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Remove AstJumpLabel (#6221)

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Remove AstJumpLabel

AstJumpGo now references one if its enclosing AstJumpBlocks, and
branches straight after the referenced block.

That is:

```
JumpBlock a {
   ...
   JumpGo(a);
   ...
}
// <--- the JumpGo(a) goes here
```

This is sufficient for all use cases and makes control flow much easier to
reason about. As a result, V3Const can optimize a bit more aggressively.

Second half of, and fixes #6216
This commit is contained in:
Geza Lore
2025-07-23 17:51:16 +01:00
committed by GitHub
parent 763183f067
commit 7c5d462564
10 changed files with 164 additions and 236 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/V3LinkJump.cpp
+49 -55
View File
@@ -45,8 +45,8 @@ VL_DEFINE_DEBUG_FUNCTIONS;
class LinkJumpVisitor final : public VNVisitor {
// NODE STATE
// AstNode::user1() -> AstJumpLabel*, for this block if endOfIter
// AstNode::user2() -> AstJumpLabel*, for this block if !endOfIter
// AstNode::user1() -> AstJumpBlock*, for body of this loop
// AstNode::user2() -> AstJumpBlock*, for this block
// AstNodeBlock::user3() -> bool, true if contains a fork
const VNUser1InUse m_user1InUse;
const VNUser2InUse m_user2InUse;
@@ -65,36 +65,34 @@ class LinkJumpVisitor final : public VNVisitor {
"__VprocessQueue"}; // Names for queues needed for 'disable' handling
// METHODS
AstJumpLabel* findAddLabel(AstNode* nodep, bool endOfIter) {
// Put label under given node, and if WHILE optionally at end of iteration
UINFO(4, "Create label for " << nodep);
if (VN_IS(nodep, JumpLabel)) return VN_AS(nodep, JumpLabel); // Done
// Get (and create if necessary) the JumpBlock for this statement
AstJumpBlock* getJumpBlock(AstNode* nodep, bool endOfIter) {
// Wrap 'nodep' in JumpBlock. If loop, wrap the body instead if endOfIter is true
UINFO(4, "Create JumpBlock for " << nodep);
// Made it previously? We always jump to the end, so this works out
if (endOfIter) {
if (nodep->user1p()) return VN_AS(nodep->user1p(), JumpLabel);
if (nodep->user1p()) return VN_AS(nodep->user1p(), JumpBlock);
} else {
if (nodep->user2p()) return VN_AS(nodep->user2p(), JumpLabel);
if (nodep->user2p()) return VN_AS(nodep->user2p(), JumpBlock);
}
AstNode* underp = nullptr;
bool under_and_next = true;
if (VN_IS(nodep, NodeBlock)) {
underp = VN_AS(nodep, NodeBlock)->stmtsp();
} else if (VN_IS(nodep, NodeFTask)) {
underp = VN_AS(nodep, NodeFTask)->stmtsp();
} else if (VN_IS(nodep, Foreach)) {
if (AstNodeBlock* const blockp = VN_CAST(nodep, NodeBlock)) {
underp = blockp->stmtsp();
} else if (AstNodeFTask* const fTaskp = VN_CAST(nodep, NodeFTask)) {
underp = fTaskp->stmtsp();
} else if (AstForeach* const foreachp = VN_CAST(nodep, Foreach)) {
if (endOfIter) {
underp = VN_AS(nodep, Foreach)->stmtsp();
underp = foreachp->stmtsp();
} else {
underp = nodep;
under_and_next = false; // IE we skip the entire foreach
}
} else if (VN_IS(nodep, While)) {
} else if (AstWhile* const whilep = VN_CAST(nodep, While)) {
if (endOfIter) {
// Note we jump to end of bodysp; a FOR loop has its
// increment under incsp() which we don't skip
underp = VN_AS(nodep, While)->stmtsp();
underp = whilep->stmtsp();
} else {
underp = nodep;
under_and_next = false; // IE we skip the entire while
@@ -118,36 +116,32 @@ class LinkJumpVisitor final : public VNVisitor {
UASSERT_OBJ(underp, nodep, "Break/disable/continue not under expected statement");
UINFO(5, " Underpoint is " << underp);
if (VN_IS(underp, JumpLabel)) {
return VN_AS(underp, JumpLabel);
