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e92f8121d4
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Author SHA1 Message Date
Chris Lattner
e92f8121d4 improve switch formation to handle small range 
comparisons formed by comparisons.  For example,
this:

void foo(unsigned x) {
  if (x == 0 || x == 1 || x == 3 || x == 4 || x == 6) 
    bar();
}

compiles into:

_foo:                                   ## @foo
## BB#0:                                ## %entry
	cmpl	$6, %edi
	ja	LBB0_2
## BB#1:                                ## %entry
	movl	%edi, %eax
	movl	$91, %ecx
	btq	%rax, %rcx
	jb	LBB0_3

instead of:

_foo:                                   ## @foo
## BB#0:                                ## %entry
	cmpl	$2, %edi
	jb	LBB0_4
## BB#1:                                ## %switch.early.test
	cmpl	$6, %edi
	ja	LBB0_3
## BB#2:                                ## %switch.early.test
	movl	%edi, %eax
	movl	$88, %ecx
	btq	%rax, %rcx
	jb	LBB0_4

This catches a bunch of cases in GCC, which look like this:

 %804 = load i32* @which_alternative, align 4, !tbaa !0
 %805 = icmp ult i32 %804, 2
 %806 = icmp eq i32 %804, 3
 %or.cond121 = or i1 %805, %806
 %807 = icmp eq i32 %804, 4
 %or.cond124 = or i1 %or.cond121, %807
 br i1 %or.cond124, label %.thread, label %808

turning this into a range comparison.

llvm-svn: 122045
 2010-12-17 06:20:15 +00:00
Dan Gohman
f8949c3d1a Revert r64460. strtol and friends cannot be marked readonly, even with 
a null endptr argument, because they may write to errno.

This fixes a seflhost miscompile observed on Linux targets when TBAA
was enabled.

llvm-svn: 122014
 2010-12-17 01:09:43 +00:00
Frits van Bommel
56dc4fc838 Fix a bug in the loop in JumpThreading::ProcessThreadableEdges() where it could falsely produce a MultipleDestSentinel value if the first predecessor ended with an 'indirectbr'. If that happened, it caused an unnecessary FindMostPopularDest() call. 
This wasn't a correctness problem, but it broke the fast path for single-predecessor blocks.

llvm-svn: 121966
 2010-12-16 12:16:00 +00:00
Duncan Sands
22de496ae3 Speculatively revert commit 121905 since it looks like it might have broken the 
dragonegg self-host buildbot.  Original commit message:

Add an InstCombine transform to recognize instances of manual overflow-safe addition
(performing the addition in a wider type and explicitly checking for overflow), and
fold them down to intrinsics.  This currently only supports signed-addition, but could
be generalized if someone works out the magic constant formulas for other operations.

llvm-svn: 121965
 2010-12-16 09:40:54 +00:00
Dan Gohman
e106936414 Make memcpyopt TBAA-aware. 
llvm-svn: 121944
 2010-12-16 02:51:19 +00:00
Dan Gohman
a2fd4f2e22 Preserve TBAA tags when doing load PRE. 
llvm-svn: 121921
 2010-12-15 23:53:55 +00:00
Owen Anderson
aefeb448a9 Add an InstCombine transform to recognize instances of manual overflow-safe addition 
(performing the addition in a wider type and explicitly checking for overflow), and
fold them down to intrinsics.  This currently only supports signed-addition, but could
be generalized if someone works out the magic constant formulas for other operations.

