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When a block has no terminator instructions, getFirstTerminator() returns end(), which can't be used in dominance checks. Check dominance for phi operands separately. Also, remove some bits from WebAssemblyRegStackify.cpp that were causing trouble on the same testcase; they were left behind from an earlier experiment. Differential Revision: http://reviews.llvm.org/D15210 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@254662 91177308-0d34-0410-b5e6-96231b3b80d8
//===-- README.txt - Notes for WebAssembly code gen -----------------------===// This WebAssembly backend is presently in a very early stage of development. The code should build and not break anything else, but don't expect a lot more at this point. For more information on WebAssembly itself, see the design documents: * https://github.com/WebAssembly/design/blob/master/README.md The following documents contain some information on the planned semantics and binary encoding of WebAssembly itself: * https://github.com/WebAssembly/design/blob/master/AstSemantics.md * https://github.com/WebAssembly/design/blob/master/BinaryEncoding.md Interesting work that remains to be done: * Write a pass to restructurize irreducible control flow. This needs to be done before register allocation to be efficient, because it may duplicate basic blocks and WebAssembly performs register allocation at a whole-function level. Note that LLVM's GPU code has such a pass, but it linearizes control flow (e.g. both sides of branches execute and are masked) which is undesirable for WebAssembly. //===---------------------------------------------------------------------===// set_local instructions have a return value. We should (a) model this, and (b) write optimizations which take advantage of it. Keep in mind that many set_local instructions are implicit! //===---------------------------------------------------------------------===// Load and store instructions can have a constant offset. We should (a) model this, and (b) do address-mode folding with it. //===---------------------------------------------------------------------===// Br, br_if, and tableswitch instructions can support having a value on the expression stack across the jump (sometimes). We should (a) model this, and (b) extend the stackifier to utilize it. //===---------------------------------------------------------------------===//