While there, I noticed that the transform "undef >>a X -> undef" was wrong.
For example if X is 2 then the top two bits must be equal, so the result can
not be anything.  I fixed this in the constant folder as well.  Also, I made
the transform for "X << undef" stronger: it now folds to undef always, even
though X might be zero.  This is in accordance with the LangRef, but I must
admit that it is fairly aggressive.  Also, I added "i32 X << 32 -> undef"
following the LangRef and the constant folder, likewise fairly aggressive.

llvm-svn: 123417

llvm-svn: 123396

llvm-svn: 123383

This is a minor extension of SROA to handle a special case that is
important for some ARM NEON operations.  Some of the NEON intrinsics
return multiple values, which are handled as struct types containing
multiple elements of the same vector type.  The corresponding return
types declared in the arm_neon.h header have equivalent arrays.  We
need SROA to recognize that it can split up those arrays and structs
into separate vectors, even though they are not always accessed with
the same type.  SROA already handles loads and stores of an entire
alloca by using insertvalue/extractvalue to access the individual
pieces, and that code works the same regardless of whether the type
is a struct or an array.  So, all that needs to be done is to check
for compatible arrays and homogeneous structs.

llvm-svn: 123381

SROA only split up structs and arrays one level at a time, so padding can
only cause trouble if it is located in between the struct or array elements.

llvm-svn: 123380

llvm-svn: 123318

llvm-svn: 123302

of the bootstrap miscompare issue.

llvm-svn: 123299

the source of the bootstrap problem.

llvm-svn: 123298

llvm-svn: 123288

DT->changeImmediateDominator() trivially ignores identity updates, so there is
really no need for the uniqueing provided by SmallPtrSet.

I expect this to fix PR8954.

llvm-svn: 123286

once at the beginning of GVN instead of once per iteration.

llvm-svn: 123278

llvm-svn: 123270

llvm-svn: 123248

llvm-svn: 123247

Factor the actual simplification out of SimplifyIndirectBrOnSelect and into a new helper function so it can be reused in e.g. an upcoming SimplifySwitchOnSelect.
No functional change.

llvm-svn: 123234

actually reached in the testcase in PR8954, but it's safe and good
practice.

llvm-svn: 123224

is floating around in the ether.

llvm-svn: 123223

phi nodes.  It is called from MergeBlockIntoPredecessor which is 
called from GVN, which claims to preserve these.

I'm skeptical that this is the actual problem behind PR8954, but
this is a stab in the right direction.

llvm-svn: 123222

llvm-svn: 123221

neccesarily an uncond branch to the header.  This fixes 
PR8955 (the assertion tripping).

llvm-svn: 123219

Fix a random missed optimization by making InstCombine more aggressive when determining which bits are demanded by
a comparison against a constant.

llvm-svn: 123203

intrinsics element dependencies. Reviewed by Nick.

llvm-svn: 123161

llvm-svn: 123149

back to life.

llvm-svn: 123146

llvm-svn: 123144

without informing memdep.  This could cause nondeterminstic weirdness 
based on where instructions happen to get allocated, and will hopefully
breath some life into some broken testers.

llvm-svn: 123124

llvm-svn: 123121

llvm-svn: 123117

that have the bit set.

llvm-svn: 123104

updating memdep when fusing stores together.  This fixes the crash optimizing
the bullet benchmark.

llvm-svn: 123091

llvm-svn: 123090

larger memsets.  Among other things, this fixes rdar://8760394 and
allows us to handle "Example 2" from http://blog.regehr.org/archives/320,
compiling it into a single 4096-byte memset:

_mad_synth_mute:                        ## @mad_synth_mute
## BB#0:                                ## %entry
	pushq	%rax
	movl	$4096, %esi             ## imm = 0x1000
	callq	___bzero
	popq	%rax
	ret

llvm-svn: 123089

P and P+1 are relative to the same base pointer.

llvm-svn: 123087

memset into a single larger memset.

llvm-svn: 123086

Split memset formation logic out into its own
"tryMergingIntoMemset" helper function.

llvm-svn: 123081

to be foldable into an uncond branch.  When this happens, we can make a
much simpler CFG for the loop, which is important for nested loop cases
where we want the outer loop to be aggressively optimized.

Handle this case more aggressively.  For example, previously on
phi-duplicate.ll we would get this:


define void @test(i32 %N, double* %G) nounwind ssp {
entry:
  %cmp1 = icmp slt i64 1, 1000
  br i1 %cmp1, label %bb.nph, label %for.end

bb.nph:                                           ; preds = %entry
  br label %for.body

for.body:                                         ; preds = %bb.nph, %for.cond
  %j.02 = phi i64 [ 1, %bb.nph ], [ %inc, %for.cond ]
  %arrayidx = getelementptr inbounds double* %G, i64 %j.02
  %tmp3 = load double* %arrayidx
  %sub = sub i64 %j.02, 1
  %arrayidx6 = getelementptr inbounds double* %G, i64 %sub
  %tmp7 = load double* %arrayidx6
  %add = fadd double %tmp3, %tmp7
  %arrayidx10 = getelementptr inbounds double* %G, i64 %j.02
  store double %add, double* %arrayidx10
  %inc = add nsw i64 %j.02, 1
  br label %for.cond

for.cond:                                         ; preds = %for.body
  %cmp = icmp slt i64 %inc, 1000
  br i1 %cmp, label %for.body, label %for.cond.for.end_crit_edge

for.cond.for.end_crit_edge:                       ; preds = %for.cond
  br label %for.end

for.end:                                          ; preds = %for.cond.for.end_crit_edge, %entry
  ret void
}

Now we get the much nicer:

define void @test(i32 %N, double* %G) nounwind ssp {
entry:
  br label %for.body

for.body:                                         ; preds = %entry, %for.body
  %j.01 = phi i64 [ 1, %entry ], [ %inc, %for.body ]
  %arrayidx = getelementptr inbounds double* %G, i64 %j.01
  %tmp3 = load double* %arrayidx
  %sub = sub i64 %j.01, 1
  %arrayidx6 = getelementptr inbounds double* %G, i64 %sub
  %tmp7 = load double* %arrayidx6
  %add = fadd double %tmp3, %tmp7
  %arrayidx10 = getelementptr inbounds double* %G, i64 %j.01
  store double %add, double* %arrayidx10
  %inc = add nsw i64 %j.01, 1
  %cmp = icmp slt i64 %inc, 1000
  br i1 %cmp, label %for.body, label %for.end

for.end:                                          ; preds = %for.body
  ret void
}

With all of these recent changes, we are now able to compile:

void foo(char *X) {
 for (int i = 0; i != 100; ++i) 
   for (int j = 0; j != 100; ++j)
     X[j+i*100] = 0;
}

into a single memset of 10000 bytes.  This series of changes
should also be helpful for other nested loop scenarios as well.

llvm-svn: 123079

moving the OrigHeader block anymore: we just merge it away anyway so
its code layout doesn't matter.

llvm-svn: 123077

that it was leaving in loops after rotation (between the original latch
block and the original header.

With this change, it is possible for rotated loops to have just a single
basic block, which is useful.

llvm-svn: 123075

loop info.

llvm-svn: 123074