blob: 78b3123cde85b04744a79b8277d9de6da5b8115f [file] [log] [blame]
Dan Gohman10e730a2015-06-29 23:51:55 +00001//===-- README.txt - Notes for WebAssembly code gen -----------------------===//
2
3This WebAssembly backend is presently in a very early stage of development.
4The code should build and not break anything else, but don't expect a lot more
5at this point.
6
7For more information on WebAssembly itself, see the design documents:
8 * https://github.com/WebAssembly/design/blob/master/README.md
9
10The following documents contain some information on the planned semantics and
11binary encoding of WebAssembly itself:
12 * https://github.com/WebAssembly/design/blob/master/AstSemantics.md
13 * https://github.com/WebAssembly/design/blob/master/BinaryEncoding.md
14
JF Bastienf05f6fd2015-12-05 19:36:33 +000015The backend is built, tested and archived on the following waterfall:
16 https://build.chromium.org/p/client.wasm.llvm/console
17
18The backend's bringup is done using the GCC torture test suite first since it
19doesn't require C library support. Current known failures are in
20known_gcc_test_failures.txt, all other tests should pass. The waterfall will
21turn red if not. Once most of these pass, further testing will use LLVM's own
22test suite.
23
JF Bastien86bc9152015-07-06 21:41:59 +000024Interesting work that remains to be done:
25* Write a pass to restructurize irreducible control flow. This needs to be done
26 before register allocation to be efficient, because it may duplicate basic
27 blocks and WebAssembly performs register allocation at a whole-function
28 level. Note that LLVM's GPU code has such a pass, but it linearizes control
29 flow (e.g. both sides of branches execute and are masked) which is undesirable
30 for WebAssembly.
JF Bastien86bc9152015-07-06 21:41:59 +000031
Dan Gohman10e730a2015-06-29 23:51:55 +000032//===---------------------------------------------------------------------===//
Dan Gohmandfa81d82015-11-20 03:08:27 +000033
Dan Gohman81719f82015-11-25 16:55:01 +000034set_local instructions have a return value. We should (a) model this,
Dan Gohmandfa81d82015-11-20 03:08:27 +000035and (b) write optimizations which take advantage of it. Keep in mind that
36many set_local instructions are implicit!
37
38//===---------------------------------------------------------------------===//
39
40Load and store instructions can have a constant offset. We should (a) model
41this, and (b) do address-mode folding with it.
42
43//===---------------------------------------------------------------------===//
44
45Br, br_if, and tableswitch instructions can support having a value on the
46expression stack across the jump (sometimes). We should (a) model this, and
47(b) extend the stackifier to utilize it.
48
49//===---------------------------------------------------------------------===//