS_(%struct.HexxagonBoard*, %struct.HexxagonBoard*) uwtable align 2 {
+  ret void
+}
 
-declare extern_weak i32 @pthread_once(i32*, void ()*)
+define weak i32 @pthread_once(i32*, void ()*) {
+  ret i32 0
+}
 
-declare extern_weak i8* @pthread_getspecific(i32)
+define weak i8* @pthread_getspecific(i32) {
+  ret i8* null
+}
 
-declare extern_weak i32 @pthread_setspecific(i32, i8*)
+define weak i32 @pthread_setspecific(i32, i8*) {
+  ret i32 0
+}
 
-declare extern_weak i32 @pthread_create(i64*, %union.pthread_attr_t*, i8* (i8*)*, i8*)
+define weak i32 @pthread_create(i64*, %union.pthread_attr_t*, i8* (i8*)*, i8*) {
+  ret i32 0
+}
 
-declare extern_weak i32 @pthread_join(i64, i8**)
+define weak i32 @pthread_join(i64, i8**) {
+  ret i32 0
+}
 
-declare extern_weak i32 @pthread_equal(i64, i64)
+define weak i32 @pthread_equal(i64, i64) {
+  ret i32 0
+}
 
-declare extern_weak i64 @pthread_self()
+define weak i64 @pthread_self() {
+  ret i64 0
+}
 
-declare extern_weak i32 @pthread_detach(i64)
+define weak i32 @pthread_detach(i64) {
+  ret i32 0
+}
 
-declare extern_weak i32 @pthread_cancel(i64)
+define weak i32 @pthread_cancel(i64) {
+  ret i32 0
+}
 
-declare extern_weak i32 @sched_yield()
+define weak i32 @sched_yield() {
+  ret i32 0
+}
 
-declare extern_weak i32 @pthread_mutex_lock(%union.pthread_mutex_t*)
+define weak i32 @pthread_mutex_lock(%union.pthread_mutex_t*) {
+  ret i32 0
+}
 
-declare extern_weak i32 @pthread_mutex_trylock(%union.pthread_mutex_t*)
+define weak i32 @pthread_mutex_trylock(%union.pthread_mutex_t*) {
+  ret i32 0
+}
 
-declare extern_weak i32 @pthread_mutex_timedlock(%union.pthread_mutex_t*, %struct.timespec*)
+define weak i32 @pthread_mutex_timedlock(%union.pthread_mutex_t*, %struct.timespec*) {
+  ret i32 0
+}
 
-declare extern_weak i32 @pthread_mutex_unlock(%union.pthread_mutex_t*)
+define weak i32 @pthread_mutex_unlock(%union.pthread_mutex_t*) {
+  ret i32 0
+}
 
-declare extern_weak i32 @pthread_mutex_init(%union.pthread_mutex_t*, %union.pthread_mutexattr_t*)
+define weak i32 @pthread_mutex_init(%union.pthread_mutex_t*, %union.pthread_mutexattr_t*) {
+  ret i32 0
+}
 
-declare extern_weak i32 @pthread_mutex_destroy(%union.pthread_mutex_t*)
+define weak i32 @pthread_mutex_destroy(%union.pthread_mutex_t*) {
+  ret i32 0
+}
 
-declare extern_weak i32 @pthread_cond_broadcast(%union.pthread_cond_t*)
+define weak i32 @pthread_cond_broadcast(%union.pthread_cond_t*) {
+  ret i32 0
+}
 
-declare extern_weak i32 @pthread_cond_signal(%union.pthread_cond_t*)
+define weak i32 @pthread_cond_signal(%union.pthread_cond_t*) {
+  ret i32 0
+}
 
-declare extern_weak i32 @pthread_cond_wait(%union.pthread_cond_t*, %union.pthread_mutex_t*)
+define weak i32 @pthread_cond_wait(%union.pthread_cond_t*, %union.pthread_mutex_t*) {
+  ret i32 0
+}
 
-declare extern_weak i32 @pthread_cond_timedwait(%union.pthread_cond_t*, %union.pthread_mutex_t*, %struct.timespec*)
+define weak i32 @pthread_cond_timedwait(%union.pthread_cond_t*, %union.pthread_mutex_t*, %struct.timespec*) {
+  ret i32 0
+}
 
