Commit Graph

3 Commits

Author SHA1 Message Date
Joey Gouly
6ef4dd8cb6 Fix a bug in InstCombine where it attempted to cast a Value* to an Instruction*
when it was actually a Constant*.

There are quite a few other casts to Instruction that might have the same problem,
but this is the only one I have a test case for.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191668 91177308-0d34-0410-b5e6-96231b3b80d8
2013-09-30 14:18:35 +00:00
Stephen Lin
39f4e8d9cc 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


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186268 91177308-0d34-0410-b5e6-96231b3b80d8
2013-07-14 01:42:54 +00:00
Shuxin Yang
a1444219b2 1. Hoist minus sign as high as possible in an attempt to reveal
some optimization opportunities (in the enclosing supper-expressions).

   rule 1. (-0.0 - X ) * Y => -0.0 - (X * Y)
     if expression "-0.0 - X" has only one reference.

   rule 2. (0.0 - X ) * Y => -0.0 - (X * Y)
     if expression "0.0 - X" has only one reference, and
        the instruction is marked "noSignedZero".

2. Eliminate negation (The compiler was already able to handle these
    opt if the 0.0s are replaced with -0.0.)

   rule 3: (0.0 - X) * (0.0 - Y) => X * Y
   rule 4: (0.0 - X) * C => X * -C
   if the expr is flagged "noSignedZero".

3. 
  Rule 5: (X*Y) * X => (X*X) * Y
   if X!=Y and the expression is flagged with "UnsafeAlgebra".

   The purpose of this transformation is two-fold:
    a) to form a power expression (of X).
    b) potentially shorten the critical path: After transformation, the
       latency of the instruction Y is amortized by the expression of X*X,
       and therefore Y is in a "less critical" position compared to what it
      was before the transformation. 

4. Remove the InstCombine code about simplifiying "X * select".
   
   The reasons are following:
    a) The "select" is somewhat architecture-dependent, therefore the
       higher level optimizers are not able to precisely predict if
       the simplification really yields any performance improvement
       or not.

    b) The "select" operator is bit complicate, and tends to obscure
       optimization opportunities. It is btter to keep it as low as
       possible in expr tree, and let CodeGen to tackle the optimization.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172551 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-15 21:09:32 +00:00