LLVM compiler recognizes opportunities to transform a branch into IR select instruction(s) - later it will be lowered into X86::CMOV instruction, assuming no other optimization eliminated the SelectInst.
However, it is not always profitable to emit X86::CMOV instruction. For example, branch is preferable over an X86::CMOV instruction when:
1. Branch is well predicted
2. Condition operand is expensive, compared to True-value and the False-value operands
In CodeGenPrepare pass there is a shallow optimization that tries to convert SelectInst into branch, but it is not enough.
This commit, implements machine optimization pass that converts X86::CMOV instruction(s) into branch, based on a conservative heuristic.
Differential Revision: https://reviews.llvm.org/D34769
llvm-svn: 308142
Some platforms have problems with emmiting constructors when class
templates get explicitly instantiated.
This patch fixes the bug reported in D35315 by replacing `= default`
with an empty constructor body.
llvm-svn: 308140
Finally figured out that some bots were failing from r308114
with the message:
llvm-lto2: LTO::run failed: No available targets are compatible with this triple.
after adding in some other checking that finally caused this to show up
in the FileCheck output.
Added "REQUIRES: x86-registered-target" which should fix it.
llvm-svn: 308119
This restores r308078/r308079 with a fix for bot non-determinisim (make
sure we run llvm-lto in single threaded mode so the debug output doesn't get
interleaved).
llvm-svn: 308114
Summary:
Currently these methods call ConstantDataVector::getSplatValue which uses getElementsAsConstant to create a Constant object representing the element value. This method incurs a map lookup to see if we already have created such a Constant before and if not allocates a new Constant object.
This patch changes these methods to use getElementAsAPFloat and getElementAsInteger so we can just examine the data values directly.
Reviewers: spatel, pcc, dexonsmith, bogner, craig.topper
Reviewed By: craig.topper
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D35040
llvm-svn: 308112
Summary:
If one side simplifies to the identity value for inner opcode, we can replace the value with just the operation that can't be simplified.
I've removed a couple now unneeded special cases in visitAnd and visitOr. There are probably other cases I missed.
Reviewers: spatel, majnemer, hfinkel, dberlin
Reviewed By: spatel
Subscribers: grandinj, llvm-commits, spatel
Differential Revision: https://reviews.llvm.org/D35451
llvm-svn: 308111
This fold hit the trifecta:
1. It was untested.
2. It oversteps (multiuse is not checked, so increases instruction count).
3. It is incomplete (doesn't work for vectors).
llvm-svn: 308102
that appears to exhibit non-determinism and is flaking on the bots
pretty consistently.
r308078: [ThinLTO] Ensure we always select the same function copy to import
r308079: Require asserts in new test that uses debug flag
llvm-svn: 308095
objects to start at the same address
As discussed on the ML, there's consensus that this is what the implementations
do and it seems sensible.
llvm-svn: 308090
function to every defined function known to LLVM as a library function.
LLVM can introduce calls to these functions either by replacing other
library calls or by recognizing patterns (such as memset_pattern or
vector math patterns) and replacing those with calls. When these library
functions are actually defined in the module, we need to have reference
edges to them initially so that we visit them during the CGSCC walk in
the right order and can effectively rebuild the call graph afterward.
This was discovered when building code with Fortify enabled as that is
a common case of both inline definitions of library calls and
simplifications of code into calling them.
This can in extreme cases of LTO-ing with libc introduce *many* more
reference edges. I discussed a bunch of different options with folks but
all of them are unsatisfying. They either make the graph operations
substantially more complex even when there are *no* defined libfuncs, or
they introduce some other complexity into the callgraph. So this patch
goes with the simplest possible solution of actual synthetic reference
edges. If this proves to be a memory problem, I'm happy to implement one
of the clever techniques to save memory here.
llvm-svn: 308088
If the `long-calls` feature flags is enabled, disable use of the `jal`
instruction. Instead of that call a function by by first loading its
address into a register, and then using the contents of that register.
Differential revision: https://reviews.llvm.org/D35168
llvm-svn: 308087
The type needs to be casted back to the original argument type.
Fixes an assert that for some reason is only run when
using -debug.
Includes an additional combine to avoid test regressions
from having conversions mixed with multiple Assert[SZ]ext
nodes. On subtargets where i16 is legal, this was producing an i32
register with an i16 AssertZExt, truncated to i16 with another i8
AssertZExt.
t2: i32,ch = CopyFromReg t0, Register:i32 %vreg0
t3: i16 = truncate t2
t5: i16 = AssertZext t3, ValueType:ch:i8
t6: i8 = truncate t5
t7: i32 = zero_extend t6
llvm-svn: 308082
