automatically exploiting cross-invocation parallelism using runtime ...

Workerthread 1Workerthread 2Workerthread 3Workerthread 41.11.2 1.3 1.41.51.62.32.42.12.23.13.23.43.53.3TimeFigure 4.4: Execution plan for TM-style speculation: each block A.B stands forthe B th iteration in the A th loop invocation: iteration 2.1 overlaps with iterations2.2, 2.3, 2.4, 2.7, 2.8, thus its memory accesses need to be compared with theirs even thoughall these iterations come from the same loop invocation and are guaranteed to be independent.erty of each loop invocation while still allowing threads to execute past the barrier withoutstalling. Since all existing speculative barrier synchronization techniques [30, 40, 45] requirespecialized hardware support, we refer to these techniques collectively as hardwarebasedbarrier speculation (HWBS).The work of Martínez et al. [40] is representative of the HWBS techniques. In thiswork, all worker threads start executing non-speculatively and are allowed to update theshared memory concurrently. A worker thread becomes speculative once it exceeds thebarrier boundary while other worker threads are still executing before the barrier. Whena worker thread becomes speculative, it first executes a checkpoint instruction to back up54