| Daniel Dunbar | 8f4a8a6 | 2012-05-08 16:50:35 +0000 | [diff] [blame] | 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. |