This is an attempt to reland D42600 and enabling this optimisation by default.

This also resolves the issue pointed out in the context of PGO build.

Differential Revision: https://reviews.llvm.org/D42600

This reverts commit 1ddfd1c8186735c62b642df05c505dc4907ffac4.

The original commit causes a Chrome build assertion failure with
ThinLTO: https://crbug.com/1443635

Try to reland D42600

Differential Revision: https://reviews.llvm.org/D42600

Fix the ARM backend's analyzeBranch so it doesn't ignore predicated
return instructions, and make the MachineVerifier rule more strict.

Differential Revision: https://reviews.llvm.org/D40061

This reverts r369664 (git commit 51f48295cbe8fa3a44db263b528dd9f7bae7bf9a)

It causes many benchmark regressions, internally and in llvm's benchmark suite.

llvm-svn: 370398

Patch https://reviews.llvm.org/D43256 introduced more aggressive loop layout optimization which depends on profile information. If profile information is not available, the statically estimated profile information(generated by BranchProbabilityInfo.cpp) is used. If user program doesn't behave as BranchProbabilityInfo.cpp expected, the layout may be worse.

To be conservative this patch restores the original layout algorithm in plain mode. But user can still try the aggressive layout optimization with -force-precise-rotation-cost=true.

Differential Revision: https://reviews.llvm.org/D65673

llvm-svn: 369664

It caused assertions to fire when building Chromium:

  lib/CodeGen/LiveDebugValues.cpp:331: bool
  {anonymous}::LiveDebugValues::OpenRangesSet::empty() const: Assertion
  `Vars.empty() == VarLocs.empty() && "open ranges are inconsistent"' failed.

See https://crbug.com/992871#c3 for how to reproduce.

> Patch https://reviews.llvm.org/D43256 introduced more aggressive loop layout optimization which depends on profile information. If profile information is not available, the statically estimated profile information(generated by BranchProbabilityInfo.cpp) is used. If user program doesn't behave as BranchProbabilityInfo.cpp expected, the layout may be worse.
>
> To be conservative this patch restores the original layout algorithm in plain mode. But user can still try the aggressive layout optimization with -force-precise-rotation-cost=true.
>
> Differential Revision: https://reviews.llvm.org/D65673

llvm-svn: 368579

Patch https://reviews.llvm.org/D43256 introduced more aggressive loop layout optimization which depends on profile information. If profile information is not available, the statically estimated profile information(generated by BranchProbabilityInfo.cpp) is used. If user program doesn't behave as BranchProbabilityInfo.cpp expected, the layout may be worse.

To be conservative this patch restores the original layout algorithm in plain mode. But user can still try the aggressive layout optimization with -force-precise-rotation-cost=true.

Differential Revision: https://reviews.llvm.org/D65673

llvm-svn: 368339

The arm condition codes for GE is N==V (and for LT is N!=V). If the source of
flags cannot set V (overflow), such as a cmp against #0, then we can use the
simpler PL and MI conditions that only check N. As these PL/MI conditions are
simpler than GE/LT, other passes like the peephole optimiser can have a better
time optimising away the redundant CMPs.

The exception is the VSEL instruction, which cannot take the PL code, so there
the transform favours GE.

Differential Revision: https://reviews.llvm.org/D64160

llvm-svn: 365117