A method, implemented at a computer system that includes at least one processor, for diffing a subject replayable execution trace against a plurality of comparison replayable execution traces, the method comprising: accessing a subject replayable execution trace (300, 401a, 402a, 403a), and accessing a plurality of comparison replayable execution traces (300, 401b, 402b, 403b), each replayable execution trace representing a corresponding sequence of executable instructions that executed as part of a corresponding executing entity; identifying a set of mappings among the plurality of comparison replayable execution traces, each mapping of the set of mappings identifying two or more corresponding comparison sections of consecutive executable instructions within the plurality of comparison replayable execution traces that execute equivalently, each comparison section in each mapping being from a different one of the plurality of comparison replayable execution traces, wherein two or more corresponding comparison sections of consecutive executable instructions within the plurality of comparison replayable execution traces execute equivalently if both comparison sections of consecutive executable instructions produce the same outputs given the same inputs; based on the set of mappings, identifying a plurality of distinct comparison sections within the plurality of comparison replayable execution traces, each distinct comparison section either (i) lacking a mapping in the set of mappings, or (ii) being a representative comparison section from a different mapping in the set of mappings; comparing the subject replayable execution trace and the plurality of comparison replayable execution traces, including at least comparing each of a plurality of subject sections of consecutive executable instructions within the subject execution trace against one or more of the plurality of distinct comparison sections; based on the comparing, determining a comparison status of each of the plurality of subject sections, including determining at least one of whether each subject section is (i) equal to at least one corresponding distinct comparison section, or (ii) different than the plurality of distinct comparison sections, wherein the determined comparison status of at least one particular subject section with respect at least one particular corresponding distinct comparison section is applied to each additional comparison section to which the at least one particular distinct comparison section is mapped in the set of mappings; and providing an indicia of a result of the determining to a software component at the computer system, or to another computer system. accessing a subject replayable execution trace (300, 401a, 402a, 403a), and accessing a plurality of comparison replayable execution traces (300, 401b, 402b, 403b), each replayable execution trace representing a corresponding sequence of executable instructions that executed as part of a corresponding executing entity; identifying a set of mappings among the plurality of comparison replayable execution traces, each mapping of the set of mappings identifying two or more corresponding comparison sections of consecutive executable instructions within the plurality of comparison replayable execution traces that execute equivalently, each comparison section in each mapping being from a different one of the plurality of comparison replayable execution traces, wherein two or more corresponding comparison sections of consecutive executable instructions within the plurality of comparison replayable execution traces execute equivalently if both comparison sections of consecutive executable instructions produce the same outputs given the same inputs; based on the set of mappings, identifying a plurality of distinct comparison sections within the plurality of comparison replayable execution traces, each distinct comparison section either (i) lacking a mapping in the set of mappings, or (ii) being a representative comparison section from a different mapping in the set of mappings; comparing the subject replayable execution trace and the plurality of comparison replayable execution traces, including at least comparing each of a plurality of subject sections of consecutive executable instructions within the subject execution trace against one or more of the plurality of distinct comparison sections; based on the comparing, determining a comparison status of each of the plurality of subject sections, including determining at least one of whether each subject section is (i) equal to at least one corresponding distinct comparison section, or (ii) different than the plurality of distinct comparison sections, wherein the determined comparison status of at least one particular subject section with respect at least one particular corresponding distinct comparison section is applied to each additional comparison section to which the at least one particular distinct comparison section is mapped in the set of mappings; and providing an indicia of a result of the determining to a software component at the computer system, or to another computer system.