diff options
| author | jsmall-nvidia <jsmall@nvidia.com> | 2019-05-31 17:20:37 -0400 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2019-05-31 17:20:37 -0400 |
| commit | 6cbc3929a54d37bd23cb5efa8e3320ba02f78b2f (patch) | |
| tree | 5a23cb47782e9e2a77762c90dd35da1005eba8d0 /source/slang/ir-restructure.cpp | |
| parent | b81ff3ef968d1cc4e954b31a1812b3c391d17b02 (diff) | |
Use slang- prefix on slang compiler and core source (#973)
* Prefixing source files in source/slang with slang-
* Prefix source in source/slang with slang- prefix.
* Rename core source files with slang- prefix.
* Update project files.
* Fix problems from automatic merge.
Diffstat (limited to 'source/slang/ir-restructure.cpp')
| -rw-r--r-- | source/slang/ir-restructure.cpp | 663 |
1 files changed, 0 insertions, 663 deletions
diff --git a/source/slang/ir-restructure.cpp b/source/slang/ir-restructure.cpp deleted file mode 100644 index 47a0d1fee..000000000 --- a/source/slang/ir-restructure.cpp +++ /dev/null @@ -1,663 +0,0 @@ -// ir-restructure.cpp -#include "ir-restructure.h" - -#include "ir.h" -#include "ir-insts.h" - -namespace Slang -{ - bool Region::isDescendentOf(Region* other) - { - Region* rr = this; - while( rr ) - { - if(rr == other) - return true; - - rr = rr->getParent(); - } - return false; - } - - bool Region::isDescendentOf(IRBlock* block) - { - Region* rr = this; - while( rr ) - { - if( rr->getFlavor() == Region::Flavor::Simple ) - { - SimpleRegion* simpleRegion = (SimpleRegion*) rr; - if(simpleRegion->block == block) - return true; - } - - rr = rr->getParent(); - } - return false; - } - - /// An "active" label during control flow (re)structuring. - struct LabelStack - { - /// Possible operations associated with labels. - enum class Op - { - Break, - Continue, - - CountOf, - }; - - /// What kind of operation does a branch to this label represent? - Op op; - - /// The next label down on the stack - LabelStack* parent; - - /// The block the represents this label in the IR control flow graph. - IRBlock* block; - - /// The region that represents this label in the structured program - Region* region; - }; - - /// State used when restructuring control flow. - struct ControlFlowRestructuringContext - { - /// Sink to use when diagnosing errors in control-flow restructuring. - /// - /// The restructuring pass should be able to handle anything the front-end - /// throws at it, so these errors will all be unexpected. Still, we need - /// a way to report them cleanly without crashing the process. - /// - DiagnosticSink* sink = nullptr; - DiagnosticSink* getSink() { return sink; } - - /// The region tree we are in the process of building. - RegionTree* regionTree = nullptr; - }; - - /// Convert a range of blocks in the IR CFG into a region. - /// - /// We want to generate a region that stands in for the - /// blocks that are logically in the internal [begin, end) - /// which we consider as representing a single-entry multiple-exit - /// sub-graph. Note that `end` is *not* part of the sub-graph, - /// but instead points to a block that is logically "after" - /// the sub-graph. `end` can be `null` to indicate that the - /// sub-graph extends as far as possible. - /// - /// Because there can be multiple exits, control flow may - /// exit the sub-graph without branching to `end`, any - /// such "non-local" branching should be to one of the - /// blocks stored in the current `LabelStack`. - /// - // TODO: Eventually we should replace all of this logic with - // a variation on the "Relooper" algorithm as it is used - // in Emscripten. - // - static RefPtr<Region> generateRegionsForIRBlocks( - ControlFlowRestructuringContext* ctx, - Region* inParentRegion, - IRBlock* begin, - IRBlock* end, - LabelStack* initialLabels, // Labels to use at the start - LabelStack* labels = nullptr) // Labels to switch to after emitting first basic block - { - if(!labels) - labels = initialLabels; - auto useLabels = initialLabels; - - // - // We will try to build up as long of a sequential/simple region - // as possible, to avoid deep recursion in this algorithm. - // - RefPtr<Region> resultRegion = nullptr; - RefPtr<Region>* resultLink = &resultRegion; - - // As we move along, the parent region to use for regions - // we create will shift, so we need a temporary to track - // the current parent region. - // - Region* parentRegion = inParentRegion; - - // - // We