-declare extern_weak i32 @pthread_cond_destroy(%union.pthread_cond_t*)
+define weak i32 @pthread_cond_destroy(%union.pthread_cond_t*) {
+  ret i32 0
+}
 
-declare extern_weak i32 @pthread_key_create(i32*, void (i8*)*)
+define weak i32 @pthread_key_create(i32*, void (i8*)*) {
+  ret i32 0
+}
 
-declare extern_weak i32 @pthread_key_delete(i32)
+define weak i32 @pthread_key_delete(i32) {
+  ret i32 0
+}
 
-declare extern_weak i32 @pthread_mutexattr_init(%union.pthread_mutexattr_t*)
+define weak i32 @pthread_mutexattr_init(%union.pthread_mutexattr_t*) {
+  ret i32 0
+}
 
-declare extern_weak i32 @pthread_mutexattr_settype(%union.pthread_mutexattr_t*, i32)
+define weak i32 @pthread_mutexattr_settype(%union.pthread_mutexattr_t*, i32) {
+  ret i32 0
+}
 
-declare extern_weak i32 @pthread_mutexattr_destroy(%union.pthread_mutexattr_t*)
+define weak i32 @pthread_mutexattr_destroy(%union.pthread_mutexattr_t*) {
+  ret i32 0
+}
diff --git a/test/Transforms/GVN/2009-03-10-PREOnVoid.ll b/test/Transforms/GVN/2009-03-10-PREOnVoid.ll
index 89d6a5f982..fd31fce59a 100644
--- a/test/Transforms/GVN/2009-03-10-PREOnVoid.ll
+++ b/test/Transforms/GVN/2009-03-10-PREOnVoid.ll
@@ -53,30 +53,58 @@ bb11:		; preds = %bb7, %bb5
 	unreachable
 }
 
-declare i32 @pthread_once(i32*, void ()*)
+define i32 @pthread_once(i32*, void ()*) {
+       ret i32 0
+}
 
-declare i8* @pthread_getspecific(i32)
+define i8* @pthread_getspecific(i32) {
+       ret i8* null
+}
 
-declare i32 @pthread_setspecific(i32, i8*)
+define i32 @pthread_setspecific(i32, i8*) {
+        ret i32 0
+}
 
-declare i32 @pthread_create(i32*, %struct.pthread_attr_t*, i8* (i8*)*, i8*)
+define i32 @pthread_create(i32*, %struct.pthread_attr_t*, i8* (i8*)*, i8*) {
+       ret i32 0
+}
 
-declare i32 @pthread_cancel(i32)
+define i32 @pthread_cancel(i32) {
+      ret i32 0
+}
 
-declare i32 @pthread_mutex_lock(%struct.pthread_mutex_t*)
+define i32 @pthread_mutex_lock(%struct.pthread_mutex_t*) {
+       ret i32 0
+}
 
-declare i32 @pthread_mutex_trylock(%struct.pthread_mutex_t*)
+define i32 @pthread_mutex_trylock(%struct.pthread_mutex_t*) {
+       ret i32 0
+}
 
-declare i32 @pthread_mutex_unlock(%struct.pthread_mutex_t*)
+define i32 @pthread_mutex_unlock(%struct.pthread_mutex_t*) {
+       ret i32 0
+}
 
-declare i32 @pthread_mutex_init(%struct.pthread_mutex_t*, %struct.__sched_param*)
+define i32 @pthread_mutex_init(%struct.pthread_mutex_t*, %struct.__sched_param*) {
+        ret i32 0
+}
 
-declare i32 @pthread_key_create(i32*, void (i8*)*)
+define i32 @pthread_key_create(i32*, void (i8*)*) {
+       ret i32 0
+}
 
-declare i32 @pthread_key_delete(i32)
+define i32 @pthread_key_delete(i32) {
+        ret i32 0
+}
 
-declare i32 @pthread_mutexattr_init(%struct.__sched_param*)
+define i32 @pthread_mutexattr_init(%struct.__sched_param*) {
+        ret i32 0
+}
 
-declare i32 @pthread_mutexattr_settype(%struct.__sched_param*, i32)
+define i32 @pthread_mutexattr_settype(%struct.__sched_param*, i32) {
+        ret i32 0
+}
 
