From 65528f29913a541f3d250dbee2d93a3b1db68e4d Mon Sep 17 00:00:00 2001
From: Geoff Berry <gberry@codeaurora.org>
Date: Fri, 1 Sep 2017 14:27:20 +0000
Subject: Re-enable "[MachineCopyPropagation] Extend pass to do COPY source
 forwarding"

Issues addressed since original review:
- 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: 312328
---
 llvm/lib/CodeGen/CodeGen.cpp | 1 +
 1 file changed, 1 insertion(+)

(limited to 'llvm/lib/CodeGen/CodeGen.cpp')

diff --git a/llvm/lib/CodeGen/CodeGen.cpp b/llvm/lib/CodeGen/CodeGen.cpp
index b7fd45a3f6a..c92b45a752e 100644
--- a/llvm/lib/CodeGen/CodeGen.cpp
+++ b/llvm/lib/CodeGen/CodeGen.cpp
@@ -54,6 +54,7 @@ void llvm::initializeCodeGen(PassRegistry &Registry) {
   initializeMachineCSEPass(Registry);
   initializeMachineCombinerPass(Registry);
   initializeMachineCopyPropagationPass(Registry);
+  initializeMachineCopyPropagationPreRegRewritePass(Registry);
   initializeMachineDominatorTreePass(Registry);
   initializeMachineFunctionPrinterPassPass(Registry);
   initializeMachineLICMPass(Registry);
-- 
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