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INT_NEGATE and SUBPIECE in RuleSless2Zero

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caheckman 2019-07-24 09:56:59 -04:00
parent 9fc99efc93
commit 6e44b809b9
1 changed files with 42 additions and 39 deletions
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81
Ghidra/Features/Decompiler/src/decompile/cpp/ruleaction.cc
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@ -3191,17 +3191,6 @@ int4 RuleTestSign::applyOp(PcodeOp *op,Funcdata &data)
if (val != 8*inVn->getSize() -1) return 0; if (val != 8*inVn->getSize() -1) return 0;
Varnode *outVn = op->getOut(); Varnode *outVn = op->getOut();
// Check if input comes from truncation of larger value
if (inVn->isWritten()) {
PcodeOp *truncOp = inVn->getDef();
if (truncOp->code() == CPUI_SUBPIECE) {
Varnode *newIn = truncOp->getIn(0);
int4 truncAmount = (int4)truncOp->getIn(1)->getOffset();
if (truncAmount + inVn->getSize() == newIn->getSize()) { // If this is the most significant bytes
inVn = newIn; // We are really extracting the sign-bit from a larger value
}
}
}
if (inVn->isFree()) return 0; if (inVn->isFree()) return 0;
vector<PcodeOp *> compareOps; vector<PcodeOp *> compareOps;
findComparisons(outVn, compareOps); findComparisons(outVn, compareOps);
@ -5245,24 +5234,26 @@ Varnode *RuleSLess2Zero::getHiBit(PcodeOp *op)
} }
/// \class RuleSLess2Zero /// \class RuleSLess2Zero
/// \brief Simplify INT_SLESS and INT_SLESSEQUAL applied to 0 or -1 /// \brief Simplify INT_SLESS applied to 0 or -1
/// ///
/// Forms include: /// Forms include:
/// - `0 s< V * -1 => V s< 0` /// - `0 s< V * -1 => V s< 0`
/// - `V * -1 s< 0 => 0 s< V` /// - `V * -1 s< 0 => 0 s< V`
/// - `-1 s< SUB(V,#hi) => -1 s< V`
/// - `SUB(V,#hi) s< 0 => V s< 0`
/// - `-1 s< ~V => V s< 0`
/// - `~V s< 0 => -1 s< V`
/// ///
/// There is a second set of forms where one side of the comparison is /// There is a second set of forms where one side of the comparison is
/// built out of a high and low piece, where the high piece determines the /// built out of a high and low piece, where the high piece determines the
/// sign bit: /// sign bit:
/// - `0 s<= (hi + lo) => 0 s<= hi`
/// - `-1 s< (hi + lo) => -1 s< hi` /// - `-1 s< (hi + lo) => -1 s< hi`
/// - `(hi + lo) s< 0 => hi s< 0` /// - `(hi + lo) s< 0 => hi s< 0`
/// - `(hi + lo) s<= -1 => hi s<= -1` ///
void RuleSLess2Zero::getOpList(vector<uint4> &oplist) const void RuleSLess2Zero::getOpList(vector<uint4> &oplist) const
{ {
oplist.push_back(CPUI_INT_SLESS); oplist.push_back(CPUI_INT_SLESS);
oplist.push_back(CPUI_INT_SLESSEQUAL);
} }
int4 RuleSLess2Zero::applyOp(PcodeOp *op,Funcdata &data) int4 RuleSLess2Zero::applyOp(PcodeOp *op,Funcdata &data)
@ -5287,21 +5278,11 @@ int4 RuleSLess2Zero::applyOp(PcodeOp *op,Funcdata &data)
data.opSetInput(op,lvn,1); data.opSetInput(op,lvn,1);
return 1; return 1;
} }