} else { // Move underp stuff to be under a new label
AstJumpBlock* const blockp = new AstJumpBlock{nodep->fileline(), nullptr};
AstJumpLabel* const labelp = new AstJumpLabel{nodep->fileline(), blockp};
blockp->labelp(labelp);
VNRelinker repHandle;
if (under_and_next) {
underp->unlinkFrBackWithNext(&repHandle);
} else {
underp->unlinkFrBack(&repHandle);
}
repHandle.relink(blockp);
blockp->addStmtsp(underp);
// Keep any AstVars under the function not under the new JumpLabel
for (AstNode *nextp, *varp = underp; varp; varp = nextp) {
nextp = varp->nextp();
if (VN_IS(varp, Var)) blockp->addHereThisAsNext(varp->unlinkFrBack());
}
// Label goes last
blockp->addEndStmtsp(labelp);
if (endOfIter) {
nodep->user1p(labelp);
} else {
nodep->user2p(labelp);
}
return labelp;
// If already wrapped, we are done ...
if (!underp->nextp() || !under_and_next) {
if (AstJumpBlock* const blockp = VN_CAST(underp, JumpBlock)) return blockp;
}
// Move underp stuff to be under a new AstJumpBlock
VNRelinker repHandle;
if (under_and_next) {
underp->unlinkFrBackWithNext(&repHandle);
} else {
underp->unlinkFrBack(&repHandle);
}
AstJumpBlock* const blockp = new AstJumpBlock{nodep->fileline(), underp};
if (endOfIter) {
nodep->user1p(blockp);
} else {
nodep->user2p(blockp);
}
repHandle.relink(blockp);
// Keep any AstVars under the function not under the new JumpLabel
for (AstNode *nextp, *varp = underp; varp; varp = nextp) {
nextp = varp->nextp();
if (VN_IS(varp, Var)) blockp->addHereThisAsNext(varp->unlinkFrBack());
}
return blockp;
}
void addPrefixToBlocksRecurse(const std::string& prefix, AstNode* const nodep) {
// Add a prefix to blocks
@@ -379,8 +373,8 @@ class LinkJumpVisitor final : public VNVisitor {
nodep->lhsp()->unlinkFrBackWithNext()});
}
// Jump to the end of the function call
AstJumpLabel* const labelp = findAddLabel(m_ftaskp, false);
nodep->addHereThisAsNext(new AstJumpGo{nodep->fileline(), labelp});
AstJumpBlock* const blockp = getJumpBlock(m_ftaskp, false);
nodep->addHereThisAsNext(new AstJumpGo{nodep->fileline(), blockp});
}
nodep->unlinkFrBack();
VL_DO_DANGLING(pushDeletep(nodep), nodep);
@@ -391,8 +385,8 @@ class LinkJumpVisitor final : public VNVisitor {
nodep->v3error("break isn't underneath a loop");
} else {
// Jump to the end of the loop
AstJumpLabel* const labelp = findAddLabel(m_loopp, false);
nodep->addNextHere(new AstJumpGo{nodep->fileline(), labelp});
AstJumpBlock* const blockp = getJumpBlock(m_loopp, false);
nodep->addNextHere(new AstJumpGo{nodep->fileline(), blockp});
}
nodep->unlinkFrBack();
VL_DO_DANGLING(pushDeletep(nodep), nodep);
@@ -404,8 +398,8 @@ class LinkJumpVisitor final : public VNVisitor {
} else {
// Jump to the end of this iteration
// If a "for" loop then need to still do the post-loop increment
AstJumpLabel* const labelp = findAddLabel(m_loopp, true);
nodep->addNextHere(new AstJumpGo{nodep->fileline(), labelp});
AstJumpBlock* const blockp = getJumpBlock(m_loopp, true);
nodep->addNextHere(new AstJumpGo{nodep->fileline(), blockp});
}
nodep->unlinkFrBack();
VL_DO_DANGLING(pushDeletep(nodep), nodep);
@@ -444,8 +438,8 @@ class LinkJumpVisitor final : public VNVisitor {
"Unsupported: disabling block that contains a fork");
} else {
// Jump to the end of the named block
AstJumpLabel* const labelp = findAddLabel(beginp, false);
nodep->addNextHere(new AstJumpGo{nodep->fileline(), labelp});
AstJumpBlock* const blockp = getJumpBlock(beginp, false);
nodep->addNextHere(new AstJumpGo{nodep->fileline(), blockp});
}
} else {
nodep->v3warn(E_UNSUPPORTED, "disable isn't underneath a begin with name: '"