will start with the `begin` block, and try to proceed - // sequentially until we see the `end` block, or run into - // an edge that exits teh region. - // - IRBlock* block = begin; - while(block != end) - { - // If the block we are trying to emit has been registered as a - // destination label (e.g. for a loop or `switch`) then we - // need to exit the current region, which amounts to generating - // a `break` or `continue` operation. - // - // TODO: we eventually need to handle the possibility of - // multi-level break/continue targets, which could be challenging. - - // Because we will only support single-level break/continue, we - // want to resolve what is the most recent label that is "active" - // for the given operation (`break` or `continue`). - // - // We will do this with a naive loop, just to keep things simple. - // We start with no block "regsitered" as the target for each - // operation. - // - IRBlock* registeredBlock[(int)LabelStack::Op::CountOf] = {}; - for( auto ll = useLabels; ll; ll = ll->parent ) - { - // For each active label, see if it is the first one - // we encounter for the given op. - // - if(!registeredBlock[(int)ll->op]) - { - registeredBlock[(int)ll->op] = ll->block; - } - } - - // Next we will search through *all* of the registered labels, - // and see if one of them matches the current `block`. - // - for(auto ll = useLabels; ll; ll = ll->parent) - { - // Does this label match the block we are trying to translate? - if(ll->block != block) - continue; - - // Okay, the block we are trying to generate code for is a label - // that we should branch to (we shouldn't just emit the code here - // and now...) - // - // We should first confirm that the block is the inner-most label - // registered for the given control-flow op (`break` or `continue`) - // because if it *isn't* we currently can't generate code. - // - if(block != registeredBlock[(int)ll->op]) - { - ctx->getSink()->diagnose(block, Diagnostics::multiLevelBreakUnsupported); - } - - // Now we need to create a structured `break` or `continue` operation - // to match the operation associated with the target. - // - switch(ll->op) - { - case LabelStack::Op::Break: - { - auto outerRegion = (BreakableRegion*) ll->region; - RefPtr<BreakRegion> breakRegion = new BreakRegion(parentRegion, outerRegion); - - *resultLink = breakRegion; - resultLink = nullptr; - } - break; - - case LabelStack::Op::Continue: - { - auto outerRegion = (LoopRegion*) ll->region; - RefPtr<ContinueRegion> continueRegion = new ContinueRegion(parentRegion, outerRegion); - - *resultLink = continueRegion; - resultLink = nullptr; - } - break; - } - - // If the `block` matched an active label, then we should have - // created a branch, and there is nothing to be done here. - return resultRegion; - } - - // We now know that the given `block` is part of our control-flow region, - // so we need to output a simple region that executes the code in that block. - // - RefPtr<SimpleRegion> simpleRegion = new SimpleRegion(parentRegion, block); - - // We need to register the mapping from `block` to this region, but in - // general this isn't a one-to-one mapping, but rather one-to-many. - // This is because a "continue clause" in a `for` loop might get duplicated - // at each `continue` site in the output code. To deal with this - // we build a singly-linked list of regions for each block. - // - // TODO: confirm that continue clauses are the only case that leads - // to duplication. - // - // TODO: remove this workaround once we have a more powerful restructuring - // pass that avoids duplicating blocks (by introducing new temporaries...) - // - SimpleRegion* nextSimpleRegionForSameBlock = nullptr; - ctx->regionTree->mapBlockToRegion.TryGetValue(block, nextSimpleRegionForSameBlock); - ctx->regionTree->mapBlockToRegion[block] = simpleRegion; - - *resultLink = simpleRegion; - resultLink = &simpleRegion->nextRegion; - parentRegion = simpleRegion; - - // The simple region we created will represent all of the non-terminator - // instructions in the `block`, so now we need to figure out what to - // create to represent that terminator. - // - auto terminator = block->getTerminator(); - SLANG_ASSERT(terminator != nullptr); - switch (terminator->op) - { - default: - case kIROp_conditionalBranch: - // Note: we don't currently generate ordinary `conditionalBranch` instructions, - // and