[Beignet] [PATCH] GBE: fixed the out-of-range JMPI.

[Zhigang Gong]

For the conditional jump distance out of S15 range [-32768, 32767],
we need to use an inverted jmp followed by a add ip, ip, distance
to implement. A little hacky as we need to change the nop instruction
to add instruction manually.

There is an optimization method which we can insert a
ADD instruction on demand. But that will need some extra analysis
for all the branching instruction. And need to adjust the distance
for those branch instruction's start point and end point contains
this instruction.

After this patch, the luxrender's slg4 could render the scene "alloy"
correctly.

Signed-off-by: Zhigang Gong <zhigang.gong at intel.com>
---
 backend/src/backend/gen_context.cpp |    6 +++---
 backend/src/backend/gen_encoder.cpp |   30 +++++++++++++++++++++++++++---
 2 files changed, 30 insertions(+), 6 deletions(-)

diff --git a/backend/src/backend/gen_context.cpp b/backend/src/backend/gen_context.cpp
index 893de34..d30369d 100644
--- a/backend/src/backend/gen_context.cpp
+++ b/backend/src/backend/gen_context.cpp
@@ -880,8 +880,8 @@ namespace gbe
           NOT_IMPLEMENTED;
         p->curr.execWidth = 1;
         p->curr.noMask = 1;
+        jip0 = p->n_instruction();
         p->JMPI(GenRegister::immud(0));
-        jip0 = p->n_instruction() - 1;
       p->pop();
 
       p->curr.predicate = GEN_PREDICATE_NONE;
@@ -905,8 +905,8 @@ namespace gbe
           NOT_IMPLEMENTED;
         p->curr.execWidth = 1;
         p->curr.noMask = 1;
+        jip1 = p->n_instruction();
         p->JMPI(GenRegister::immud(0));
-        jip1 = p->n_instruction() - 1;
       p->pop();
 
       p->curr.predicate = GEN_PREDICATE_NONE;
@@ -1457,7 +1457,7 @@ namespace gbe
       p->curr.noMask = 1;
       int jip = -(int)(p->n_instruction() - loop_start + 1) * 2;
       p->JMPI(zero);
-      p->patchJMPI(p->n_instruction()-1, jip);
+      p->patchJMPI(p->n_instruction()-2, jip);
       p->pop();
       // end of loop
     }
diff --git a/backend/src/backend/gen_encoder.cpp b/backend/src/backend/gen_encoder.cpp
index c372e36..1b79077 100644
--- a/backend/src/backend/gen_encoder.cpp
+++ b/backend/src/backend/gen_encoder.cpp
@@ -1050,13 +1050,37 @@ namespace gbe
 
   void GenEncoder::JMPI(GenRegister src) {
     alu2(this, GEN_OPCODE_JMPI, GenRegister::ip(), GenRegister::ip(), src);
+    NOP();
   }
 
   void GenEncoder::patchJMPI(uint32_t insnID, int32_t jumpDistance) {
     GenInstruction &insn = this->store[insnID];
-    assert(insnID < this->store.size());
-    assert(insn.header.opcode == GEN_OPCODE_JMPI);
-    this->setSrc1(&insn, GenRegister::immd(jumpDistance));
+    GBE_ASSERT(insnID < this->store.size());
+    GBE_ASSERT(insn.header.opcode == GEN_OPCODE_JMPI);
+    if ( (jumpDistance > -32767 && jumpDistance < 32768)
+         || (insn.header.predicate_control == GEN_PREDICATE_NONE)) {
+        this->setSrc1(&insn, GenRegister::immd(jumpDistance));
+    } else {
+      // For the conditional jump distance out of S15 range, we need to use an
+      // inverted jmp followed by a add ip, ip, distance to implement.
+      // A little hacky as we need to change the nop instruction to add
+      // instruction manually.
+      // FIXME there is an optimization method which we can insert a
+      // ADD instruction on demand. But that will need some extra analysis
+      // for all the branching instruction. And need to adjust the distance
+      // for those branch instruction's start point and end point contains
+      // this instruction.
+      insn.header.predicate_inverse ^= 1;
+      this->setSrc1(&insn, GenRegister::immd(2));
+      GenInstruction &insn2 = this->store[insnID+1];
+      GBE_ASSERT(insn2.header.opcode == GEN_OPCODE_NOP);
+      GBE_ASSERT(insnID < this->store.size());
+      insn2.header.predicate_control = GEN_PREDICATE_NONE;
+      insn2.header.opcode = GEN_OPCODE_ADD;
+      this->setDst(&insn2, GenRegister::ip());
+      this->setSrc0(&insn2, GenRegister::ip());
+      this->setSrc1(&insn2, GenRegister::immd(jumpDistance * 8));
+    }
   }
 
   void GenEncoder::CMP(uint32_t conditional, GenRegister src0, GenRegister src1) {
-- 
1.7.9.5