Yutaka Ota

A new compilation technique for SIMD code generation across basic block boundaries

Although SIMD instructions are effective for many digital signal processing applications, current compilers cannot take full advantage of SIMD instructions. One factor inhibiting SIMD code generation is control flow structure; the target scope of SIMD code generation is currently limited to single basic block or loop that consists of single basic block. SIMD instructions cannot be mapped typically across basic block boundaries even if basic blocks inside the control structure have enough parallelism. In this paper, a new compilation technique to generate SIMD code without modifying control flow structure is proposed. The data dependency between basic blocks is exploited to generate SIMD instructions. The packing cost is introduced for effective vectorization to maintain data dependency across basic block boundaries. Experimental results show that the new SIMD code generation technique reduced 67% of dynamic execution cycles of inter prediction in H.264 decoder.

Generation of Pack Instruction Sequence for Media Processors Using Multi-Valued Decision Diagram

SIMD instructions are often implemented in modern multimedia oriented processors. Although SIMD instructions are useful for many digital signal processing applications, most compilers do not exploit SIMD instructions. The difficulty in the utilization of SIMD instructions stems from data parallelism in registers. In assembly code generation, the positions of data in registers must be noted. A technique of generating pack instructions which pack or reorder data in registers is essential for exploitation of SIMD instructions. This paper presents a code generation technique for SIMD instructions with pack instructions. SIMD instructions are generated by finding and grouping the same operations in programs. After the SIMD instruction generation, pack instructions are generated. In the pack instruction generation, Multi-valued Decision Diagram (MDD) is introduced to represent and to manipulate sets of packed data. Experimental results show that the proposed code generation technique can generate assembly code with SIMD and pack instructions performing repacking of 8 packed data in registers for a RISC processor with a dual-issue coprocessor which supports SIMD and pack instructions. The proposed method achieved speedup ratio up to about 8.5 by SIMD instructions and multiple-issue mechanism of the target processor.

Pack instruction generation for media pUsing multi-valued decision diagram

SIMD instructions are often implemented in modern multimedia oriented processors. Although SIMD instructions are useful for many digital signal processing applications, most compilers do not exploit SIMD instructions. The difficulty in the utilization of SIMD instructions stems from data parallelism in registers. In assembly code generation, the positions of data in registers must be noted. A technique of generating pack instructions which pack or reorder data in registers is essential for exploitation of SIMD instructions. This paper presents a code generation technique for SIMD instructions with pack instructions. SIMD instructions are generated by finding and grouping the same operations in programs. After the SIMD instruction generation, pack instructions are generated. In the pack instruction generation, multi-valued decision diagram (MDD) is introduced to represent and to manipulate sets of packed data. Experimental results show that our code generation technique can generate assembly code with SIMD and pack instructions performing complex repacking of 8 packed data in registers for a commercial VLIW processor with 6 pack instructions and achieved speedup ratio of up to 7.7.