else if (op->code() == CPUI_INT_SLESSEQUAL) {
Varnode *hibit = getHiBit(multop);
if (hibit != (Varnode *)0) { // Test for 0 s<= (hi ^ lo)
if (hibit->isConstant())
data.opSetInput(op,data.newConstant(hibit->getSize(),hibit->getOffset()),1);
else
data.opSetInput(op,hibit,1);
data.opSetOpcode(op,CPUI_INT_EQUAL);
return 1;
}
}
} }
else if (lvn->getOffset() == calc_mask(lvn->getSize())) { else if (lvn->getOffset() == calc_mask(lvn->getSize())) {
if (op->code() == CPUI_INT_SLESS) { if (op->code() == CPUI_INT_SLESS) {
Varnode *hibit = getHiBit(rvn->getDef()); multop = rvn->getDef();
Varnode *hibit = getHiBit(multop);
if (hibit != (Varnode *)0) { // Test for -1 s< (hi ^ lo) if (hibit != (Varnode *)0) { // Test for -1 s< (hi ^ lo)
if (hibit->isConstant()) if (hibit->isConstant())
data.opSetInput(op,data.newConstant(hibit->getSize(),hibit->getOffset()),1); data.opSetInput(op,data.newConstant(hibit->getSize(),hibit->getOffset()),1);
@ -5311,6 +5292,24 @@ int4 RuleSLess2Zero::applyOp(PcodeOp *op,Funcdata &data)
data.opSetInput(op,data.newConstant(hibit->getSize(),0),0); data.opSetInput(op,data.newConstant(hibit->getSize(),0),0);
return 1; return 1;
} }
else if (multop->code() == CPUI_SUBPIECE) {
avn = multop->getIn(0);
if (avn->isFree()) return 0;
if (avn->getSize() + (int4)multop->getIn(1)->getOffset() == rvn->getSize()) {
// We have -1 s< SUB( avn, #hi )
data.opSetInput(op,avn,1);
data.opSetInput(op,data.newConstant(avn->getSize(),calc_mask(avn->getSize())),0);
return 1;
}
}
else if (multop->code() == CPUI_INT_NEGATE) {
// We have -1 s< ~avn
avn = multop->getIn(0);
if (avn->isFree()) return 0;
data.opSetInput(op,avn,0);
data.opSetInput(op,data.newConstant(avn->getSize(),0),1);
return 1;
}
} }
} }
} }
@ -5338,18 +5337,22 @@ int4 RuleSLess2Zero::applyOp(PcodeOp *op,Funcdata &data)
data.opSetOpcode(op,CPUI_INT_NOTEQUAL); data.opSetOpcode(op,CPUI_INT_NOTEQUAL);
return 1; return 1;
} }
} else if (multop->code() == CPUI_SUBPIECE) {
} avn = multop->getIn(0);
else if (rvn->getOffset() == calc_mask(rvn->getSize())) { if (avn->isFree()) return 0;
if (op->code() == CPUI_INT_SLESSEQUAL) { if (avn->getSize() + (int4)multop->getIn(1)->getOffset() == lvn->getSize()) {
Varnode *hibit = getHiBit(lvn->getDef()); // We have SUB( avn, #hi ) s< 0
if (hibit != (Varnode *)0) { // Test for (hi ^ lo) s<= -1 data.opSetInput(op,avn,0);
if (hibit->isConstant()) data.opSetInput(op,data.newConstant(avn->getSize(),0),1);
data.opSetInput(op,data.newConstant(hibit->getSize(),hibit->getOffset()),0); return 1;
else }
data.opSetInput(op,hibit,0); }
data.opSetOpcode(op,CPUI_INT_NOTEQUAL); else if (multop->code() == CPUI_INT_NEGATE) {
data.opSetInput(op,data.newConstant(hibit->getSize(),0),1); // We have ~avn s< 0
avn = multop->getIn(0);
if (avn->isFree()) return 0;
data.opSetInput(op,avn,1);
data.opSetInput(op,data.newConstant(avn->getSize(),calc_mask(avn->getSize())),0);
return 1; return 1;
} }
} }