GBE: optimize the CMP instruction.

If the dst bool value is not in the liveIn set, then we don't need
to care about those inactive lanes as they don't hold any active data.

Signed-off-by: Zhigang Gong <zhigang.gong@intel.com>
Reviewed-by: "Yang, Rong R" <rong.r.yang@intel.com>

diff --git a/backend/src/backend/gen_insn_selection.cpp b/backend/src/backend/gen_insn_selection.cpp
index 6cccc11..74a1e70 100644 (file)
--- a/backend/src/backend/gen_insn_selection.cpp
+++ b/backend/src/backend/gen_insn_selection.cpp
@@ -2519,20 +2519,32 @@ namespace gbe
       const Opcode opcode = insn.getOpcode();
       const Type type = insn.getType();
       const Register dst = insn.getDst(0);
-      const Register tmpDst = sel.reg(FAMILY_BOOL);
+      Register tmpDst;
+
+      const ir::BasicBlock *insnBlock = insn.getParent();
+      const ir::Liveness &liveness = sel.ctx.getLiveness();
+      const ir::Liveness::UEVar &livein = liveness.getLiveIn(insnBlock);
+      if (!livein.contains(dst))
+        tmpDst = dst;
+      else
+        tmpDst = sel.reg(FAMILY_BOOL);
 
       // Limit the compare to the active lanes. Use the same compare as for f0.0
       sel.push();
         const LabelIndex label = insn.getParent()->getLabelIndex();
         const GenRegister blockip = sel.selReg(ocl::blockip, TYPE_U16);
         const GenRegister labelReg = GenRegister::immuw(label);
+
         sel.curr.predicate = GEN_PREDICATE_NONE;
         sel.curr.physicalFlag = 0;
         sel.curr.flagIndex = uint16_t(tmpDst);
-        sel.CMP(GEN_CONDITIONAL_G, blockip, labelReg);
-        sel.curr.execWidth = 1;
-        sel.AND(sel.selReg(dst, TYPE_BOOL), sel.selReg(dst, TYPE_BOOL), sel.selReg(tmpDst, TYPE_BOOL));
-        sel.XOR(sel.selReg(tmpDst, TYPE_BOOL), sel.selReg(tmpDst, TYPE_BOOL), GenRegister::immuw(0xFFFF));
+        if (tmpDst != dst) {
+          sel.CMP(GEN_CONDITIONAL_G, blockip, labelReg);
+          sel.curr.execWidth = 1;
+          sel.AND(sel.selReg(dst, TYPE_BOOL), sel.selReg(dst, TYPE_BOOL), sel.selReg(tmpDst, TYPE_BOOL));
+          sel.XOR(sel.selReg(tmpDst, TYPE_BOOL), sel.selReg(tmpDst, TYPE_BOOL), GenRegister::immuw(0xFFFF));
+        } else
+          sel.CMP(GEN_CONDITIONAL_LE, blockip, labelReg);
       sel.pop();
 
       // Look for immediate values for the right source
@@ -2570,11 +2582,13 @@ namespace gbe
         } else
           sel.CMP(getGenCompare(opcode), src0, src1);
       sel.pop();
-      sel.push();
-        sel.curr.predicate = GEN_PREDICATE_NONE;
-        sel.curr.execWidth = 1;
-        sel.OR(sel.selReg(dst, TYPE_U16), sel.selReg(dst, TYPE_U16), sel.selReg(tmpDst, TYPE_U16));
-      sel.pop();
+      if (tmpDst != dst) {
+        sel.push();
+          sel.curr.predicate = GEN_PREDICATE_NONE;
+          sel.curr.execWidth = 1;
+          sel.OR(sel.selReg(dst, TYPE_U16), sel.selReg(dst, TYPE_U16), sel.selReg(tmpDst, TYPE_U16));
+        sel.pop();
+      }
       return true;
     }
   };