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[WebAssembly] Add some more ideas to README.txt.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@254880 91177308-0d34-0410-b5e6-96231b3b80d8
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Dan Gohman 2015-12-06 19:29:54 +00:00
parent 180d5cb8e1
commit 51b079cd28
1 changed files with 43 additions and 0 deletions
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lib/Target/WebAssembly/README.txt
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@ -47,3 +47,46 @@ expression stack across the jump (sometimes). We should (a) model this, and
(b) extend the stackifier to utilize it.
//===---------------------------------------------------------------------===//
The min/max operators aren't exactly a<b?a:b because of NaN and negative zero
behavior. The ARM target has the same kind of min/max instructions and has
implemented optimizations for them; we should do similar optimizations for
WebAssembly.
//===---------------------------------------------------------------------===//
AArch64 runs SeparateConstOffsetFromGEPPass, followed by EarlyCSE and LICM.
Would these be useful to run for WebAssembly too? Also, it has an option to
run SimplifyCFG after running the AtomicExpand pass. Would this be useful for
us too?
//===---------------------------------------------------------------------===//
When is it profitable to set isAsCheapAsAMove on instructions in WebAssembly?
//===---------------------------------------------------------------------===//
Register stackification uses the EXPR_STACK physical register to impose
ordering dependencies on instructions with stack operands. This is pessimistic;
we should consider alternate ways to model stack dependencies.
//===---------------------------------------------------------------------===//
Lots of things could be done in WebAssemblyTargetTransformInfo.cpp. Similarly,
there are numerous optimization-related hooks that can be overridden in
WebAssemblyTargetLowering.
//===---------------------------------------------------------------------===//
Instead of the OptimizeReturned pass, which should consider preserving the
"returned" attribute through to MachineInstrs and extending the StoreResults
pass to do this optimization on calls too. That would also let the
WebAssemblyPeephole pass clean up dead defs for such calls, as it does for
stores.
//===---------------------------------------------------------------------===//
Memset/memcpy/memmove should be marked with the "returned" attribute somehow,
even when they are translated through intrinsics.
//===---------------------------------------------------------------------===//