Error if we see an alias to a declaration.

In ELF and COFF an alias is just another offset in a section. There is no way
to represent an alias to something in another file.

In MachO, the spec has the N_INDR type which should allow for exactly that, but
is not currently implemented. Given that it is specified but not implemented,
we error in codegen to avoid miscompiling but don't reject aliases to
declarations in the verifier to leave the option open of implementing it.

In the past we have used alias to declarations as a way of implementing
weakref, which is why it exists in some old tests which this patch updates.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194705 91177308-0d34-0410-b5e6-96231b3b80d8

10 files changed, 75 insertions, 26 deletions

diff --git a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 44a8316723..308b0e091a 100644
--- a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -949,6 +949,11 @@ 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");
+      }
+
       MCSymbol *Target = getSymbol(GV);
 
       if (I->hasExternalLinkage() || !MAI->getWeakRefDirective())
diff --git a/test/CodeGen/ARM/aliases.ll b/test/CodeGen/ARM/aliases.ll
index 4147bd0be0..f55ae10b24 100644
--- a/test/CodeGen/ARM/aliases.ll
+++ b/test/CodeGen/ARM/aliases.ll
@@ -16,13 +16,15 @@
 ; CHECK: .globl	A
 ; CHECK: A = bar
 
-@bar = external global i32
+@bar = global i32 42
 @foo1 = alias i32* @bar
 @foo2 = alias i32* @bar
 
 %FunTy = type i32()
 
-declare i32 @foo_f()
+define i32 @foo_f() {
+  ret i32 0
+}
 @bar_f = alias weak %FunTy* @foo_f
 
 @bar_i = alias internal i32* @bar
diff --git a/test/CodeGen/Generic/2009-03-17-LSR-APInt.ll b/test/CodeGen/Generic/2009-03-17-LSR-APInt.ll
index 6281ada73f..3f17ce1e0b 100644
--- a/test/CodeGen/Generic/2009-03-17-LSR-APInt.ll
+++ b/test/CodeGen/Generic/2009-03-17-LSR-APInt.ll
@@ -63,30 +63,58 @@ bb47:		; preds = %bb46, %bb44
 	br label %bb44
 }
 
-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(i64*, %struct.pthread_attr_t*, i8* (i8*)*, i8*)
+define i32 @pthread_create(i64*, %struct.pthread_attr_t*, i8* (i8*)*, i8*) {
+  ret i32 0
+}
 
-declare i32 @pthread_cancel(i64)
+define i32 @pthread_cancel(i64) {
+  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.Alignment*)
+define i32 @pthread_mutex_init(%struct.pthread_mutex_t*, %struct.Alignment*) {
+  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.Alignment*)
+define i32 @pthread_mutexattr_init(%struct.Alignment*) {
+  ret i32 0
+}
 
-declare i32 @pthread_mutexattr_settype(%struct.Alignment*, i32)
+define i32 @pthread_mutexattr_settype(%struct.Alignment*, i32) {
+  ret i32 0
+}
 
-declare i32 @pthread_mutexattr_destroy(%struct.Alignment*)
+define i32 @pthread_mutexattr_destroy(%struct.Alignment*) {
+  ret i32 0
+}
diff --git a/test/CodeGen/PowerPC/mcm-9.ll b/test/CodeGen/PowerPC/mcm-9.ll
index e587f61eaf..7906b6abea 100644
--- a/test/CodeGen/PowerPC/mcm-9.ll
+++ b/test/CodeGen/PowerPC/mcm-9.ll
@@ -7,8 +7,7 @@
 target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-f128:128:128-v128:128:128-n32:64"
 target triple = "powerpc64-unknown-linux-gnu"
 
