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Author SHA1 Message Date
David Majnemer 587336d2ad [Reassociate] Canonicalizing 'x [+-] (-Constant * y)' isn't always a win 
Canonicalizing 'x [+-] (-Constant * y)' is not a win if we don't *know*
we will open up CSE opportunities.

If the multiply was 'nsw', then negating 'y' requires us to clear the
'nsw' flag.  If this is actually worth pursuing, it is probably more
appropriate to do so in GVN or EarlyCSE.

This fixes PR23675.

llvm-svn: 238397
 2015-05-28 06:16:39 +00:00
Chad Rosier 90a2f9b110 Revert "[Reassociate] As the expression tree is rewritten make sure the operands are" 
This reverts commit r222142.  This is causing/exposing an execution-time regression
in spec2006/gcc and coremark on AArch64/A57/Ofast.

Conflicts:

	test/Transforms/Reassociate/optional-flags.ll

llvm-svn: 222398
 2014-11-19 23:21:20 +00:00
Chad Rosier bc0b869be9 [Reassociate] As the expression tree is rewritten make sure the operands are 
emitted in canonical form.

llvm-svn: 222142
 2014-11-17 16:33:50 +00:00
Chad Rosier 9a1ac6e494 [Reassociate] Canonicalize constants to RHS operand. 
Fix a thinko where the RHS was already a constant.

llvm-svn: 222139
 2014-11-17 15:52:51 +00:00
Chad Rosier f8b55f1bc5 [Reassociate] Canonicalize constants to RHS operand. 
llvm-svn: 222005
 2014-11-14 17:05:59 +00:00
Chad Rosier f53f07046b [Reassociate] Canonicalize negative constants out of expressions. 
Add support for FDiv, which was regressed by the previous commit.

llvm-svn: 221738
 2014-11-11 23:36:42 +00:00
Chad Rosier 094ac7735b [Reassociate] Canonicalize negative constants out of expressions. 
This is a reapplication of r221171, but we only perform the transformation
on expressions which include a multiplication.  We do not transform rem/div
operations as this doesn't appear to be safe in all cases.

llvm-svn: 221721
 2014-11-11 22:58:35 +00:00
Reid Kleckner 941e93e9a8 Revert "[Reassociate] Canonicalize negative constants out of expressions." 
This reverts commit r221171.

It performs this invalid transformation:
-  %div.i = urem i64 -1, %add
-  %sub.i = sub i64 -2, %div.i
+  %div.i = urem i64 1, %add
+  %sub.i1 = add i64 %div.i, -2

llvm-svn: 221317
 2014-11-04 23:42:45 +00:00
Chad Rosier 005505b027 [Reassociate] Canonicalize negative constants out of expressions. 
This gives CSE/GVN more options to eliminate duplicate expressions.
This is a follow up patch to http://reviews.llvm.org/D4904.

http://reviews.llvm.org/D5363

llvm-svn: 221171
 2014-11-03 19:11:30 +00:00