instead only generate `ifElse` instructions, which include additional - // information that can inform our control-flow restructuring pass. - // - SLANG_UNEXPECTED("unhandled terminator instruction opcode"); - ; // fall through to: - case kIROp_Unreachable: - case kIROp_MissingReturn: - case kIROp_ReturnVal: - case kIROp_ReturnVoid: - case kIROp_discard: - // These cases are all simple terminators that can be handled as-is - // without needing to construct a separate `Region` to encapsulate them. - // - // We will cap off the current sequence of simple regions and return. - // - *resultLink = nullptr; - return resultRegion; - - case kIROp_ifElse: - { - // Here we have a two-way branch, so that we will construct a - // region representing an `if` statement. - // - auto ifInst = (IRIfElse*)terminator; - auto condition = ifInst->getCondition(); - auto trueBlock = ifInst->getTrueBlock(); - auto falseBlock = ifInst->getFalseBlock(); - auto afterBlock = ifInst->getAfterBlock(); - - - RefPtr<IfRegion> ifRegion = new IfRegion(parentRegion, condition); - - // The region for the "then" part of things will consist of - // the range of blocks `[trueBlock, afterBlock)`. - // - // This logic assumes that `afterBlock` is a valid structured - // "join point" such that any branch out of the sub-region - // either leads to `afterBlock` *or* one of the labels - // that is already present on our label stack. - // - ifRegion->thenRegion = generateRegionsForIRBlocks( - ctx, - ifRegion, - trueBlock, - afterBlock, - labels); - - // Generating a region for the `else` part is similar. - // Note that it is possible for this to be a `null` - // region, if `falseBlock == afterBlock`. - // - ifRegion->elseRegion = generateRegionsForIRBlocks( - ctx, - ifRegion, - falseBlock, - afterBlock, - labels); - - *resultLink = ifRegion; - resultLink = &ifRegion->nextRegion; - parentRegion = ifRegion; - - // Continue with the block after the `ifElse` instruction. - block = afterBlock; - } - break; - - case kIROp_loop: - { - // The terminator in this case is the header for a structured loop. - // - auto loopInst = (IRLoop*) terminator; - auto bodyBlock = loopInst->getTargetBlock(); - auto afterBlock = loopInst->getBreakBlock(); - - RefPtr<LoopRegion> loopRegion = new LoopRegion(parentRegion, loopInst); - - // We will need to set up entries on our label stack to - // represent the targets for `break` or `continue` - // operations inside the loop. - // - // First we set up the stack entry for the `break` label, - // which will refer to the block *after* the loop. - // - // The region we specify for the label will still be - // the loop region, though, because the loop is what - // we are breaking out of. - // - LabelStack loopBreakLabelStack; - loopBreakLabelStack.parent = labels; - loopBreakLabelStack.block = afterBlock; - loopBreakLabelStack.region = loopRegion; - loopBreakLabelStack.op = LabelStack::Op::Break; - - // - // The `continue` label warrants a bit more careful explanation, - // because it will *not* refer to the block that was regsitered - // as the continue target in the IR `loop` instruction. This - // is because we will always emit our loops as `for(;;) { ... }` - // with no continue clause at all, so that a `continue` in - // the output code will always refer to the top of the loop. - // - // This means that the `continue` label for the purposes of - // structured control flow will be the start of the loop body: - // - LabelStack loopContinueLabelStack; - loopContinueLabelStack.parent = &loopBreakLabelStack; - loopContinueLabelStack.block = bodyBlock; - loopContinueLabelStack.region = loopRegion; - loopContinueLabelStack.op = LabelStack::Op::Continue; - // - // Note: by ignoring the original continue block from the - // high-level loop, we create a situation where that code - // might get emitted more than once (once per implicit - // or explicit `continue` site in the original program). - // - // That is an acceptable trade-off for now, because continue - // blocks will usually be small (and fxc makes the same choice), - // but it could lead to Bad Things if somebody were to call - // a function in their continue clause, and that function does - // a compute shader barrier operation. - // - // A better long-term fix is to take a high-level loop like: - // - // for(A; B; C) { ... continue; ... break; ... } - // - // and