-@ei = external global i32
-@a = alias i32* @ei
+@a = external global i32
 
 define signext i32 @test_external() nounwind {
 entry:
diff --git a/test/CodeGen/X86/2007-09-06-ExtWeakAliasee.ll b/test/CodeGen/X86/2007-09-06-ExtWeakAliasee.ll
index c5d2a46f92..7e37ef5c40 100644
--- a/test/CodeGen/X86/2007-09-06-ExtWeakAliasee.ll
+++ b/test/CodeGen/X86/2007-09-06-ExtWeakAliasee.ll
@@ -1,4 +1,6 @@
 ; RUN: llc < %s -march=x86 | grep weak | count 2
 @__gthrw_pthread_once = alias weak i32 (i32*, void ()*)* @pthread_once		; <i32 (i32*, void ()*)*> [#uses=0]
 
-declare extern_weak i32 @pthread_once(i32*, void ()*)
+define weak i32 @pthread_once(i32*, void ()*) {
+  ret i32 0
+}
diff --git a/test/CodeGen/X86/2008-03-14-SpillerCrash.ll b/test/CodeGen/X86/2008-03-14-SpillerCrash.ll
index 8946415108..18b3714f85 100644
--- a/test/CodeGen/X86/2008-03-14-SpillerCrash.ll
+++ b/test/CodeGen/X86/2008-03-14-SpillerCrash.ll
@@ -45,4 +45,6 @@ bb383:		; preds = %bb374.us, %bb311.split
 	ret i64 0
 }
 
-declare i64 @__wcstoll_l(i32*, i32**, i32, %struct.__locale_struct*) nounwind 
+define i64 @__wcstoll_l(i32*, i32**, i32, %struct.__locale_struct*) nounwind {
+  ret i64 0
+}
diff --git a/test/CodeGen/X86/alias-error.ll b/test/CodeGen/X86/alias-error.ll
new file mode 100644
index 0000000000..89b0876a83
--- /dev/null
+++ b/test/CodeGen/X86/alias-error.ll
@@ -0,0 +1,5 @@
+; RUN: not llc < %s -mtriple=i686-pc-linux-gnu %s 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/CodeGen/X86/aliases.ll b/test/CodeGen/X86/aliases.ll
index 025dcfedb6..d0a262d390 100644
--- a/test/CodeGen/X86/aliases.ll
+++ b/test/CodeGen/X86/aliases.ll
@@ -1,6 +1,6 @@
 ; RUN: llc < %s -mtriple=i686-pc-linux-gnu -asm-verbose=false | FileCheck %s
 
-@bar = external global i32
+@bar = global i32 42
 
 ; CHECK-DAG: .globl	foo1
 @foo1 = alias i32* @bar
@@ -10,7 +10,9 @@
 
 %FunTy = type i32()
 
-declare i32 @foo_f()
+define i32 @foo_f() {
+  ret i32 0
+}
 ; CHECK-DAG: .weak	bar_f
 @bar_f = alias weak %FunTy* @foo_f
 
diff --git a/test/CodeGen/X86/x86-64-pic-10.ll b/test/CodeGen/X86/x86-64-pic-10.ll
index 3ec172b2b6..da8082b925 100644
--- a/test/CodeGen/X86/x86-64-pic-10.ll
+++ b/test/CodeGen/X86/x86-64-pic-10.ll
@@ -9,4 +9,6 @@ entry:
         ret void
 }
 
-declare extern_weak i32 @f()
+define weak i32 @f() {
+  ret i32 42
+}
diff --git a/test/CodeGen/XCore/aliases.ll b/test/CodeGen/XCore/aliases.ll
index d4da63c5d9..b7ad416968 100644
--- a/test/CodeGen/XCore/aliases.ll
+++ b/test/CodeGen/XCore/aliases.ll
@@ -1,7 +1,9 @@
 ; RUN: llc < %s -march=xcore | FileCheck %s
-declare void @a_val() nounwind
-@b_val = external constant i32, section ".cp.rodata"
-@c_val = external global i32
+define void @a_val() nounwind {
+  ret void
+}
+@b_val = constant i32 42, section ".cp.rodata"
+@c_val = global i32 42
 
 @a = alias void ()* @a_val
 @b = alias i32* @b_val