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

Issues addressed since original review:
- Avoid bug in regalloc greedy/machine verifier when forwarding to use
  in an instruction that re-defines the same virtual register.
- Fixed bug when forwarding to use in EarlyClobber instruction slot.
- Fixed incorrect forwarding to register definitions that showed up in
  explicit_uses() iterator (e.g. in INLINEASM).
- Moved removal of dead instructions found by
  LiveIntervals::shrinkToUses() outside of loop iterating over
  instructions to avoid instructions being deleted while pointed to by
  iterator.
- Fixed ARMLoadStoreOptimizer bug exposed by this change in r311907.
- The pass no longer forwards COPYs to physical register uses, since
  doing so can break code that implicitly relies on the physical
  register number of the use.
- The pass no longer forwards COPYs to undef uses, since doing so
  can break the machine verifier by creating LiveRanges that don't
  end on a use (since the undef operand is not considered a use).

  [MachineCopyPropagation] Extend pass to do COPY source forwarding

  This change extends MachineCopyPropagation to do COPY source forwarding.

  This change also extends the MachineCopyPropagation pass to be able to
  be run during register allocation, after physical registers have been
  assigned, but before the virtual registers have been re-written, which
  allows it to remove virtual register COPY LiveIntervals that become dead
  through the forwarding of all of their uses.

llvm-svn: 314729

1 files changed, 8 insertions, 8 deletions

diff --git a/llvm/test/CodeGen/AMDGPU/ret.ll b/llvm/test/CodeGen/AMDGPU/ret.ll
index 831c71dff79..2d673a9b0cd 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: 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-DAG: v_mov_b32_e32 v1, v0
+; GCN-DAG: exp mrt0 v0, v0, v0, v0 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 @@ bb:
 }
 
 ; GCN-LABEL: {{^}}both:
-; 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: 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_mov_b32 s2, s3
 ; GCN: s_waitcnt expcnt(0)
+; GCN: v_add_f32_e32 v0, 1.0, v0
+; GCN-DAG: s_add_i32 s0, s3, 2
+; GCN-DAG: s_mov_b32 s2, s3
 ; 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: