Optimize COFFObjectFile::sectionContainsSymbol a bit.

There is no need to compute the coff_section of the symbol just to compare the
pointer.

Inspired by the ELF implementation.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219233 91177308-0d34-0410-b5e6-96231b3b80d8
Don't check for null after calling COFFObjectFile::toSec.

It can only return null if passed a corrupted reference with a null Ref.p.
Checking for null is then an issue for asserts to check for internal
consistency, not control flow to check for invalid input.

I didn't add an assert(sec != nullptr) because toSec itself has a far more
complete assert.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219235 91177308-0d34-0410-b5e6-96231b3b80d8
R600/SI: Remove assertion in SIInstrInfo::areLoadsFromSameBasePtr()

Added a FIXME coment instead, we need to handle the case where the
two DS instructions being compared have different numbers of operands.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219236 91177308-0d34-0410-b5e6-96231b3b80d8
R600: Use MCAsmInfoELF as AMDGPUMCAsmInfo base class

The main reason for this is that the MCAsmInfo class,
which we were previously using as the base class, sets
PrivateGlobalPrefix to "L", which causes all global
functions that start with L to be treated as local symbols.

MCAsmInfoELF sets PrivateGlobalPrefix to ".L", which is what
we want, and it is probably a good idea to use this as the
base class anyway, since we are emitting ELF binaries.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219237 91177308-0d34-0410-b5e6-96231b3b80d8
R600: Remove some redundant initializations from AMDGPUMCAsmInfo

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219238 91177308-0d34-0410-b5e6-96231b3b80d8
LoopUnroll: Only check for ScalarEvolution analysis once, NFC

A follow-up commit will add use to a tight loop.  We might as well just
find it once anyway.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219239 91177308-0d34-0410-b5e6-96231b3b80d8
Add size_t MapVector::erase(KeyT) similar to the one in std::map.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219240 91177308-0d34-0410-b5e6-96231b3b80d8