translate it into something like the following (assuming - // we have labeled statements and multi-level `break`): - // - // A; - // Outer: for(;;) { - // Inner: for(;;) { - // if(B) {} else break Outer; - // ... - // break Inner; // `continue` becomes break of inner loop - // ... - // break Outer; // `break` becomes break of outer loop - // ... - // break; // inner loop unconditionally breaks at the end - // } - // C; // continue clause comes after inner loop - // } - // - // If you draw up a control flow graph for that code, you'll find - // it is equivalent to the orignal `for` loop, but now supports - // arbitrary code (not just a single expression) for the continue clause. - // Unlike the current code-duplication solution, `C` appears only once - // in the output, and seems to clearly be at a "joint point" for control - // flow so that it is clear that a barrier there is valid in GLSL. - // - // Anyway, back our regularly scheduled programming. - // - // With the label stack stuff set up, we want to take the region - // of the CFG defined by `[bodyBlock, afterBlock)` and turn it into - // the body region for our loop. - // - // The only thing we want to be a little bit careful about is - // that we don't want the logic at the top of this function - // that looks for a block it can translate into a `continue` - // to trigger on `bodyBlock`, since that means we'd just turn - // the whole body into a single `continue`. - // - // To avoid this problem, we pass in two different label stacks: - // one to use for the first block, and one to use for subsequent - // blocks. - // - loopRegion->body = generateRegionsForIRBlocks( - ctx, - loopRegion, - bodyBlock, - // TODO: should we pass `afterBlock` here instead of `null`? - nullptr, - // For the first block, we only want the `break` label active - &loopBreakLabelStack, - // After the first block, we can safely use the `continue` label too - &loopContinueLabelStack); - - *resultLink = loopRegion; - resultLink = &loopRegion->nextRegion; - parentRegion = loopRegion; - - // Continue with the block after the loop - block = afterBlock; - } - break; - - case kIROp_unconditionalBranch: - { - // Here we have an unconditional branch that was - // not covered by one of our labels for non-local - // branches (`break` or `continue`). - // - // We will thus assume that the target of the - // branch is part of the same region we are building, - // and continue with the target block; - // - auto branchInst = (IRUnconditionalBranch*) terminator; - block = branchInst->getTargetBlock(); - } - break; - - case kIROp_Switch: - { - // A `switch` instruction will always translate - // to a `SwitchRegion` and then to a `switch` statement. - // - // We will need to take care to emit `case`s in ways - // that avoid code duplication. - // - // The logic here isn't going to be robust in edge cases - // (please don't write Duff's Device in Slang just yet). - // Doing significantly better than what is here would - // require something like the Relooper algorithm, though. - // - auto switchInst = (IRSwitch*) terminator; - auto condition = switchInst->getCondition(); - auto breakLabel = switchInst->getBreakLabel(); - auto defaultLabel = switchInst->getDefaultLabel(); - - RefPtr<SwitchRegion> switchRegion = new SwitchRegion(parentRegion, condition); - - // A direct branch to the block after the `switch` can - // be emitted as a `break` statement, so we will register - // the appropriate label on a label stack: - // - LabelStack switchBreakLabelStack; - switchBreakLabelStack.parent = labels; - switchBreakLabelStack.op = LabelStack::Op::Break; - switchBreakLabelStack.block = breakLabel; - switchBreakLabelStack.region = switchRegion; - - // We need to track whether we've dealt with - // the `default` case already. - // - bool defaultLabelHandled = false; - - // If the `default` case just branches to - // the join point, then we don't need to - // do anything with it. - // - if(defaultLabel == breakLabel) - defaultLabelHandled = true; - - // We will now iterate over the different `case`s, and - // try to group them together to minimize the number of - // sub-regions we have to create. - // - UInt caseIndex = 0; - UInt caseCount = switchInst->getCaseCount(); - while(caseIndex < caseCount) - { - // We are going to extract one case here, - // but we might need to fold additional - // cases into