Commit Graph

12 Commits

Author SHA1 Message Date
Sanjay Patel 9ad8fb68f7 [InstSimplify] analyze (optionally casted) icmps to eliminate obviously false logic (PR27869)
By moving this transform to InstSimplify from InstCombine, we sidestep the problem/question
raised by PR27869:
https://llvm.org/bugs/show_bug.cgi?id=27869
...where InstCombine turns an icmp+zext into a shift causing us to miss the fold.

Credit to David Majnemer for a draft patch of the changes to InstructionSimplify.cpp.

Differential Revision: http://reviews.llvm.org/D21512

llvm-svn: 273200
2016-06-20 20:59:59 +00:00
Sanjay Patel a4b052c7d1 [InstSimplify] add tests for PR27689; regenerate checks
llvm-svn: 273128
2016-06-19 21:40:12 +00:00
Sanjay Patel 69632447b1 [InstSimplify] regenerate checks using a script
I didn't notice any significant changes in the actual checks here;
all of these tests already used FileCheck, so a script can batch
update them in one shot.

This commit is just to show the value of automating this process: 
We have uniform formatting as opposed to a mish-mash of check
structure that changes based on individual prefs and the current
fashion. This makes it simpler to update when we find a bug or
make an enhancement.

llvm-svn: 264457
2016-03-25 20:12:25 +00:00
David Majnemer d5b3aa49ac InstSimplify: Try to bring back the rest of r223583
This reverts r223624 with a small tweak, hopefully this will make stage3
equivalent.

llvm-svn: 223679
2014-12-08 18:30:43 +00:00
NAKAMURA Takumi 2b6e662672 Revert a part of r223583, for now. It seems causing different emission between stage2(gcc-clang) and stage3 clang. Investigating.
llvm-svn: 223624
2014-12-08 02:07:22 +00:00
David Majnemer 1af36e5baf InstSimplify: Optimize away useless unsigned comparisons
Code like X < Y && Y == 0 should always be folded away to false.

llvm-svn: 223583
2014-12-06 10:51:40 +00:00
David Majnemer 4efa9ff8ca InstSimplify: Simplify (sub 0, X) -> X if it's NUW
This is a generalization of the X - (0 - Y) -> X transform.

llvm-svn: 222611
2014-11-22 07:15:16 +00:00
David Majnemer a315bd80c2 InstSimplify: Simplify trivial and/or of icmps
Some ICmpInsts when anded/ored with another ICmpInst trivially reduces
to true or false depending on whether or not all integers or no integers
satisfy the intersected/unioned range.

This sort of trivial looking code can come about when InstCombine
performs a range reduction-type operation on sdiv and the like.

This fixes PR20916.

llvm-svn: 217750
2014-09-15 08:15:28 +00:00
David Majnemer cd4fbcd1bb InstSimplify: Simplify (X - (0 - Y)) if the second sub is NUW
If the NUW bit is set for 0 - Y, we know that all values for Y other
than 0 would produce a poison value.  This allows us to replace (0 - Y)
with 0 in the expression (X - (0 - Y)) which will ultimately leave us
with X.

This partially fixes PR20189.

llvm-svn: 214384
2014-07-31 04:49:18 +00:00
Stephen Lin c1c7a1309c Update Transforms tests to use CHECK-LABEL for easier debugging. No functionality change.
This update was done with the following bash script:

  find test/Transforms -name "*.ll" | \
  while read NAME; do
    echo "$NAME"
    if ! grep -q "^; *RUN: *llc" $NAME; then
      TEMP=`mktemp -t temp`
      cp $NAME $TEMP
      sed -n "s/^define [^@]*@\([A-Za-z0-9_]*\)(.*$/\1/p" < $NAME | \
      while read FUNC; do
        sed -i '' "s/;\(.*\)\([A-Za-z0-9_]*\):\( *\)@$FUNC\([( ]*\)\$/;\1\2-LABEL:\3@$FUNC(/g" $TEMP
      done
      mv $TEMP $NAME
    fi
  done

llvm-svn: 186268
2013-07-14 01:42:54 +00:00
Duncan Sands 985ba6386d A shift of a power of two is a power of two or zero.
For completeness - not spotted in the wild.

llvm-svn: 143211
2011-10-28 18:30:05 +00:00
Duncan Sands ba286d7c73 The maximum power of 2 dividing a power of 2 is itself. This occurs
in 403.gcc and was spotted by my super-optimizer.

llvm-svn: 143054
2011-10-26 20:55:21 +00:00