Revert "Re-enable "[MachineCopyPropagation] Extend pass to do COPY source forwarding""

This reverts commit r314729.

Another bug has been encountered in an out-of-tree target reported by Quentin.

llvm-svn: 314814
diff --git a/llvm/test/CodeGen/AMDGPU/ret.ll b/llvm/test/CodeGen/AMDGPU/ret.ll
index 2d673a9..831c71d 100644
--- a/llvm/test/CodeGen/AMDGPU/ret.ll
+++ b/llvm/test/CodeGen/AMDGPU/ret.ll
@@ -2,10 +2,10 @@
 ; RUN: llc -march=amdgcn -mcpu=tonga -verify-machineinstrs < %s | FileCheck -check-prefix=GCN %s
 
 ; GCN-LABEL: {{^}}vgpr:
-; GCN-DAG: v_mov_b32_e32 v1, v0
-; GCN-DAG: exp mrt0 v0, v0, v0, v0 done vm
+; GCN: v_mov_b32_e32 v1, v0
+; GCN-DAG: v_add_f32_e32 v0, 1.0, v1
+; GCN-DAG: exp mrt0 v1, v1, v1, v1 done vm
 ; GCN: s_waitcnt expcnt(0)
-; GCN: v_add_f32_e32 v0, 1.0, v0
 ; GCN-NOT: s_endpgm
 define amdgpu_vs { float, float } @vgpr([9 x <16 x i8>] addrspace(2)* byval %arg, i32 inreg %arg1, i32 inreg %arg2, float %arg3) #0 {
 bb:
@@ -204,13 +204,13 @@
 }
 
 ; GCN-LABEL: {{^}}both:
-; GCN-DAG: exp mrt0 v0, v0, v0, v0 done vm
-; GCN-DAG: v_mov_b32_e32 v1, v0
-; GCN-DAG: s_mov_b32 s1, s2
-; GCN: s_waitcnt expcnt(0)
-; GCN: v_add_f32_e32 v0, 1.0, v0
+; GCN: v_mov_b32_e32 v1, v0
+; GCN-DAG: exp mrt0 v1, v1, v1, v1 done vm
+; GCN-DAG: v_add_f32_e32 v0, 1.0, v1
 ; GCN-DAG: s_add_i32 s0, s3, 2
-; GCN-DAG: s_mov_b32 s2, s3
+; GCN-DAG: s_mov_b32 s1, s2
+; GCN: s_mov_b32 s2, s3
+; GCN: s_waitcnt expcnt(0)
 ; GCN-NOT: s_endpgm
 define amdgpu_vs { float, i32, float, i32, i32 } @both([9 x <16 x i8>] addrspace(2)* byval %arg, i32 inreg %arg1, i32 inreg %arg2, float %arg3) #0 {
 bb: