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6 Commits

Author SHA1 Message Date
Chandler Carruth 6b0e34c445 Manually upgrade the test suite to specify the flag to cttz and ctlz. 
I followed three heuristics for deciding whether to set 'true' or
'false':

- Everything target independent got 'true' as that is the expected
  common output of the GCC builtins.
- If the target arch only has one way of implementing this operation,
  set the flag in the way that exercises the most of codegen. For most
  architectures this is also the likely path from a GCC builtin, with
  'true' being set. It will (eventually) require lowering away that
  difference, and then lowering to the architecture's operation.
- Otherwise, set the flag differently dependending on which target
  operation should be tested.

Let me know if anyone has any issue with this pattern or would like
specific tests of another form. This should allow the x86 codegen to
just iteratively improve as I teach the backend how to differentiate
between the two forms, and everything else should remain exactly the
same.

llvm-svn: 146370
 2011-12-12 11:59:10 +00:00
Benjamin Kramer d121765e64 InstCombine: Turn icmp + sext into bitwise/integer ops when the input has only one unknown bit. 
int test1(unsigned x) { return (x&8) ? 0 : -1; }
int test3(unsigned x) { return (x&8) ? -1 : 0; }

before (x86_64):
_test1:
	andl	$8, %edi
	cmpl	$1, %edi
	sbbl	%eax, %eax
	ret
_test3:
	andl	$8, %edi
	cmpl	$1, %edi
	sbbl	%eax, %eax
	notl	%eax
	ret

after:
_test1:
	shrl	$3, %edi
	andl	$1, %edi
	leal	-1(%rdi), %eax
	ret
_test3:
	shll	$28, %edi
	movl	%edi, %eax
	sarl	$31, %eax
	ret

llvm-svn: 128732
 2011-04-01 20:09:10 +00:00
Benjamin Kramer 391a946fa9 ComputeMaskedBits: sub falls through to add, and sub doesn't have the same overflow semantics as add. 
Should fix the selfhost failures that started with r127463.

llvm-svn: 127465
 2011-03-11 14:46:49 +00:00
Chris Lattner 6b657aed33 Enhance a bunch of transformations in instcombine to start generating 
exact/nsw/nuw shifts and have instcombine infer them when it can prove
that the relevant properties are true for a given shift without them.

Also, a variety of refactoring to use the new patternmatch logic thrown
in for good luck.  I believe that this takes care of a bunch of related
code quality issues attached to PR8862.

llvm-svn: 125267
 2011-02-10 05:36:31 +00:00
Chris Lattner 4ca1981e82 merge sext-2 into sext.ll 
llvm-svn: 90293
 2009-12-02 05:34:35 +00:00
Chris Lattner 0a12a8f9fe rename test 
llvm-svn: 90292
 2009-12-02 05:32:33 +00:00