Commit Graph

5 Commits

Author SHA1 Message Date
Sanjay Patel 0d4fd5b668 [InstSimplify] fold sdiv/srem based on compare of dividend and divisor
This should bring signed div/rem analysis up to the same level as unsigned. 
We use icmp simplification to determine when the divisor is known greater than the dividend.

Each positive test is followed by a negative test to show that we're not overstepping the boundaries of the known bits.
There are extra tests for the signed-min-value special cases.

Alive proofs:
http://rise4fun.com/Alive/WI5

Differential Revision: https://reviews.llvm.org/D37713

llvm-svn: 313264
2017-09-14 14:59:07 +00:00
Sanjay Patel dc3002de9d [InstSimplify] regenerate checks; NFC
llvm-svn: 313161
2017-09-13 17:39:39 +00:00
David Majnemer cb9d596655 InstCombine, InstSimplify: (%X /s C1) /s C2 isn't always 0 when C1 * C2 overflow
consider:
C1 = INT_MIN
C2 = -1

C1 * C2 overflows without a doubt but consider the following:
%x = i32 INT_MIN

This means that (%X /s C1) is 1 and (%X /s C1) /s C2 is -1.

N. B.  Move the unsigned version of this transform to InstSimplify, it
doesn't create any new instructions.

This fixes PR21243.

llvm-svn: 219567
2014-10-11 10:20:01 +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
Chris Lattner 9e4aa0259f Teach instsimplify some tricks about exact/nuw/nsw shifts.
improve interfaces to instsimplify to take this info.

llvm-svn: 125196
2011-02-09 17:15:04 +00:00