Fixes <rdar://problem/8558713>.

llvm-svn: 121905
 2010-12-15 22:32:38 +00:00
Dan Gohman
295ba3ab26 Move Value::getUnderlyingObject to be a standalone 
function so that it can live in Analysis instead of
VMCore.

llvm-svn: 121885
 2010-12-15 20:02:24 +00:00
Duncan Sands
2699fb1072 Move Sub simplifications and additional Add simplifications out of 
instcombine and into InstructionSimplify.

llvm-svn: 121861
 2010-12-15 14:07:39 +00:00
Frits van Bommel
83b7c3773f Teach jump threading to "look through" a select when the branch direction of a terminator depends on it. 
When it sees a promising select it now tries to figure out whether the condition of the select is known in any of the predecessors and if so it maps the operands appropriately.

llvm-svn: 121859
 2010-12-15 09:51:20 +00:00
Chris Lattner
1499119975 make qsort predicate more conformant by returning 0 for equal values. 
llvm-svn: 121838
 2010-12-15 04:52:41 +00:00
Owen Anderson
de42e1136e Fix PR8790, another instance where unreachable code can cause instruction simplification to fail, 
this case involve a select that simplifies to itself.

llvm-svn: 121817
 2010-12-15 00:55:35 +00:00
Owen Anderson
df08ec80df Cleanup trailing whitespace. 
llvm-svn: 121816
 2010-12-15 00:52:44 +00:00
Chris Lattner
c1aaf52608 - Insert new instructions before DomBlock's terminator, 
which is simpler than finding a place to insert in BB.
 - Don't perform the 'if condition hoisting' xform on certain
   i1 PHIs, as it interferes with switch formation.

This re-fixes "example 7", without breaking the world hopefully.

llvm-svn: 121764
 2010-12-14 08:46:09 +00:00
Chris Lattner
22d4dc5a4d fix two significant issues with FoldTwoEntryPHINode: 
first, it can kick in on blocks whose conditions have been
folded to a constant, even though one of the edges will be
trivially folded.

second, it doesn't clean up the "if diamond" that it just 
eliminated away.  This is a problem because other simplifycfg
xforms kick in depending on the order of block visitation,
causing pointless work.

llvm-svn: 121762
 2010-12-14 08:01:53 +00:00
Chris Lattner
362f9a82c0 remove the instsimplify logic I added in r121754. It is apparently 
breaking the selfhost builds, though I can't fathom how.

llvm-svn: 121761
 2010-12-14 07:53:03 +00:00
Chris Lattner
c2e42269ae clean up logic, convert std::set to SmallPtrSet, handle the case 
when all 2-entry phis are simplified away.

llvm-svn: 121760
 2010-12-14 07:41:39 +00:00
Chris Lattner
8e4194276b tidy up a bit, move DEBUG down to when we commit to doing the transform so we 
don't print it unless the xform happens.

llvm-svn: 121758
 2010-12-14 07:23:10 +00:00
Chris Lattner
811462b2f4 use SimplifyInstruction instead of reimplementing part of it. 
llvm-svn: 121757
 2010-12-14 07:20:29 +00:00
Chris Lattner
e2400eb801 simplify GetIfCondition by using getSinglePredecessor. 
llvm-svn: 121756
 2010-12-14 07:15:21 +00:00
Chris Lattner
8ea88e66dd use AddPredecessorToBlock in 3 places instead of a manual loop. 
llvm-svn: 121755
 2010-12-14 07:09:42 +00:00
Chris Lattner
a87ac36a54 make FoldTwoEntryPHINode use instsimplify a bit, make 
GetIfCondition faster by avoiding pred_iterator.  No
really interesting change.

llvm-svn: 121754
 2010-12-14 07:00:00 +00:00
Chris Lattner
027d572664 remove the dead (and terrible) llvm::RemoveSuccessor function. 
llvm-svn: 121753
 2010-12-14 06:51:55 +00:00
Chris Lattner
d9436ab7d7 improve DEBUG's a bit, switch to eraseFromParent() to simplify 
code a bit, switch from constant folding to instsimplify.

llvm-svn: 121751
 2010-12-14 06:17:25 +00:00
Chris Lattner
093b5b256d reapply my recent change that disables a piece of the switch formation 
work, but fixes 400.perlbmk.

llvm-svn: 121749
 2010-12-14 05:57:30 +00:00
Owen Anderson
5536134dc4 Fix recent buildbot breakage by pulling SimplifyCFG back to its state as of r121694, the most recent state 
where I'm confident there were no crashes or miscompilations.  XFAIL the test added since then for now.