-declare i32 @pthread_mutexattr_destroy(%struct.__sched_param*)
+define i32 @pthread_mutexattr_destroy(%struct.__sched_param*) {
+       ret i32 0
+}
diff --git a/test/Transforms/GlobalOpt/2009-02-15-BitcastAlias.ll b/test/Transforms/GlobalOpt/2009-02-15-BitcastAlias.ll
index a1b69efe1a..d6a565ad10 100644
--- a/test/Transforms/GlobalOpt/2009-02-15-BitcastAlias.ll
+++ b/test/Transforms/GlobalOpt/2009-02-15-BitcastAlias.ll
@@ -1,6 +1,6 @@
 ; RUN: opt < %s -globalopt
 
-@g = external global i32
+@g = global i32 0
 
 @a = alias bitcast (i32* @g to i8*)
 
diff --git a/test/Transforms/GlobalOpt/alias-resolve.ll b/test/Transforms/GlobalOpt/alias-resolve.ll
index 5e229b9426..64e3d88af8 100644
--- a/test/Transforms/GlobalOpt/alias-resolve.ll
+++ b/test/Transforms/GlobalOpt/alias-resolve.ll
@@ -9,8 +9,10 @@
 @bar1  = alias void ()* @bar2
 ; CHECK: @bar1 = alias void ()* @bar2
 
-declare void @bar2()
-; CHECK: declare void @bar2()
+define void @bar2() {
+  ret void
+}
+; CHECK: define void @bar2()
 
 define void @baz() {
 entry:
diff --git a/test/Transforms/InstCombine/2007-09-10-AliasConstFold.ll b/test/Transforms/InstCombine/2007-09-10-AliasConstFold.ll
index c27fe0ab6a..7f9bd9e40d 100644
--- a/test/Transforms/InstCombine/2007-09-10-AliasConstFold.ll
+++ b/test/Transforms/InstCombine/2007-09-10-AliasConstFold.ll
@@ -3,7 +3,9 @@
 
 @__gthrw_pthread_cancel = alias weak i32 (i32)* @pthread_cancel		; <i32 (i32)*> [#uses=1]
 @__gthread_active_ptr.5335 = internal constant i8* bitcast (i32 (i32)* @__gthrw_pthread_cancel to i8*)		; <i8**> [#uses=1]
-declare extern_weak i32 @pthread_cancel(i32)
+define weak i32 @pthread_cancel(i32) {
+       ret i32 0
+}
 
 define i1 @__gthread_active_p() {
 entry:
diff --git a/test/Transforms/InstCombine/2007-09-17-AliasConstFold2.ll b/test/Transforms/InstCombine/2007-09-17-AliasConstFold2.ll
index 23ee12ba75..c7cef752dc 100644
--- a/test/Transforms/InstCombine/2007-09-17-AliasConstFold2.ll
+++ b/test/Transforms/InstCombine/2007-09-17-AliasConstFold2.ll
@@ -3,7 +3,9 @@
 
 @A = alias weak void ()* @B		; <void ()*> [#uses=1]
 
-declare extern_weak void @B()
+define weak void @B() {
+       ret void
+}
 
 define i32 @active() {
 entry:
diff --git a/test/Transforms/MetaRenamer/metarenamer.ll b/test/Transforms/MetaRenamer/metarenamer.ll
index 4020e10450..6297af62ff 100644
--- a/test/Transforms/MetaRenamer/metarenamer.ll
+++ b/test/Transforms/MetaRenamer/metarenamer.ll
@@ -14,7 +14,9 @@ target triple = "x86_64-pc-linux-gnu"
 
 @func_7_xxx = alias weak i32 (...)* @aliased_func_7_xxx
 
-declare i32 @aliased_func_7_xxx(...)
+define i32 @aliased_func_7_xxx(...) {
+  ret i32 0
+}
 
 define i32 @func_3_xxx() nounwind uwtable ssp {
   ret i32 3
diff --git a/test/Verifier/alias.ll b/test/Verifier/alias.ll
new file mode 100644
index 0000000000..e3636bc701
--- /dev/null
+++ b/test/Verifier/alias.ll
@@ -0,0 +1,12 @@
+; RUN:  not llvm-as %s -o /dev/null 2>&1 | FileCheck %s
+
+
+declare void @f()
+@fa = alias void ()* @f
+; CHECK: Alias must point to a definition
+; CHECK-NEXT: @fa
+
+@g = external global i32
+@ga = alias i32* @g
+; CHECK: Alias must point to a definition
+; CHECK-NEXT: @ga