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authorjsmall-nvidia <jsmall@nvidia.com>2019-05-31 17:20:37 -0400
committerGitHub <noreply@github.com>2019-05-31 17:20:37 -0400
commit6cbc3929a54d37bd23cb5efa8e3320ba02f78b2f (patch)
tree5a23cb47782e9e2a77762c90dd35da1005eba8d0 /source/slang/ir-restructure.cpp
parentb81ff3ef968d1cc4e954b31a1812b3c391d17b02 (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.cpp663
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;
- }
-}