llvm-svn: 121733
 2010-12-13 23:49:28 +00:00
Chris Lattner
dcba81d96f temporarily disable part of my previous patch, which causes an iterator invalidation issue, causing a crash on some versions of perlbmk. 
llvm-svn: 121728
 2010-12-13 23:02:19 +00:00
Chris Lattner
759d8aa712 add some DEBUG's. 
llvm-svn: 121711
 2010-12-13 19:55:30 +00:00
Benjamin Kramer
7f1cdac1e4 Fix sort predicate. qsort(3)'s predicate semantics differ from std::sort's. Fixes PR 8780. 
llvm-svn: 121705
 2010-12-13 18:20:38 +00:00
Chris Lattner
0368bf7457 reinstate my patch: the miscompile was caused by an inverted branch in the 
'and' case.

llvm-svn: 121695
 2010-12-13 08:12:19 +00:00
Chris Lattner
caad324345 Completely disable the optimization I added in r121680 until 
I can track down a miscompile.  This should bring the buildbots
back to life

llvm-svn: 121693
 2010-12-13 07:41:29 +00:00
Chris Lattner
5ce3e42d80 Make simplifycfg reprocess newly formed "br (cond1 | cond2)" conditions 
when simplifying, allowing them to be eagerly turned into switches.  This
is the last step required to get "Example 7" from this blog post:
http://blog.regehr.org/archives/320

On X86, we now generate this machine code, which (to my eye) seems better
than the ICC generated code:

_crud:                                  ## @crud
## BB#0:                                ## %entry
	cmpb	$33, %dil
	jb	LBB0_4
## BB#1:                                ## %switch.early.test
	addb	$-34, %dil
	cmpb	$58, %dil
	ja	LBB0_3
## BB#2:                                ## %switch.early.test
	movzbl	%dil, %eax
	movabsq	$288230376537592865, %rcx ## imm = 0x400000017001421
	btq	%rax, %rcx
	jb	LBB0_4
LBB0_3:                                 ## %lor.rhs
	xorl	%eax, %eax
	ret
LBB0_4:                                 ## %lor.end
	movl	$1, %eax
	ret

llvm-svn: 121690
 2010-12-13 07:00:06 +00:00
Chris Lattner
20b9e84c7e make this logic a bit simpler. 
llvm-svn: 121689
 2010-12-13 06:36:51 +00:00
Chris Lattner
74d917e19d split all the guts of SimplifyCFGOpt::run out into one function 
per terminator kind.

llvm-svn: 121688
 2010-12-13 06:25:44 +00:00
Chris Lattner
ea15ce73be fix a bug in r121680 that upset the various buildbots. 
llvm-svn: 121687
 2010-12-13 05:34:18 +00:00
Chris Lattner
1eb2e235c8 refactor the speculative execution logic to be factored into the cond branch code instead of 
doing a cfg search for every block simplified.

llvm-svn: 121686
 2010-12-13 05:26:52 +00:00
Chris Lattner
4b9e3a31b0 simplify a bunch of code. 
llvm-svn: 121685
 2010-12-13 05:20:28 +00:00
Chris Lattner
d79dd057bf move HoistThenElseCodeToIf up to a more logical and efficient-to-handle place. 
llvm-svn: 121684
 2010-12-13 05:15:29 +00:00
Chris Lattner
80f8577d74 move 'MergeBlocksIntoPredecessor' call earlier. Use 
getSinglePredecessor to simplify code.

