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[Reassociate] Similar to "X + -X" -> "0", added code to handle "X + ~X" -> "-1".

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Handle "X + ~X" -> "-1" in the function Value *Reassociate::OptimizeAdd(Instruction *I, SmallVectorImpl<ValueEntry> &Ops);
This patch implements:
TODO: We could handle "X + ~X" -> "-1" if we wanted, since "-X = ~X+1".

Patch by Rahul Jain!

Differential Revision: http://reviews.llvm.org/D3835

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209973 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer 2014-05-31 15:01:54 +00:00
parent da5824d073
commit 37bc2f3216
2 changed files with 35 additions and 8 deletions
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31
lib/Transforms/Scalar/Reassociate.cpp
View File

@ -1368,11 +1368,10 @@ Value *Reassociate::OptimizeXor(Instruction *I,
Value *Reassociate::OptimizeAdd(Instruction *I,
SmallVectorImpl<ValueEntry> &Ops) {
// Scan the operand lists looking for X and -X pairs. If we find any, we
// can simplify the expression. X+-X == 0. While we're at it, scan for any
// can simplify expressions like X+-X == 0 and X+~X ==-1. While we're at it,
// scan for any
// duplicates. We want to canonicalize Y+Y+Y+Z -> 3*Y+Z.
//
// TODO: We could handle "X + ~X" -> "-1" if we wanted, since "-X = ~X+1".
//
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
Value *TheOp = Ops[i].Op;
// Check to see if we've seen this operand before. If so, we factor all
@ -1412,19 +1411,28 @@ Value *Reassociate::OptimizeAdd(Instruction *I,
continue;
}
// Check for X and -X in the operand list.
if (!BinaryOperator::isNeg(TheOp))
// Check for X and -X or X and ~X in the operand list.
if (!BinaryOperator::isNeg(TheOp) && !BinaryOperator::isNot(TheOp))
continue;
Value *X = BinaryOperator::getNegArgument(TheOp);
Value *X = nullptr;
if (BinaryOperator::isNeg(TheOp))
X = BinaryOperator::getNegArgument(TheOp);
else if (BinaryOperator::isNot(TheOp))
X = BinaryOperator::getNotArgument(TheOp);
unsigned FoundX = FindInOperandList(Ops, i, X);
if (FoundX == i)
continue;
// Remove X and -X from the operand list.
if (Ops.size() == 2)
if (Ops.size() == 2 && BinaryOperator::isNeg(TheOp))
return Constant::getNullValue(X->getType());
// Remove X and ~X from the operand list.
if (Ops.size() == 2 && BinaryOperator::isNot(TheOp))
return Constant::getAllOnesValue(X->getType());
Ops.erase(Ops.begin()+i);
if (i < FoundX)
--FoundX;
@ -1434,6 +1442,13 @@ Value *Reassociate::OptimizeAdd(Instruction *I,
++NumAnnihil;
--i; // Revisit element.
e -= 2; // Removed two elements.
// if X and ~X we append -1 to the operand list.
if (BinaryOperator::isNot(TheOp)) {
Value *V = Constant::getAllOnesValue(X->getType());
Ops.insert(Ops.end(), ValueEntry(getRank(V), V));
e += 1;
}
}
// Scan the operand list, checking to see if there are any common factors

12
test/Transforms/Reassociate/inverses.ll
View File

@ -32,3 +32,15 @@ define i32 @test3(i32 %b, i32 %a) {
; CHECK: %tmp.5 = add i32 %b, 1234
; CHECK: ret i32 %tmp.5
}
define i32 @test4(i32 %b, i32 %a) {
%tmp.1 = add i32 %a, 1234
%tmp.2 = add i32 %b, %tmp.1
%tmp.4 = xor i32 %a, -1
; (b+(a+1234))+~a -> b+1233
%tmp.5 = add i32 %tmp.2, %tmp.4
ret i32 %tmp.5
; CHECK-LABEL: @test4(
; CHECK: %tmp.5 = add i32 %b, 1233
; CHECK: ret i32 %tmp.5
}