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Fix compiler warning when WIDTH warning ignored on large compare.

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This commit is contained in:
Wilson Snyder
2017-10-01 10:21:27 -04:00
parent c7cbe11ba4
commit 04ca6a4307
4 changed files with 193 additions and 9 deletions
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src/V3Const.cpp
+28 -9
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@@ -369,11 +369,11 @@ private:
return true;
}
bool operandBiExtendConst(AstNodeBiop* nodep) {
bool operandBiExtendConstShrink(AstNodeBiop* nodep) {
// 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
// The constant must have zero bits (+ 1 if signed) or compare
// would be incorrect. See also operandBiExtendConst
AstExtend* extendp = nodep->rhsp()->castExtend();
if (!extendp) return false;
AstNode* smallerp = extendp->lhsp();
@@ -395,6 +395,19 @@ private:
if (debug()>=9) nodep->dumpTree(cout,"BI(EXTEND)-ou:");
return true;
}
bool operandBiExtendConstOver(AstNodeBiop* nodep) {
// EQ(const{width32}, EXTEND(xx{width3})) -> constant
// When the constant has non-zero bits above the extend it's a constant.
// Avoids compiler warning
AstExtend* extendp = nodep->rhsp()->castExtend();
if (!extendp) return false;
AstNode* smallerp = extendp->lhsp();
int subsize = smallerp->width();
AstConst* constp = nodep->lhsp()->castConst();
if (!constp) return false;
if (constp->num().isBitsZero(constp->width()-1, subsize)) return false;
return true;
}
AstNode* afterComment(AstNode* nodep) {
// Ignore comments, such as to determine if a AstIf is empty.
@@ -2216,12 +2229,18 @@ private:
TREEOP ("AstShiftR{operandShiftShift(nodep)}", "replaceShiftShift(nodep)");
TREEOP ("AstWordSel{operandWordOOB(nodep)}", "replaceZero(nodep)");
// Compress out EXTENDs to appease loop unroller
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");
TREEOPV("AstEq {$rhsp.castExtend,operandBiExtendConstShrink(nodep)}", "DONE");
TREEOPV("AstNeq {$rhsp.castExtend,operandBiExtendConstShrink(nodep)}", "DONE");
TREEOPV("AstGt {$rhsp.castExtend,operandBiExtendConstShrink(nodep)}", "DONE");
TREEOPV("AstGte {$rhsp.castExtend,operandBiExtendConstShrink(nodep)}", "DONE");
TREEOPV("AstLt {$rhsp.castExtend,operandBiExtendConstShrink(nodep)}", "DONE");
TREEOPV("AstLte {$rhsp.castExtend,operandBiExtendConstShrink(nodep)}", "DONE");
TREEOPV("AstEq {$rhsp.castExtend,operandBiExtendConstOver(nodep)}", "replaceZero(nodep)");
TREEOPV("AstNeq {$rhsp.castExtend,operandBiExtendConstOver(nodep)}", "replaceNum(nodep,1)");
TREEOPV("AstGt {$rhsp.castExtend,operandBiExtendConstOver(nodep)}", "replaceNum(nodep,1)");
TREEOPV("AstGte {$rhsp.castExtend,operandBiExtendConstOver(nodep)}", "replaceNum(nodep,1)");
TREEOPV("AstLt {$rhsp.castExtend,operandBiExtendConstOver(nodep)}", "replaceZero(nodep)");
TREEOPV("AstLte {$rhsp.castExtend,operandBiExtendConstOver(nodep)}", "replaceZero(nodep)");
// Identical operands on both sides
// AstLogAnd/AstLogOr already converted to AstAnd/AstOr for these rules
// AstAdd->ShiftL(#,1) but uncommon