Do not use named function labels if function names are not unique.

test/cmdlineTests/yul_function_name_clashes/args

@@ -0,0 +1 @@
+--strict-assembly --debug-info none

test/cmdlineTests/yul_function_name_clashes/err

@@ -0,0 +1 @@
+Warning: Yul is still experimental. Please use the output with care.

test/cmdlineTests/yul_function_name_clashes/input.yul

@@ -0,0 +1,17 @@
+object "object" {
+    code {
+        let a
+        let b
+        {
+            function z() -> y
+            { y := calldataload(0) }
+            a := z()
+        }
+        {
+            function z() -> y
+            { y := calldataload(0x20) }
+            b := z()
+        }
+        sstore(a, b)
+    }
+}

test/cmdlineTests/yul_function_name_clashes/output

@@ -0,0 +1,66 @@
+
+======= yul_function_name_clashes/input.yul (EVM) =======
+
+Pretty printed source:
+object "object" {
+    code {
+        let a
+        let b
+        {
+            function z() -> y
+            { y := calldataload(0) }
+            a := z()
+        }
+        {
+            function z() -> y
+            { y := calldataload(0x20) }
+            b := z()
+        }
+        sstore(a, b)
+    }
+}
+
+
+Binary representation:
+600080600f565b60008035905090565b60156006565b91506025565b6000602035905090565b602b601b565b90508082555050
+
+Text representation:
+  0x00
+  dup1
+  jump(tag_2)
+tag_1:
+  0x00
+  dup1
+  calldataload
+  swap1
+  pop
+  swap1
+  jump	// out
+tag_2:
+  tag_4
+  tag_1
+  jump	// in
+tag_4:
+  swap2
+  pop
+  jump(tag_6)
+tag_5:
+  0x00
+  0x20
+  calldataload
+  swap1
+  pop
+  swap1
+  jump	// out
+tag_6:
+  tag_8
+  tag_5
+  jump	// in
+tag_8:
+  swap1
+  pop
+  dup1
+  dup3
+  sstore
+  pop
+  pop