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123 Commits

Author SHA1 Message Date
Benjamin Kramer
04249128ab SimplifyCFG: Track the number of used icmps when turning a icmp chain into a switch. If we used only one icmp, don't turn it into a switch. 
Also prevent the switch-to-icmp transform from creating identity adds, noticed by Marius Wachtler.

llvm-svn: 125056
 2011-02-07 22:37:28 +00:00
Benjamin Kramer
75785ec972 SimplifyCFG: Also transform switches that represent a range comparison but are not sorted into sub+icmp. 
This transforms another 1000 switches in gcc.c.

llvm-svn: 124826
 2011-02-03 22:51:41 +00:00
Benjamin Kramer
b739613711 SimplifyCFG: Turn switches into sub+icmp+branch if possible. 
This makes the job of the later optzn passes easier, allowing the vast amount of
icmp transforms to chew on it.

We transform 840 switches in gcc.c, leading to a 16k byte shrink of the resulting
binary on i386-linux.

The testcase from README.txt now compiles into
  decl  %edi
  cmpl  $3, %edi
  sbbl  %eax, %eax
  andl  $1, %eax
  ret

llvm-svn: 124724
 2011-02-02 15:56:22 +00:00
Evan Cheng
4af5487b74 Re-apply r124518 with fix. Watch out for invalidated iterator. 
llvm-svn: 124526
 2011-01-29 04:46:23 +00:00
Evan Cheng
1f943b9b13 Revert r124518. It broke Linux self-host. 
llvm-svn: 124522
 2011-01-29 02:43:04 +00:00
Evan Cheng
a1e4cb5f09 Re-commit r124462 with fixes. Tail recursion elim will now dup ret into unconditional predecessor to enable TCE on demand. 
llvm-svn: 124518
 2011-01-29 01:29:26 +00:00
Evan Cheng
5b6c72e549 Revert r124462. There are a few big regressions that I need to fix first. 
llvm-svn: 124478
 2011-01-28 07:12:38 +00:00
Evan Cheng
7031f450b3 - Stop simplifycfg from duplicating "ret" instructions into unconditional 
branches. PR8575, rdar://5134905, rdar://8911460.
- Allow codegen tail duplication to dup small return blocks after register
  allocation is done.

llvm-svn: 124462
 2011-01-28 02:19:21 +00:00
Benjamin Kramer
39b30b18fa SimplifyCFG: Ranges can be larger than 64 bits. Fixes Release-selfhost build. 
llvm-svn: 122054
 2010-12-17 10:48:14 +00:00
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
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
5d4aea9791 fix yet anohter broken line 
llvm-svn: 121750
 2010-12-14 06:09:07 +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
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
ea15ce73be fix a bug in r121680 that upset the various buildbots. 
llvm-svn: 121687
 2010-12-13 05:34:18 +00:00
Chris Lattner
c331eb8e1e make these tests a bit less fragile 
llvm-svn: 121682
 2010-12-13 05:10:30 +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
e35f4b31f4 merge two tests 
llvm-svn: 121679
 2010-12-13 04:45:56 +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
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
Frits van Bommel
31cf7b99f9 Teach SimplifyCFG to turn 
(indirectbr (select cond, blockaddress(@fn, BlockA),
                            blockaddress(@fn, BlockB)))
into
  (br cond, BlockA, BlockB).

llvm-svn: 120943
 2010-12-05 18:29:03 +00:00
Dan Gohman
b20b7d2ec2 Factor out Instruction::isSafeToSpeculativelyExecute's code for 
testing for dereferenceable pointers into a helper function,
isDereferenceablePointer.  Teach it how to reason about GEPs
with simple non-zero indices.

Also eliminate ArgumentPromtion's IsAlwaysValidPointer,
which didn't check for weak externals or out of range gep
indices.

llvm-svn: 118840
 2010-11-11 21:23:25 +00:00
Duncan Sands
5b25503aab Fix PR8445: a block with no predecessors may be the entry block, in which case 
it isn't unreachable and should not be zapped.  The check for the entry block
was missing in one case: a block containing a unwind instruction.  While there,
do some small cleanups: "M" is not a great name for a Function* (it would be
more appropriate for a Module*), change it to "Fn"; use Fn in more places.

llvm-svn: 117224
 2010-10-24 12:23:30 +00:00
Duncan Sands
254f8ff0a6 Correct bogus module triple specifications. 
llvm-svn: 112469
 2010-08-30 10:48:29 +00:00
Dan Gohman
9178d0792f Instead, teach SimplifyCFG to trim non-address-taken blocks from 
indirectbr destination lists.

llvm-svn: 111122
 2010-08-16 14:41:14 +00:00
Dan Gohman
d04a608a73 Teach SimplifyCFG how to simplify indirectbr instructions. 
- Eliminate redundant successors.
 - Convert an indirectbr with one successor into a direct branch.