it, if they share the - // same label. - // - // Note: this makes assumptions that the - // IR code generator orders cases such - // that: (1) cases with the same label - // are consecutive, and (2) any case - // that "falls through" to another must - // come right before it in the list. - - auto caseVal = switchInst->getCaseValue(caseIndex); - auto caseLabel = switchInst->getCaseLabel(caseIndex); - caseIndex++; - - RefPtr<SwitchRegion::Case> currentCase = new SwitchRegion::Case(); - switchRegion->cases.add(currentCase); - - // Add the case value for this case, and any - // others that share the same label - // - for(;;) - { - currentCase->values.add(caseVal); - - // Are there any more `case`s left? - // - if(caseIndex >= caseCount) - break; - - // Does the next `case` share the same target label? - auto nextCaseLabel = switchInst->getCaseLabel(caseIndex); - if(nextCaseLabel != caseLabel) - break; - - // If those checks passed, then we will fold - // the next `case` into the same region, and - // keep looking. - caseVal = switchInst->getCaseValue(caseIndex); - caseIndex++; - } - - // The label for the current `case` might also - // be the label used by the `default` case, so - // check for that here. - // - if(caseLabel == defaultLabel) - { - switchRegion->defaultCase = currentCase; - defaultLabelHandled = true; - } - - // Now we need to generate a region for the instructions - // that make up this case. The 99% case will be that it - // will terminate with a `break` (or a `return`, - // `continue`, etc.) and so we can pass in `nullptr` - // for the ending block. - // - IRBlock* caseEndLabel = nullptr; - - // However, there is also the possibility that - // this `case` will fall through to the next, and - // so we need to prepare for that possibility here. - // - // If there *is* a next `case`, then we will set its - // label up as the "end" label when emitting - // the statements inside the block. - if(caseIndex < caseCount) - { - caseEndLabel = switchInst->getCaseLabel(caseIndex); - } - - // Now we can actually generate the region. - // - currentCase->body = generateRegionsForIRBlocks( - ctx, - switchRegion, - caseLabel, - caseEndLabel, - &switchBreakLabelStack); - } - - // If we've gone through all the cases and haven't - // managed to encounter the `default:` label, - // then assume it is a distinct case and handle it here. - if(!defaultLabelHandled) - { - RefPtr<SwitchRegion::Case> defaultCase = new SwitchRegion::Case(); - switchRegion->cases.add(defaultCase); - - // Note: we use `null` instead of `breakLabel` as the end block - // here, to ensure that the `default` region will end with an - // explicit `break` rather than just falling off the end. - - defaultCase->body = generateRegionsForIRBlocks( - ctx, - switchRegion, - defaultLabel, - nullptr, - &switchBreakLabelStack); - - switchRegion->defaultCase = defaultCase; - } - - *resultLink = switchRegion; - resultLink = &switchRegion->nextRegion; - parentRegion = switchRegion; - - // Continue with the block after the `switch` - block = breakLabel; - } - break; - } - - // After we've emitted the first block, we are safe from accidental - // cases where we'd emit an entire loop body as a single `continue`, - // so we can safely switch in whatever labels are intended to be used. - useLabels = labels; - - // If we reach this point, then we've emitted - // one block, and we have a new block where - // control flow continues. - // - // We need to handle a special case here, - // when control flow jumps back to the - // starting block of the range we were - // asked to work with: - if (block == begin) - { - break; - } - } - - // We seem to have reached the rend of the region - // without anything special happening. This means - // we should cap off the current sequence of regions - // and return what we have. - // - *resultLink = nullptr; - return resultRegion; - } - - RefPtr<RegionTree> generateRegionTreeForFunc( - IRGlobalValueWithCode* code, - DiagnosticSink* sink) - { - RefPtr<RegionTree> regionTree = new RegionTree(); - regionTree->irCode = code; - - ControlFlowRestructuringContext restructuringContext; - restructuringContext.sink = sink; - restructuringContext.regionTree = regionTree; - - regionTree->rootRegion = generateRegionsForIRBlocks( - &restructuringContext, - nullptr, - code->getFirstBlock(), - nullptr, - nullptr); - - return regionTree; - } -} |
