modern processor architectures make wcet analysis for hume challenging christian ferdinand absint...
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Modern Processor Architectures Make WCET Analysis for HUME
Challenging
Christian FerdinandAbsInt Angewandte Informatik GmbH
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The Timing ProblemPr
obab
ility
Execution Time
Best CaseExecution Time
Exact Worst CaseExecution Time
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End-to-end MeasurementsPr
obab
ility
Execution Time
Best CaseExecution Time
Exact Worst CaseExecution Time
MeasuredWorst-caseUnsafe:
Execution TimeMeasurement
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Hybrid ApproachsPr
obab
ility
Execution Time
Best CaseExecution Time
Exact Worst CaseExecution Time
Combination ofLocal Measurements
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Static Timing Analysis (Abstract Interpretation)
Prob
abili
ty
Execution Time
Best CaseExecution Time
Exact Worst CaseExecution Time
Safe Worst Case Execution TimeEstimate
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EmBounded Low-Level Timing Analysis for Renesas M32C85
High-level source code: Hume … … is translated to HAM code (Hume Abstract
Machine) HAM code is translated to C
Each HAM instruction becomes a snippet of C code
C code is translated to M32C binary code Each HAM instruction then becomes a snippet of M32C code
Use AbsInt’s aiT to analyze the M32C code corresponding to the HAM instructions
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aiT vs. Measurement
Good precision in general
Note for MatchRule: Measurement error up to 3 cycles
See IFL06 paperArmelle Bonenfant et al.,
Worst-Case Execution Times for a Purely Functional Language
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aiT WCET Analyzer Structure
Interprocedural PAG-generated analyzers based
on AI
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Contexts with Loops
INTERPROC: VIVUINTERPROC_L: 3
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e300
e300 / PPC603e +- 450 MHz Double precision FPU Caches (LRU) + store
buffer Superscalar pipeline with
out-of-order execution Branch prediction (static) Available in various
processors, e.g. Freescale MPC82xx
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Recursive C-Program Example
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Conclusion
On M32-class processors Current WCET analysis for Hume works well
On e300-class processors Current WCET analysis for Hume will largely overestimate