which are effectively smart pointers to Value*'s.  They are both very light
weight and simple, and react to values being destroyed or being RAUW'd.

WeakVN does a best effort to follow a value around, including through RAUW 
operations and will get nulled out of the value is destroyed.  This is useful
for the eventual "metadata that references a value" work, because it is a
reference to a value that does not show up on its use_* list.

AssertingVH is a pointer that compiles down to a dumb raw pointer when 
assertions are disabled.  When enabled, it emits an assertion if the 
pointed-to value is destroyed while it is still being referenced.  This
is very useful for Maps and other things, and should have caught the recent
bugs in CallGraph and Reassociate, for example.

llvm-svn: 68149

Throttle back "fold select into operand" transformation. InstCombine should not generate selects of two constants unless they are selects of 0 and 1.

e.g.
define i32 @t1(i32 %c, i32 %x) nounwind {
       %t1 = icmp eq i32 %c, 0
       %t2 = lshr i32 %x, 18
       %t3 = select i1 %t1, i32 %t2, i32 %x
       ret i32 %t3
}

was turned into

define i32 @t2(i32 %c, i32 %x) nounwind {
       %t1 = icmp eq i32 %c, 0
       %t2 = select i1 %t1, i32 18, i32 0
       %t3 = lshr i32 %x, %t2
       ret i32 %t3
}

For most targets, that means materializing two constants and then a select. e.g. On x86-64

movl    %esi, %eax
shrl    $18, %eax
testl   %edi, %edi
cmovne  %esi, %eax
ret

=>

xorl    %eax, %eax
testl   %edi, %edi
movl    $18, %ecx
cmovne  %eax, %ecx
movl    %esi, %eax
shrl    %cl, %eax
ret

Also, the optimizer and codegen can reason about shl / and / add, etc. by a constant. This optimization will hinder optimizations using ComputeMaskedBits.

llvm-svn: 68142

llvm-svn: 68134

llvm-svn: 68133

entered via fall-through. Don't miss fallthroughs from blocks
terminated by conditional branches. Also, move
isOnlyReachableByFallthrough out of line.

llvm-svn: 68129

Patch by Jay Foad.

llvm-svn: 68120

llvm::sys::getOS{Name,Version}.

Right now the implementation just derives from LLVM_HOSTTRIPLE (which
is wrong, but it doesn't look like we have a define for the target
triple). Ideally this routine would actually be able to compute the
triple for targets we care about.

llvm-svn: 68118

llvm-svn: 68113

llvm-svn: 68109

llvm-svn: 68100

llvm-svn: 68099

Remove the "fast" cases for spill and restore point determination, as these were subtlely wrong in obscure cases.  Patch the testcase
to account for this change.

llvm-svn: 68093

llvm-svn: 68092

instructions. This fixes lua.

llvm-svn: 68083

X86 address mode isel tweak. If the base of the address is also used by a CopyToReg (i.e. it's likely live-out), do not fold the sub-expressions into the addressing mode to avoid computing the address twice. The CopyToReg use will be isel'ed to a LEA, re-use it for address instead.

This is not yet enabled.

llvm-svn: 68082

only reachable via fall-through edges. This dramatically reduces the
number of labels printed, and thus also the number of labels the
assembler must parse and remember.

llvm-svn: 68073

Loop Index Split can eliminate a loop if it can determin if loop body is executed only once. There was a bug in determining IV based value of the iteration for which the loop body is executed. Fix it.

llvm-svn: 68071

When optimzing a mul by immediate into two, the resulting mul's should get a x86 specific node to avoid dag combiner from hacking on them further.

llvm-svn: 68066

Turn a 2-address instruction into a 3-address one when it's profitable even if the two-address operand is killed.
e.g.
%reg1024<def> = MOV r1
%reg1025<def> = ADD %reg1024, %reg1026
r0            = MOV %reg1025

If it's not possible / profitable to commute ADD, then turning ADD into a LEA saves a copy.

llvm-svn: 68065

llvm-svn: 68059

llvm-svn: 68057

llvm-svn: 68054

llvm-svn: 68050

Walking an invalidated iterator is not a good idea.

llvm-svn: 68047

llvm-svn: 68036

llvm-svn: 68034

llvm-svn: 68033

Do not propagate ELF-specific stuff (data.rel) into other targets. This simplifies code and also ensures correctness.

llvm-svn: 68032

llvm-svn: 68031

llvm-svn: 68007

llvm-svn: 68006

llvm-svn: 68005

Extend the relocation tracker handler, so we can filter on different 'kinds' of relocations required.

llvm-svn: 68004

when using -soft-float.
Based on a patch by Jakob Stoklund Olesen.

llvm-svn: 67996

hackish workarounds from memdep

llvm-svn: 67971

llvm-svn: 67953

llvm-svn: 67950

llvm-svn: 67949

of operands in an address in so many places.

llvm-svn: 67945

a CALL and a RET node more generic. Add a test for tail calls with a void
return.

llvm-svn: 67943