6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-02-08 06:32:24 +00:00
Code Issues Projects Releases Wiki Activity

Treat xor of signbit like an add.

Browse Source 
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35586 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2007-04-02 05:41:38 +00:00
parent febabcc02a
commit 2811f2a670
1 changed files with 10 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
lib/Analysis/ScalarEvolution.cpp
View File

@ -1427,7 +1427,16 @@ SCEVHandle ScalarEvolutionsImpl::createSCEV(Value *V) {
}
}
break;
case Instruction::Xor:
// If the RHS of the xor is a signbit, then this is just an add.
// Instcombine turns add of signbit into xor as a strength reduction step.
if (ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1))) {
if (CI->getValue().isSignBit())
return SCEVAddExpr::get(getSCEV(I->getOperand(0)),
getSCEV(I->getOperand(1)));
}
break;
case Instruction::Shl:
// Turn shift left of a constant amount into a multiply.
if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {