From 4ee29af754f3b81ce90a5aa8f540b1f4a790191c Mon Sep 17 00:00:00 2001 From: Dan Gohman Date: Tue, 21 Apr 2009 02:26:00 +0000 Subject: [PATCH] Teach ScalarEvolution how to recognize zext-inreg and sext-inreg, as they appear in LLVM IR. This isn't particularly interesting on its own; this is just setting up some infrastructure. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@69655 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Analysis/ScalarEvolution.cpp | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp index 0dbb2580476..ace063a399c 100644 --- a/lib/Analysis/ScalarEvolution.cpp +++ b/lib/Analysis/ScalarEvolution.cpp @@ -1947,6 +1947,19 @@ SCEVHandle ScalarEvolutionsImpl::createSCEV(Value *V) { case Instruction::Sub: return SE.getMinusSCEV(getSCEV(U->getOperand(0)), getSCEV(U->getOperand(1))); + case Instruction::And: + // For an expression like x&255 that merely masks off the high bits, + // use zext(trunc(x)) as the SCEV expression. + if (ConstantInt *CI = dyn_cast(U->getOperand(1))) { + const APInt &A = CI->getValue(); + unsigned Ones = A.countTrailingOnes(); + if (APIntOps::isMask(Ones, A)) + return + SE.getZeroExtendExpr(SE.getTruncateExpr(getSCEV(U->getOperand(0)), + IntegerType::get(Ones)), + U->getType()); + } + break; case Instruction::Or: // If the RHS of the Or is a constant, we may have something like: // X*4+1 which got turned into X*4|1. Handle this as an Add so loop @@ -1996,6 +2009,20 @@ SCEVHandle ScalarEvolutionsImpl::createSCEV(Value *V) { } break; + case Instruction::AShr: + // For a two-shift sext-inreg, use sext(trunc(x)) as the SCEV expression. + if (ConstantInt *CI = dyn_cast(U->getOperand(1))) + if (Instruction *L = dyn_cast(U->getOperand(0))) + if (L->getOpcode() == Instruction::Shl && + L->getOperand(1) == U->getOperand(1)) { + uint64_t Amt = CI->getZExtValue(); + return + SE.getSignExtendExpr(SE.getTruncateExpr(getSCEV(L->getOperand(0)), + IntegerType::get(Amt)), + U->getType()); + } + break; + case Instruction::Trunc: return SE.getTruncateExpr(getSCEV(U->getOperand(0)), U->getType()); -- 2.34.1