Also, generalize SimplifyCFG to be able to be run on a function entry block.
It knows quite a few simplifications which are applicable to the entry
block, and it only needs a few checks to avoid trouble with the entry block.

llvm-svn: 111060
 2010-08-14 00:29:42 +00:00
Benjamin Kramer
443f74025b Test case for r105914. 
llvm-svn: 105915
 2010-06-13 16:16:54 +00:00
Chris Lattner
e74d980a02 make simplifycfg insert an llvm.trap before the 'unreachable' it introduces 
when it detects undefined behavior.  llvm.trap generally codegens into some
thing really small (e.g. a 2 byte ud2 instruction on x86) and debugging this
sort of thing is "nontrivial".  For example, we now compile:

void foo() { *(int*)0 = 42; }

into:

_foo:
	pushl	%ebp
	movl	%esp, %ebp
	ud2

Some may even claim that this is a security hole, though that seems dubious
to me.  This addresses rdar://7958343 - Optimizing away null dereference 
potentially allows arbitrary code execution

llvm-svn: 103356
 2010-05-08 22:15:59 +00:00
Gabor Greif
b7ecfb134b testcase for r99914, provided by baldrick! 
llvm-svn: 100043
 2010-03-31 20:37:13 +00:00
Dan Gohman
37bf232609 Floating-point add, sub, and mul are now spelled fadd, fsub, and fmul, 
respectively.

llvm-svn: 97531
 2010-03-02 01:11:08 +00:00
Jakob Stoklund Olesen
670458b3be Teach SimplifyCFG about magic pointer constants. 
Weird code sometimes uses pointer constants other than null. This patch
teaches SimplifyCFG to build switch instructions in those cases.

Code like this:

void f(const char *x) {
  if (!x)
    puts("null");
  else if ((uintptr_t)x == 1)
    puts("one");
  else if (x == (char*)2 || x == (char*)3)
    puts("two");
  else if ((intptr_t)x == 4)
    puts("four");
  else
    puts(x);
}

Now becomes a switch:

define void @f(i8* %x) nounwind ssp {
entry:
  %magicptr23 = ptrtoint i8* %x to i64            ; <i64> [#uses=1]
  switch i64 %magicptr23, label %if.else16 [
    i64 0, label %if.then
    i64 1, label %if.then2
    i64 2, label %if.then9
    i64 3, label %if.then9
    i64 4, label %if.then14
  ]

Note that LLVM's own DenseMap uses magic pointers.

llvm-svn: 95439
 2010-02-05 22:03:18 +00:00
Dan Gohman
5fa04f2707 Delete useless trailing semicolons. 
llvm-svn: 92740
 2010-01-05 17:55:26 +00:00
Chris Lattner
83d5230121 fix two bogus tests that the asmparser now rejects. 
llvm-svn: 92303
 2009-12-30 05:54:51 +00:00
Chris Lattner
4e30207029 Implement PR5795 by merging duplicated return blocks. This could go further 
by merging all returns in a function into a single one, but simplifycfg 
currently likes to duplicate the return (an unfortunate choice!)

llvm-svn: 91890
 2009-12-22 06:07:30 +00:00
Chris Lattner
3f9fc699e0 convert to filecheck 
llvm-svn: 91889
 2009-12-22 06:04:26 +00:00
Dan Gohman
d7b00c4c8d Optimize test more. 
llvm-svn: 86714
 2009-11-10 21:02:18 +00:00
Chris Lattner
3455c2f5c6 optimize test 
llvm-svn: 86672
 2009-11-10 07:44:36 +00:00
Dan Gohman
61e806613f Revert r85667. LoopUnroll currently can't call utility functions which 
auto-update the DominatorTree because it doesn't keep the DominatorTree
current while it works.

llvm-svn: 85670
 2009-10-31 17:33:01 +00:00
Dan Gohman
40cec16be1 Merge the enhancements from LoopUnroll's FoldBlockIntoPredecessor into 
MergeBlockIntoPredecessor. This makes SimplifyCFG slightly more aggressive,
and makes it unnecessary for LoopUnroll to have its own copy of this code.

llvm-svn: 85667
 2009-10-31 16:08:00 +00:00
Dan Gohman
cd411a597d Add a testcase for the recent duplicate PHI elimination changes. 
llvm-svn: 85636
 2009-10-30 23:16:10 +00:00
Chris Lattner
3982885b51 if basic blocks are destroyed while there are *just* BlockAddress' hanging 
around, then zap them.  This is analogous to dangling constantexprs hanging
off functions.

llvm-svn: 85627
 2009-10-30 22:39:36 +00:00
Chris Lattner
26c670aa44 change simplifycfg to not duplicate 'unwind' instructions. Hopefully 
this will increase the likelihood of common code getting sunk towards
the unwind.

llvm-svn: 83996
 2009-10-13 18:13:05 +00:00
Chris Lattner
f5049b6bb8 convert to filecheck 
llvm-svn: 83995
 2009-10-13 18:10:05 +00:00
Chris Lattner
8ddeaf680a rename test 
llvm-svn: 83994
 2009-10-13 18:08:21 +00:00