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Dave Bartolomeo
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C++: Share TInstruction across IR stages
Each stage of the IR reuses the majority of the instructions from previous stages. Previously, we've been wrapping each reused old instruction in a branch of the `TInstruction` type for the next stage. This causes use to create roughly three times as many `TInstruction` objects as we actually need. Now that IPA union types are supported in the compiler, we can share a single `TInstruction` IPA type across stages. We create a single `TInstruction` IPA type, with individual branches of this type for instructions created directly from the AST (`TRawInstruction`) and for instructions added by each stage of SSA construction (`T*PhiInstruction`, `T*ChiInstruction`, `T*UnreachedInstruction`). Each stage then defines a `TStageInstruction` type that is a union of all of the branches that can appear in that particular stage. The public `Instruction` class for each phase extends the `TStageInstruction` type for that stage. The interface that each stage exposes to the pyrameterized modules in the IR is now split into three pieces: - The `Raw` module, exposed only by the original IR construction stage. This module identifies which functions have IR, which `TRawInstruction`s exist, and which `IRVariable`s exist. - The `SSA` module, exposed only by the two SSA construction stages. This identifiers which `Phi`, `Chi`, and `Unreached` instructions exist. - The global module, exposed by all three stages. This module has all of the predicates whose implementation is different for each stage, like gathering definitions of `MemoryOperand`s. Similarly, there is now a single `TIRFunction` IPA type that is shared across all three stages. There is a single `IRFunctionBase` class that exposes the stage-indepdendent predicates; the `IRFunction` class for each stage extends `IRFunctionBase`. Most of the other changes are largely mechanical.
1 parent 7265e94 commit 1e863ac

28 files changed

Lines changed: 627 additions & 463 deletions

‎config/identical-files.json‎

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@@ -177,6 +177,11 @@
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"cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/internal/IRBlockImports.qll",
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"cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/IRBlockImports.qll"
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],
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"C++ IR IRFunctionImports": [
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"cpp/ql/src/semmle/code/cpp/ir/implementation/raw/internal/IRFunctionImports.qll",
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"cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/internal/IRFunctionImports.qll",
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"cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/IRFunctionImports.qll"
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],
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"C++ IR IRVariableImports": [
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"cpp/ql/src/semmle/code/cpp/ir/implementation/raw/internal/IRVariableImports.qll",
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"cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/internal/IRVariableImports.qll",

‎cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/IRFunction.qll‎

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private import internal.IRInternal
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private import internal.IRFunctionImports as Imports
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import Imports::IRFunctionBase
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import Instruction
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private newtype TIRFunction =
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MkIRFunction(Language::Function func) { Construction::functionHasIR(func) }
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/**
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* Represents the IR for a function.
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* The IR for a function.
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*/
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class IRFunction extends TIRFunction {
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Language::Function func;
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IRFunction() { this = MkIRFunction(func) }
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final string toString() { result = "IR: " + func.toString() }
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/**
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* Gets the function whose IR is represented.
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*/
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final Language::Function getFunction() { result = func }
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/**
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* Gets the location of the function.
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*/
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final Language::Location getLocation() { result = func.getLocation() }
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class IRFunction extends IRFunctionBase {
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/**
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* Gets the entry point for this function.
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*/

‎cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/Instruction.qll‎

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@@ -29,7 +29,13 @@ private Instruction getAnInstructionAtLine(IRFunction irFunc, Language::File fil
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/**
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* Represents a single operation in the IR.
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*/
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class Instruction extends Construction::TInstruction {
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class Instruction extends Construction::TStageInstruction {
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Instruction() {
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// The base `TStageInstruction` type is a superset of the actual instructions appearing in this
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// stage. This call lets the stage filter out the ones that are not reused from raw IR.
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Construction::hasInstruction(this)
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}
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final string toString() { result = getOpcode().toString() + ": " + getAST().toString() }
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/**
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* result of the `Load` instruction is a prvalue of type `int`, representing
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* the integer value loaded from variable `x`.
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*/
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final predicate isGLValue() { Construction::getInstructionResultType(this).hasType(_, true) }
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final predicate isGLValue() { getResultLanguageType().hasType(_, true) }
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/**
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* Gets the size of the result produced by this instruction, in bytes. If the
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* If `this.isGLValue()` holds for this instruction, the value of
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* `getResultSize()` will always be the size of a pointer.
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*/
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final int getResultSize() { result = Construction::getInstructionResultType(this).getByteSize() }
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final int getResultSize() { result = getResultLanguageType().getByteSize() }
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/**
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* Gets the opcode that specifies the operation performed by this instruction.

‎cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/IRFunctionImports.qll‎

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import semmle.code.cpp.ir.implementation.internal.IRFunctionBase as IRFunctionBase

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