MergeFunctions: Impose a total order on the replacement of functions

We don't want to replace function A by Function B in one module and Function B
by Function A in another module.

If these functions are marked with linkonce_odr we would end up with a function
stub calling B in one module and a function stub calling A in another module. If
the linker decides to pick these two we will have two stubs calling each other.

rdar://21265586

llvm-svn: 239367

2 files changed, 34 insertions, 4 deletions

diff --git a/llvm/test/Transforms/MergeFunc/call-and-invoke-with-ranges.ll b/llvm/test/Transforms/MergeFunc/call-and-invoke-with-ranges.ll
index b2083cb5c70..99eba5e2809 100644
--- a/llvm/test/Transforms/MergeFunc/call-and-invoke-with-ranges.ll
+++ b/llvm/test/Transforms/MergeFunc/call-and-invoke-with-ranges.ll
@@ -63,16 +63,16 @@ lpad:
   resume { i8*, i32 } zeroinitializer
 }
 
-define i8 @call_same_range() {
-; CHECK-LABEL: @call_same_range
+define i8 @call_with_same_range() {
+; CHECK-LABEL: @call_with_same_range
 ; CHECK: tail call i8 @call_with_range
   bitcast i8 0 to i8
   %out = call i8 @dummy(), !range !0
   ret i8 %out
 }
 
-define i8 @invoke_same_range() {
-; CHECK-LABEL: @invoke_same_range()
+define i8 @invoke_with_same_range() {
+; CHECK-LABEL: @invoke_with_same_range()
 ; CHECK: tail call i8 @invoke_with_range()
   %out = invoke i8 @dummy() to label %next unwind label %lpad, !range !0
 
diff --git a/llvm/test/Transforms/MergeFunc/linkonce_odr.ll b/llvm/test/Transforms/MergeFunc/linkonce_odr.ll
new file mode 100644
index 00000000000..1ad0d727f83
--- /dev/null
+++ b/llvm/test/Transforms/MergeFunc/linkonce_odr.ll
@@ -0,0 +1,30 @@
+; RUN: opt -S -mergefunc < %s | FileCheck %s
+
+; Replacments should be totally ordered on the function name.
+; If we don't do this we  can end up with one module defining a thunk for @funA
+; and another module defining a thunk for @funB.
+;
+; The problem with this is that the linker could then choose these two stubs
+; each of the two modules and we end up with two stubs calling each other.
+
+; CHECK-LABEL: define linkonce_odr i32 @funA
+; CHECK-NEXT:    add
+; CHECK:         ret
+
+; CHECK-LABEL: define linkonce_odr i32 @funB
+; CHECK-NEXT:    tail call i32 @funA(i32 %0, i32 %1)
+; CHECK-NEXT:    ret
+
+define linkonce_odr i32 @funB(i32 %x, i32 %y) {
+  %sum = add i32 %x, %y
+  %sum2 = add i32 %x, %sum
+  %sum3 = add i32 %x, %sum2
+  ret i32 %sum3
+}
+
+define linkonce_odr i32 @funA(i32 %x, i32 %y) {
+  %sum = add i32 %x, %y
+  %sum2 = add i32 %x, %sum
+  %sum3 = add i32 %x, %sum2
+  ret i32 %sum3
+}