Don't merge two constants if we care about the address of both.

This fixes the original testcase in PR8927. It also causes a clang
binary built with a patched clang to increase in size by 0.21%.

We can probably get some of the size back by writing a pass that
detects that a global never has its pointer compared and adds
unnamed_addr to it (maybe extend global opt). It is also possible that
there are some other cases clang could add unnamed_addr to.

I will investigate extending globalopt next.

llvm-svn: 123584

1 files changed, 26 insertions, 0 deletions

diff --git a/llvm/test/Transforms/ConstantMerge/merge-both.ll b/llvm/test/Transforms/ConstantMerge/merge-both.ll
new file mode 100644
index 00000000000..0282f464aee
--- /dev/null
+++ b/llvm/test/Transforms/ConstantMerge/merge-both.ll
@@ -0,0 +1,26 @@
+; RUN: opt -constmerge %s -S -o - | FileCheck %s
+; Test that in one run var3 is merged into var2 and var1 into var4.
+
+declare void @zed(%struct.foobar*, %struct.foobar*)
+
+%struct.foobar = type { i32 }
+
+@var1 = internal constant %struct.foobar { i32 2 }
+@var2 = unnamed_addr constant %struct.foobar { i32 2 }
+@var3 = internal constant %struct.foobar { i32 2 }
+@var4 = unnamed_addr constant %struct.foobar { i32 2 }
+
+; CHECK:      %struct.foobar = type { i32 }
+; CHECK-NOT: @
+; CHECK: @var2 = constant %struct.foobar { i32 2 }
+; CHECK-NEXT: @var4 = constant %struct.foobar { i32 2 }
+; CHECK-NOT: @
+; CHECK: declare void @zed(%struct.foobar*, %struct.foobar*)
+
+define i32 @main() {
+entry:
+  call void @zed(%struct.foobar* @var1, %struct.foobar* @var2)
+  call void @zed(%struct.foobar* @var3, %struct.foobar* @var4)
+  ret i32 0
+}
+