AMDGPU: Unify divergent function exits.

StructurizeCFG can't handle cases with multiple
returns creating regions with multiple exits.
Create a copy of UnifyFunctionExitNodes that only
unifies exit nodes that skips exit nodes
with uniform branch sources.

llvm-svn: 298729
diff --git a/llvm/test/CodeGen/AMDGPU/si-lower-control-flow-unreachable-block.ll b/llvm/test/CodeGen/AMDGPU/si-lower-control-flow-unreachable-block.ll
index 89c1eeb..cb010cf 100644
--- a/llvm/test/CodeGen/AMDGPU/si-lower-control-flow-unreachable-block.ll
+++ b/llvm/test/CodeGen/AMDGPU/si-lower-control-flow-unreachable-block.ll
@@ -4,16 +4,17 @@
 ; GCN: v_cmp_eq_u32
 ; GCN: s_and_saveexec_b64
 ; GCN: s_xor_b64
-; GCN: ; mask branch [[RET:BB[0-9]+]]
-; GCN: s_branch [[UNREACHABLE:BB[0-9]+_[0-9]+]]
+; GCN: ; mask branch [[RET:BB[0-9]+_[0-9]+]]
 
-; GCN: [[RET]]
-; GCN: s_or_b64 exec, exec
+; GCN-NEXT: BB{{[0-9]+_[0-9]+}}: ; %unreachable
+; GCN: ds_write_b32
+; GCN: ; divergent unreachable
+; GCN: s_waitcnt
+
+; GCN-NEXT: [[RET]]: ; %UnifiedReturnBlock
+; GCN-NEXT: s_or_b64 exec, exec
 ; GCN: s_endpgm
 
-; GCN: [[UNREACHABLE]]:
-; GCN: ds_write_b32
-; GCN: s_waitcnt
 define amdgpu_kernel void @lower_control_flow_unreachable_terminator() #0 {
 bb:
   %tmp15 = tail call i32 @llvm.amdgcn.workitem.id.y()
@@ -29,18 +30,19 @@
 }
 
 ; GCN-LABEL: {{^}}lower_control_flow_unreachable_terminator_swap_block_order:
-; GCN: v_cmp_eq_u32
+; GCN: v_cmp_ne_u32
 ; GCN: s_and_saveexec_b64
 ; GCN: s_xor_b64
-; GCN: ; mask branch [[UNREACHABLE:BB[0-9]+_[0-9]+]]
+; GCN: ; mask branch [[RETURN:BB[0-9]+_[0-9]+]]
 
-; GCN-NEXT: ; %ret
-; GCN-NEXT: s_endpgm
-
-; GCN-NEXT: [[UNREACHABLE]]:
-; GCN-NEXT: s_or_b64 exec, exec
+; GCN-NEXT: {{^BB[0-9]+_[0-9]+}}: ; %unreachable
 ; GCN: ds_write_b32
+; GCN: ; divergent unreachable
 ; GCN: s_waitcnt
+
+; GCN: [[RETURN]]:
+; GCN-NEXT: s_or_b64 exec, exec
+; GCN-NEXT: s_endpgm
 define amdgpu_kernel void @lower_control_flow_unreachable_terminator_swap_block_order() #0 {
 bb:
   %tmp15 = tail call i32 @llvm.amdgcn.workitem.id.y()
@@ -55,7 +57,29 @@
   unreachable
 }
 
-; Function Attrs: nounwind readnone
+; GCN-LABEL: {{^}}uniform_lower_control_flow_unreachable_terminator:
+; GCN: s_cmp_lg_u32
+; GCN: s_cbranch_scc0 [[UNREACHABLE:BB[0-9]+_[0-9]+]]
+
+; GCN-NEXT: BB#{{[0-9]+}}: ; %ret
+; GCN-NEXT: s_endpgm
+
+; GCN: [[UNREACHABLE]]:
+; GCN: ds_write_b32
+; GCN: s_waitcnt
+define amdgpu_kernel void @uniform_lower_control_flow_unreachable_terminator(i32 %arg0) #0 {
+bb:
+  %tmp63 = icmp eq i32 %arg0, 32
+  br i1 %tmp63, label %unreachable, label %ret
+
+unreachable:
+  store volatile i32 0, i32 addrspace(3)* undef, align 4
+  unreachable
+
+ret:
+  ret void
+}
+
 declare i32 @llvm.amdgcn.workitem.id.y() #1
 
 attributes #0 = { nounwind }