Don't load values out of global constants with weak

linkage: the value may be replaced with something
different at link time.  (Frontends that want to
allow values to be loaded out of weak constants can
give their constants weak_odr linkage).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@67407 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 50 insertions, 0 deletions

diff --git a/test/Feature/weak_constant.ll b/test/Feature/weak_constant.ll
new file mode 100644
index 0000000000..d27adfefa5
--- /dev/null
+++ b/test/Feature/weak_constant.ll
@@ -0,0 +1,38 @@
+; RUN: llvm-as < %s | opt -std-compile-opts | llvm-dis > %t
+; RUN:   grep undef %t | count 1
+; RUN:   grep 5 %t | count 1
+; RUN:   grep 7 %t | count 1
+; RUN:   grep 9 %t | count 1
+
+	type { i32, i32 }		; type %0
+@a = weak constant i32 undef		; <i32*> [#uses=1]
+@b = weak constant i32 5		; <i32*> [#uses=1]
+@c = weak constant %0 { i32 7, i32 9 }		; <%0*> [#uses=1]
+
+define i32 @la() {
+	%v = load i32* @a		; <i32> [#uses=1]
+	ret i32 %v
+}
+
+define i32 @lb() {
+	%v = load i32* @b		; <i32> [#uses=1]
+	ret i32 %v
+}
+
+define i32 @lc() {
+	%g = getelementptr %0* @c, i32 0, i32 0		; <i32*> [#uses=1]
+	%u = load i32* %g		; <i32> [#uses=1]
+	%h = getelementptr %0* @c, i32 0, i32 1		; <i32*> [#uses=1]
+	%v = load i32* %h		; <i32> [#uses=1]
+	%r = add i32 %u, %v
+	ret i32 %r
+}
+
+define i32 @f() {
+	%u = call i32 @la()		; <i32> [#uses=1]
+	%v = call i32 @lb()		; <i32> [#uses=1]
+	%w = call i32 @lc()		; <i32> [#uses=1]
+	%r = add i32 %u, %v		; <i32> [#uses=1]
+	%s = add i32 %r, %w		; <i32> [#uses=1]
+	ret i32 %s
+}
diff --git a/test/FrontendC/weak_constant.c b/test/FrontendC/weak_constant.c
new file mode 100644
index 0000000000..53379482cb
--- /dev/null
+++ b/test/FrontendC/weak_constant.c
@@ -0,0 +1,12 @@
+// RUN: %llvmgcc -S %s -O1 -o - | grep {ret.*123}
+// Check for bug compatibility with gcc.
+
+const int x __attribute((weak)) = 123;
+
+int* f(void) {
+  return &x;
+}
+
+int g(void) {
+  return *f();
+}