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Optimizer: Put constants on left side of compares to match other AstBiOps and extend optimizations. No runtime result change intended.

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This commit is contained in:
Wilson Snyder
2014-03-09 17:13:37 -04:00
parent 45bbae80e7
commit dce4519995
4 changed files with 40 additions and 31 deletions
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src/V3Const.cpp
+20 -12
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@@ -327,27 +327,27 @@ private:
}
bool operandBiExtendConst(AstNodeBiop* nodep) {
// Loop unrolling likes standalone compares
// EQ(EXTEND(xx{width3}), const{width32}) -> EQ(xx{3},const{3})
// Loop unrolling favors standalone compares
// EQ(const{width32}, EXTEND(xx{width3})) -> EQ(const{3}, xx{3})
// Beware that the constant must have zero bits (+ 1 if signed) or compare
// would be incorrect
AstExtend* extendp = nodep->lhsp()->castExtend();
AstExtend* extendp = nodep->rhsp()->castExtend();
if (!extendp) return false;
AstNode* smallerp = extendp->lhsp();
int subsize = smallerp->width();
AstConst* constp = nodep->rhsp()->castConst();
AstConst* constp = nodep->lhsp()->castConst();
if (!constp) return false;
if (!constp->num().isBitsZero(constp->width()-1, subsize)) return false;
//
if (debug()>=9) nodep->dumpTree(cout,"BI(EXTEND)-in:");
smallerp->unlinkFrBack();
extendp->unlinkFrBack()->deleteTree(); // aka nodep->lhsp.
nodep->lhsp(smallerp);
nodep->rhsp(smallerp);
constp->unlinkFrBack();
V3Number num (constp->fileline(), subsize);
num.opAssign(constp->num());
nodep->rhsp(new AstConst(constp->fileline(), num));
nodep->lhsp(new AstConst(constp->fileline(), num));
constp->deleteTree(); constp=NULL;
if (debug()>=9) nodep->dumpTree(cout,"BI(EXTEND)-ou:");
return true;
@@ -1812,6 +1812,14 @@ private:
TREEOP ("AstNodeBiComAsv{operandAsvSame(nodep)}", "replaceAsv(nodep)");
TREEOP ("AstNodeBiComAsv{operandAsvLUp(nodep)}", "replaceAsvLUp(nodep)");
TREEOP ("AstNodeBiComAsv{operandAsvRUp(nodep)}", "replaceAsvRUp(nodep)");
TREEOP ("AstLt {!$lhsp.castConst,$rhsp.castConst}", "AstGt {$rhsp,$lhsp}");
TREEOP ("AstLtS {!$lhsp.castConst,$rhsp.castConst}", "AstGtS {$rhsp,$lhsp}");
TREEOP ("AstLte {!$lhsp.castConst,$rhsp.castConst}", "AstGte {$rhsp,$lhsp}");
TREEOP ("AstLteS {!$lhsp.castConst,$rhsp.castConst}", "AstGteS{$rhsp,$lhsp}");
TREEOP ("AstGt {!$lhsp.castConst,$rhsp.castConst}", "AstLt {$rhsp,$lhsp}");
TREEOP ("AstGtS {!$lhsp.castConst,$rhsp.castConst}", "AstLtS {$rhsp,$lhsp}");
TREEOP ("AstGte {!$lhsp.castConst,$rhsp.castConst}", "AstLte {$rhsp,$lhsp}");
TREEOP ("AstGteS {!$lhsp.castConst,$rhsp.castConst}", "AstLteS{$rhsp,$lhsp}");
// v--- *1* as These ops are always first, as we warn before replacing
TREEOP1("AstLt {$lhsp, $rhsp.isZero}", "replaceNumSigned(nodep,0)");
TREEOP1("AstGte {$lhsp, $rhsp.isZero}", "replaceNumSigned(nodep,1)");
@@ -1861,12 +1869,12 @@ private:
TREEOP ("AstShiftR{operandShiftShift(nodep)}", "replaceShiftShift(nodep)");
TREEOP ("AstWordSel{operandWordOOB(nodep)}", "replaceZero(nodep)");
// Compress out EXTENDs to appease loop unroller
TREEOPV("AstEq {$lhsp.castExtend,operandBiExtendConst(nodep)}", "DONE");
TREEOPV("AstNeq {$lhsp.castExtend,operandBiExtendConst(nodep)}", "DONE");
TREEOPV("AstGt {$lhsp.castExtend,operandBiExtendConst(nodep)}", "DONE");
TREEOPV("AstGte {$lhsp.castExtend,operandBiExtendConst(nodep)}", "DONE");
TREEOPV("AstLt {$lhsp.castExtend,operandBiExtendConst(nodep)}", "DONE");
TREEOPV("AstLte {$lhsp.castExtend,operandBiExtendConst(nodep)}", "DONE");
TREEOPV("AstEq {$rhsp.castExtend,operandBiExtendConst(nodep)}", "DONE");
TREEOPV("AstNeq {$rhsp.castExtend,operandBiExtendConst(nodep)}", "DONE");
TREEOPV("AstGt {$rhsp.castExtend,operandBiExtendConst(nodep)}", "DONE");
TREEOPV("AstGte {$rhsp.castExtend,operandBiExtendConst(nodep)}", "DONE");
TREEOPV("AstLt {$rhsp.castExtend,operandBiExtendConst(nodep)}", "DONE");
TREEOPV("AstLte {$rhsp.castExtend,operandBiExtendConst(nodep)}", "DONE");
// Identical operands on both sides
// AstLogAnd/AstLogOr already converted to AstAnd/AstOr for these rules
// AstAdd->ShiftL(#,1) but uncommon