GBE: we should allocate register for ExtractElement insn.

We should allocate register when we firstly visit ExtractElement
instruction, as we may refer the value before we visit that instruction
at the emit instruction pass.

The case which trigger this corner case is as below:
Clang/llvm may generate some code similar to the following IRs:

... (there is no definition of %7)
  br label 2

label1:
  %10 = add  i32 %7, %6
  ...
  ret

label2:
  %8 = load <4 x i8> addrspace(1)* %3, align 4, !tbaa !1
  %7 = extractelement <4 x i8> %8, i32 0
  ...
  br label1

The value %7 is assigned after label2 but is referred at label1.
From the control flow, the IRs is valid. As the reference will
be executed after the assignment. But the previous implementation
doesn't allocate proxyvalue for %7, that's the root cause why
it triggers an assert when visit the instruction %10 = add i32 %7, %6

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

diff --git a/backend/src/llvm/llvm_gen_backend.cpp b/backend/src/llvm/llvm_gen_backend.cpp
index 0d4fb87..18e6967 100644 (file)
--- a/backend/src/llvm/llvm_gen_backend.cpp
+++ b/backend/src/llvm/llvm_gen_backend.cpp
@@ -1846,8 +1846,7 @@ namespace gbe
     }
   }
 
-  void GenWriter::regAllocateExtractElement(ExtractElementInst &I) {}
-  void GenWriter::emitExtractElement(ExtractElementInst &I) {
+  void GenWriter::regAllocateExtractElement(ExtractElementInst &I) {
     Value *vec = I.getVectorOperand();
     const Value *index = I.getIndexOperand();
     const ConstantInt *c = dyn_cast<ConstantInt>(index);
@@ -1856,6 +1855,9 @@ namespace gbe
     regTranslator.newValueProxy(vec, &I, i, 0);
   }
 
+  void GenWriter::emitExtractElement(ExtractElementInst &I) {
+  }
+
   void GenWriter::regAllocateShuffleVectorInst(ShuffleVectorInst &I) {}
   void GenWriter::emitShuffleVectorInst(ShuffleVectorInst &I) {}