[Beignet] [PATCH 2/2] GBE: Fix one DAG analysis issue and enable multiple round phi copy elimination.

[Zhigang Gong]

Even if one value is killed in current BB, we still need to
pass predecessor's definition into this BB. Otherwise, we will
miss one definition.

BB0:
  MOV %foo, %src0

BB1:
  MUL %foo, %src1, %f00
  ...
  BR BB1

In the above case, both BB1 and BB0 are the predecessors of BB1.
When pass the definition of %foo in BB0 to BB1, the previous implementation
will ignore it because %foo is killed in BB1, this is a bug.
This patch fixes it. And thus we can enable multiple round
phi copy elimination safely.

Signed-off-by: Zhigang Gong <zhigang.gong at intel.com>
---
 backend/src/ir/value.cpp              | 2 +-
 backend/src/llvm/llvm_gen_backend.cpp | 1 -
 2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/backend/src/ir/value.cpp b/backend/src/ir/value.cpp
index 75a100f..7b54763 100644
--- a/backend/src/ir/value.cpp
+++ b/backend/src/ir/value.cpp
@@ -242,7 +242,7 @@ namespace ir {
         const BasicBlock &pbb = pred.bb;
         for (auto reg : curr.liveOut) {
           if (pred.inLiveOut(reg) == false) continue;
-          if (curr.inVarKill(reg) == true) continue;
+          if (curr.inVarKill(reg) == true && curr.inUpwardUsed(reg) == false) continue;
           RegDefSet &currSet = this->getDefSet(&bb, reg);
           RegDefSet &predSet = this->getDefSet(&pbb, reg);
 
diff --git a/backend/src/llvm/llvm_gen_backend.cpp b/backend/src/llvm/llvm_gen_backend.cpp
index 1d09727..4ac2c53 100644
--- a/backend/src/llvm/llvm_gen_backend.cpp
+++ b/backend/src/llvm/llvm_gen_backend.cpp
@@ -2403,7 +2403,6 @@ namespace gbe
       } else
         break;
 
-      break;
       nextRedundant->clear();
       replacedRegs.clear();
       revReplacedRegs.clear();
-- 
1.9.1