GBE: Fix one DAG analysis issue and enable multiple round phi copy elimination.

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@intel.com>

2 files changed, 1 insertions, 2 deletions

diff --git a/backend/src/ir/value.cpp b/backend/src/ir/value.cpp
index 72caa133..027c8de2 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 1d097277..4ac2c53a 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();