1 llvm-diff - LLVM structural 'diff' 2 ================================== 3 4 5 SYNOPSIS 6 -------- 7 8 9 **llvm-diff** [*options*] *module 1* *module 2* [*global name ...*] 10 11 12 DESCRIPTION 13 ----------- 14 15 16 **llvm-diff** compares the structure of two LLVM modules, primarily 17 focusing on differences in function definitions. Insignificant 18 differences, such as changes in the ordering of globals or in the 19 names of local values, are ignored. 20 21 An input module will be interpreted as an assembly file if its name 22 ends in '.ll'; otherwise it will be read in as a bitcode file. 23 24 If a list of global names is given, just the values with those names 25 are compared; otherwise, all global values are compared, and 26 diagnostics are produced for globals which only appear in one module 27 or the other. 28 29 **llvm-diff** compares two functions by comparing their basic blocks, 30 beginning with the entry blocks. If the terminators seem to match, 31 then the corresponding successors are compared; otherwise they are 32 ignored. This algorithm is very sensitive to changes in control flow, 33 which tend to stop any downstream changes from being detected. 34 35 **llvm-diff** is intended as a debugging tool for writers of LLVM 36 passes and frontends. It does not have a stable output format. 37 38 39 EXIT STATUS 40 ----------- 41 42 43 If **llvm-diff** finds no differences between the modules, it will exit 44 with 0 and produce no output. Otherwise it will exit with a non-zero 45 value. 46 47 48 BUGS 49 ---- 50 51 52 Many important differences, like changes in linkage or function 53 attributes, are not diagnosed. 54 55 Changes in memory behavior (for example, coalescing loads) can cause 56 massive detected differences in blocks. 57