llvm-svn: 121683
 2010-12-13 05:10:48 +00:00
Chris Lattner
7ad8e06c3b factor new code out to a SimplifyBranchOnICmpChain helper function. 
llvm-svn: 121681
 2010-12-13 05:03:41 +00:00
Chris Lattner
5cbbcc56ad enhance the "change or icmp's into switch" xform to handle one value in an 
'or sequence' that it doesn't understand.  This allows us to optimize
something insane like this:

int crud (unsigned char c, unsigned x)
 {
   if(((((((((( (int) c <= 32 ||
                    (int) c == 46) || (int) c == 44)
                  || (int) c == 58) || (int) c == 59) || (int) c == 60)
               || (int) c == 62) || (int) c == 34) || (int) c == 92)
            || (int) c == 39) != 0)
     foo();
 }

into:

define i32 @crud(i8 zeroext %c, i32 %x) nounwind ssp noredzone {
entry:
  %cmp = icmp ult i8 %c, 33
  br i1 %cmp, label %if.then, label %switch.early.test

switch.early.test:                                ; preds = %entry
  switch i8 %c, label %if.end [
    i8 39, label %if.then
    i8 44, label %if.then
    i8 58, label %if.then
    i8 59, label %if.then
    i8 60, label %if.then
    i8 62, label %if.then
    i8 46, label %if.then
    i8 92, label %if.then
    i8 34, label %if.then
  ]

by pulling the < comparison out ahead of the newly formed switch.

llvm-svn: 121680
 2010-12-13 04:50:38 +00:00
Chris Lattner
f6be61e969 merge two very similar functions into one that has a bool argument. 
llvm-svn: 121678
 2010-12-13 04:26:26 +00:00
Chris Lattner
003b79e2d3 don't bother handling non-canonical icmp's 
llvm-svn: 121676
 2010-12-13 04:18:32 +00:00
Chris Lattner
9bd0b12342 inline a function, making the result much simpler. 
llvm-svn: 121675
 2010-12-13 04:15:19 +00:00
Chris Lattner
25b642edfd Fix my previous patch to handle a degenerate case that the llvm-gcc 
bootstrap buildbot tripped over.

llvm-svn: 121674
 2010-12-13 03:43:57 +00:00
Chris Lattner
9b089512e9 convert some methods to be static functions 
llvm-svn: 121673
 2010-12-13 03:30:12 +00:00
Chris Lattner
46cc5158bb zap two more std::sorts. 
llvm-svn: 121672
 2010-12-13 03:24:30 +00:00
Chris Lattner
a21c02e807 fix a fairly serious oversight with switch formation from 
or'd conditions.  Previously we'd compile something like this:

int crud (unsigned char c) {
   return c == 62 || c == 34 || c == 92;
}

into:

  switch i8 %c, label %lor.rhs [
    i8 62, label %lor.end
    i8 34, label %lor.end
  ]

lor.rhs:                                          ; preds = %entry
  %cmp8 = icmp eq i8 %c, 92
  br label %lor.end

lor.end:                                          ; preds = %entry, %entry, %lor.rhs
  %0 = phi i1 [ true, %entry ], [ %cmp8, %lor.rhs ], [ true, %entry ]
  %lor.ext = zext i1 %0 to i32
  ret i32 %lor.ext

which failed to merge the compare-with-92 into the switch.  With this patch
we simplify this all the way to:

  switch i8 %c, label %lor.rhs [
    i8 62, label %lor.end
    i8 34, label %lor.end
    i8 92, label %lor.end
  ]

lor.rhs:                                          ; preds = %entry
  br label %lor.end

lor.end:                                          ; preds = %entry, %entry, %entry, %lor.rhs
  %0 = phi i1 [ true, %entry ], [ false, %lor.rhs ], [ true, %entry ], [ true, %entry ]
  %lor.ext = zext i1 %0 to i32
  ret i32 %lor.ext

which is much better for codegen's switch lowering stuff.  This kicks in 33 times
on 176.gcc (for example) cutting 103 instructions off the generated code.

llvm-svn: 121671
 2010-12-13 03:18:54 +00:00
Chris Lattner
6d4df726a6 simplify code and reduce indentation 
llvm-svn: 121670
 2010-12-13 02:38:13 +00:00
Chris Lattner
134d892049 convert an std::sort to array_pod_sort. 
llvm-svn: 121669
 2010-12-13 02:00:58 +00:00