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Allow overlaps in priority case statements (#2864)

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This will still warn if a case item is completely covered by previous
items, but will no longer complain about overlaps like this:

    priority casez (foo_i)
      2'b ?1: bar_o = 3'd0;
      2'b 1?: bar_o = 3'd1;

Before, there was a warning for the second statement because the first
two patterns match 2'b11.
This commit is contained in:
Rupert Swarbrick
2021-03-28 19:57:36 -04:00
committed by GitHub
parent 014bffdf5e
commit d6c2e2faf6
4 changed files with 113 additions and 11 deletions
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src/V3Case.cpp
+36 -11
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@@ -159,11 +159,13 @@ private:
return false; // Too wide for analysis
}
UINFO(8, "Simple case statement: " << nodep << endl);
uint32_t numCases = 1UL << m_caseWidth;
// Zero list of items for each value
for (uint32_t i = 0; i < (1UL << m_caseWidth); ++i) m_valueItem[i] = nullptr;
for (uint32_t i = 0; i < numCases; ++i) m_valueItem[i] = nullptr;
// Now pick up the values for each assignment
// We can cheat and use uint32_t's because we only support narrow case's
bool bitched = false;
bool reportedOverlap = false;
bool reportedSubcase = false;
for (AstCaseItem* itemp = nodep->itemsp(); itemp;
itemp = VN_CAST(itemp->nextp(), CaseItem)) {
for (AstNode* icondp = itemp->condsp(); icondp; icondp = icondp->nextp()) {
@@ -179,29 +181,52 @@ private:
V3Number numval(itemp, iconstp->width());
numval.opBitsOne(iconstp->num());
uint32_t val = numval.toUInt();
for (uint32_t i = 0; i < (1UL << m_caseWidth); ++i) {
uint32_t firstOverlap = 0;
bool foundOverlap = false;
bool foundHit = false;
for (uint32_t i = 0; i < numCases; ++i) {
if ((i & mask) == val) {
if (!m_valueItem[i]) {
m_valueItem[i] = itemp;
} else if (!itemp->ignoreOverlap() && !bitched) {
icondp->v3warn(CASEOVERLAP,
"Case values overlap (example pattern 0x"
<< std::hex << i << ")");
bitched = true;
foundHit = true;
} else if (!foundOverlap && !itemp->ignoreOverlap()) {
firstOverlap = i;
foundOverlap = true;
m_caseNoOverlapsAllCovered = false;
}
}
}
if (!nodep->priorityPragma()) {
// If this case statement doesn't have the priority
// keyword, we want to warn on any overlap.
if (!reportedOverlap && foundOverlap) {
icondp->v3warn(CASEOVERLAP, "Case values overlap (example pattern 0x"
<< std::hex << firstOverlap << ")");
reportedOverlap = true;
}
} else {
// If this is a priority case, we only want to complain
// if every possible value for this item is already hit
// by some other item. This is true if foundHit is
// false.
if (!reportedSubcase && !foundHit) {
icondp->v3warn(CASEOVERLAP,
"Case item ignored: every matching value is covered "
"by an earlier item");
reportedSubcase = true;
}
}
}
}
// Defaults were moved to last in the caseitem list by V3LinkDot
if (itemp->isDefault()) { // Case statement's default... Fill the table
for (uint32_t i = 0; i < (1UL << m_caseWidth); ++i) {
for (uint32_t i = 0; i < numCases; ++i) {
if (!m_valueItem[i]) m_valueItem[i] = itemp;
}
}
}
for (uint32_t i = 0; i < (1UL << m_caseWidth); ++i) {
for (uint32_t i = 0; i < numCases; ++i) {
if (!m_valueItem[i]) {
nodep->v3warn(CASEINCOMPLETE, "Case values incompletely covered "
"(example pattern 0x"
@@ -218,7 +243,7 @@ private:
// Convert valueItem from AstCaseItem* to the expression
// Not done earlier, as we may now have a nullptr because it's just a ";" NOP branch
for (uint32_t i = 0; i < (1UL << m_caseWidth); ++i) {
for (uint32_t i = 0; i < numCases; ++i) {
m_valueItem[i] = VN_CAST(m_valueItem[i], CaseItem)->bodysp();
}
return true; // All is fine