Bidirectional liveness analysis, or how less than half of the Alpha’s registers are used

Abstract

Interprocedural data flow analyses of executable programs suffer from the conservative assumptions that need to be made because no precise control flow graph is available and because registers are spilled onto the stack. This paper discusses the exploitation of calling-conventions in executable code data flow analyses to avoid the propagation of the conservative assumptions throughout a program.Based on this exploitation, the existing backward liveness analyses are improved, and a complementary forward liveness analysis is proposed. For the SPECint2000 programs compiled for the Alpha architecture, the combined forward and improved backward analysis on average finds 62% more free registers than the existing stateof-the-art liveness analysis.With the improved analysis, we are able to show that on average less than half of the registers of the RISC Alpha architecture are used. This contradicts the common wisdom that compilers can exploit large, uniform register files as found on RISC architectures.

Link-time compaction and optimization of ARM executables

“…Other work on link-time optimization has targeted program size on the Alpha platform [Debray et al 2000;De Sutter et al 2002, 2005b. In that work, an average code size reduction of 27% was achieved on benchmarks similar to those used in this paper.…”

“…Optimizing linkers have a wholeprogram overview over the compiled object files and precompiled code libraries and optimize them together to produce smaller, faster, or less power-hungry executable binaries. Existing research prototypes such as Squeeze++ [De Sutter et al 2002, 2005bDebray et al 2000 and alto [Muth et al 2001], and commercial tools such as OM [Srivastava and Wall 1994] and Spike [Cohn et al 1997] have shown that significant code size reductions and speedups can indeed be obtained with link-time optimization. Unfortunately for the embedded systems community, these tools all operate in the Tru64Unix workstation and server environment.…”

Obfuscated integration of software protections

“…To test whether sufficient glue code can be generated to make a fragment set actually factorable, we use a bidirectional, context-sensitive interprocedural liveness analysis [32]. To identify already available constants as input to dispatchers, we perform a flow-sensitive, context-sensitive (k-depth with k=1) constant propagation analysis [33].…”

Link-time smart card code hardening

“…In such cases, we need to find one or more free (i.e., dead) registers to rename registers before performing the duplication, or to store copies of the original source operand values temporarily. Our prototype finds such free registers by means of a state-of-the-art bidirectional context-sensitive interprocedural liveness analysis [18]. When free registers are found, we can simply use them, as shown in Figure 2(b).…”