Files
llvm/lib/Analysis
Alon Zakai 683212b71c [WebAssembly] Add Emscripten OS definition + small_printf
The Emscripten OS provides a definition of __EMSCRIPTEN__, and also that it
supports iprintf optimizations.

Also define small_printf optimizations, which is a printf with float support
but not long double (which in wasm can be useful since long doubles are 128
bit and force linking of float128 emulation code). This part is based on
sunfish's https://reviews.llvm.org/D57620 (which can't land yet since
the WASI integration isn't ready yet).

Differential Revision: https://reviews.llvm.org/D60167

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@357552 91177308-0d34-0410-b5e6-96231b3b80d8
2019-04-03 01:08:35 +00:00
..
2019-03-08 21:03:06 +00:00
2019-03-29 22:27:10 +00:00

Analysis Opportunities:

//===---------------------------------------------------------------------===//

In test/Transforms/LoopStrengthReduce/quadradic-exit-value.ll, the
ScalarEvolution expression for %r is this:

  {1,+,3,+,2}<loop>

Outside the loop, this could be evaluated simply as (%n * %n), however
ScalarEvolution currently evaluates it as

  (-2 + (2 * (trunc i65 (((zext i64 (-2 + %n) to i65) * (zext i64 (-1 + %n) to i65)) /u 2) to i64)) + (3 * %n))

In addition to being much more complicated, it involves i65 arithmetic,
which is very inefficient when expanded into code.

//===---------------------------------------------------------------------===//

In formatValue in test/CodeGen/X86/lsr-delayed-fold.ll,

ScalarEvolution is forming this expression:

((trunc i64 (-1 * %arg5) to i32) + (trunc i64 %arg5 to i32) + (-1 * (trunc i64 undef to i32)))

This could be folded to

(-1 * (trunc i64 undef to i32))

//===---------------------------------------------------------------------===//