An important tool for reasoning about programs without running them is dataflow analysis, which can be used to compute facts such as: an integer-valued variable is non-negative at a particular program point a conditional branch always goes one way an indirect write cannot modify a particular array Dataflow facts drive optimizations such as constant propagation…

(Here’s some optional background reading material.) We want fast integer overflow checking. Why? First, if the undefined behavior sanitizers go faster then testing goes faster. Second, when overhead drops below a certain point people will become willing to use UBSan to harden production code against integer overflows. This is already being done in parts of…