International Business Machines Corporation

Wai Hung Tsang

Ettore Tiotto

Bardia Mahjour

Shimin Cui

Hubert Shun Kwan Tong

Jinsong Ji

Jun Shirako

Zarko Todorovski

Avery Laird

Bangtian Liu

Prithayan Barua

Maryam Dehnavi

Wei Huang

A vectorization factor to be used in vectorization of an epilogue loop in program code is automatically selected. The automatically selecting includes selecting the vectorization factor from a plurality of candidate vectorization factors based on one or more considerations relating to vectorizing the epilogue loop. The vectorization factor that is automatically selected is used in vectorizing the epilogue loop.

Selecting an epilogue vectorization factor for use in computer processing

Vectorization of program code by way of a method that includes obtaining program code to be compiled. The program code has a loop that includes a control-flow having divergent branch conditions. The method includes compiling the program code to produce compiled code. The compiling includes performing compile-time analysis of the loop based on an assumption of dynamic uniformity, and determining from the analysis a vectorizable access pattern of the loop. The compiling also includes vectorizing the loop as part of the compiling the program code, including compiling the loop. The vectorizing includes providing run-time checks in the compiled code. The run-time checks are configured for checking for dynamically uniform conditions for vector processing at run-time to control program execution flow based on a result of the checking. The method also includes outputting the compiled code for execution.

Control flow auto-vectorization using run-time checks and compile-time analysis

Code pattern matching is performed within computer code to determine whether the computer code includes an idiom from a predefined set of idioms. Based on determining that the computer code includes the idiom, a set of data items of the idiom to be analyzed is determined. The set of data items is analyzed with respect to one or more corresponding values from the computer code based on a set of constraints defined for the idiom to determine whether the set of data items satisfy one or more predefined conditions for the idiom. Based on the analyzing indicating that the one or more predefined conditions are satisfied, one or more code segments of the computer code including the idiom are replaced with replacement code to provide revised computer code.

Transformation of computer code based on idiom recognition and value constraint analysis

Predictive dead store elimination is provided. The method comprises identifying, in a program, a first store operation and a second store operation in a program loop that comprise a store pair with a same loop-invariant base address and determining whether the store pair is a predictive dead store elimination candidate. Responsive to a determination that the store pair is a predictive dead store elimination candidate, the method eliminates the first store operation in each iteration of the program loop, except the last DSRC (dead store recurrence constant) iterations and sinks the first store operation in the last DSRC iterations to after the program loop.

Predictive dead store elimination

A loop within computer code is transformed to minimize loop iterations. A determination is made using statistical information relating to the loop whether the loop that has an early exit indication is to be transformed to minimize iterations of the loop. Based on determining that the loop is to be transformed, the loop is transformed.

Transformation of a loop within computer code to minimize iterations

Early exit of a loop is performed. A determination is made as to whether a loop within computer code reaches a fixed point of processing, which is predefined. Based on determining that the loop reaches the fixed point of processing, at least one indication is included in the loop to perform an early exit of the loop prior to a last iteration of the loop.

Fixed point early exit of a loop within computer code

Feedback-directed pass pipeline optimization in static compilation includes receiving a set of source input of source code by a static compiler. The static compiler initiates a compilation operation on the source code in which, in a pass pipeline during the compilation operation that creates an intermediate representation (IR) representing the source code, a set of optimization diagnostics identified during a first pass of the pass pipeline is emitted into a side file. The pass pipeline is then optimized using the set of optimization diagnostics.

Feedback-directed pass pipeline optimization in static compilation

Aspects include modeling data cache utilization for each loop in a loop nest; estimating total data cache lines fetched in one iteration of the loop; and determining the possibility of data cache reuse across loop iterations using data cache lines fetched and associativity constraints. Aspects also include estimating, for memory reference pairs, reuse by one reference of data cache line fetched by another; estimating total number of cache misses for all iterations of the loop; and estimating total number of cache misses of a reference for iterations of a next outer loop as equal to total cache misses for an entire inner loop. Aspects further include estimating memory cost of a loop unroll and jam transformation, without performing the transformation; and extending a data cache model to estimate best unroll-and-jam factors for the loop nest, capable of minimizing total cache misses incurred by the memory references in the loop body.

Analysis for modeling data cache utilization

Aspects include executing a first phase that includes injecting instrumentation into program code in response to identifying an inner conditional check in the program code and running the instrumented program with a representative workload. The injecting includes duplicating the inner conditional check and placing a duplicate of the inner conditional check before a respective original nested conditional check in the program code to create an instrumented program. The instrumented program includes a plurality of basic blocks including original basic blocks and a newly added basic block that includes the duplicate of the inner conditional check. The method also includes executing a second phase that includes collecting execution frequency values from counters associated with the basic blocks to form metadata used to make optimization decisions for the program code.

Growing community of inventors

Markham, Canada

Wai Hung Tsang