RegAlloc superpass: includes phi elimination, coalescing, and scheduling.
Creates a configurable regalloc pipeline.
Ensure specific llc options do what they say and nothing more: -reglloc=... has no effect other than selecting the allocator pass itself. This patch introduces a new umbrella flag, "-optimize-regalloc", to enable/disable the optimizing regalloc "superpass". This allows for example testing coalscing and scheduling under -O0 or vice-versa.
When a CodeGen pass requires the MachineFunction to have a particular property, we need to explicitly define that property so it can be directly queried rather than naming a specific Pass. For example, to check for SSA, use MRI->isSSA, not addRequired<PHIElimination>.
CodeGen transformation passes are never "required" as an analysis
ProcessImplicitDefs does not require LiveVariables.
We have a plan to massively simplify some of the early passes within the regalloc superpass.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@150226 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/Passes.cpp b/lib/CodeGen/Passes.cpp
index b547c0f..5a7ec66 100644
--- a/lib/CodeGen/Passes.cpp
+++ b/lib/CodeGen/Passes.cpp
@@ -51,6 +51,13 @@
cl::desc("Disable Machine LICM"));
static cl::opt<bool> DisableMachineCSE("disable-machine-cse", cl::Hidden,
cl::desc("Disable Machine Common Subexpression Elimination"));
+static cl::opt<cl::boolOrDefault>
+OptimizeRegAlloc("optimize-regalloc", cl::Hidden,
+ cl::desc("Enable optimized register allocation compilation path."));
+static cl::opt<bool> EnableMachineSched("enable-misched", cl::Hidden,
+ cl::desc("Enable the machine instruction scheduling pass."));
+static cl::opt<bool> EnableStrongPHIElim("strong-phi-elim", cl::Hidden,
+ cl::desc("Use strong PHI elimination."));
static cl::opt<bool> DisablePostRAMachineLICM("disable-postra-machine-licm",
cl::Hidden,
cl::desc("Disable Machine LICM"));
@@ -225,7 +232,10 @@
// Run register allocation and passes that are tightly coupled with it,
// including phi elimination and scheduling.
- addRegAlloc();
+ if (getOptimizeRegAlloc())
+ addOptimizedRegAlloc(createRegAllocPass(true));
+ else
+ addFastRegAlloc(createRegAllocPass(false));
// Run post-ra passes.
if (addPostRegAlloc())
@@ -306,71 +316,138 @@
/// Register Allocation Pass Configuration
//===---------------------------------------------------------------------===//
+bool TargetPassConfig::getOptimizeRegAlloc() const {
+ switch (OptimizeRegAlloc) {
+ case cl::BOU_UNSET: return getOptLevel() != CodeGenOpt::None;
+ case cl::BOU_TRUE: return true;
+ case cl::BOU_FALSE: return false;
+ }
+ llvm_unreachable("Invalid optimize-regalloc state");
+}
+
/// RegisterRegAlloc's global Registry tracks allocator registration.
MachinePassRegistry RegisterRegAlloc::Registry;
/// A dummy default pass factory indicates whether the register allocator is
/// overridden on the command line.
-static FunctionPass *createDefaultRegisterAllocator() { return 0; }
+static FunctionPass *useDefaultRegisterAllocator() { return 0; }
static RegisterRegAlloc
defaultRegAlloc("default",
"pick register allocator based on -O option",
- createDefaultRegisterAllocator);
+ useDefaultRegisterAllocator);
/// -regalloc=... command line option.
static cl::opt<RegisterRegAlloc::FunctionPassCtor, false,
RegisterPassParser<RegisterRegAlloc> >
RegAlloc("regalloc",
- cl::init(&createDefaultRegisterAllocator),
+ cl::init(&useDefaultRegisterAllocator),
cl::desc("Register allocator to use"));
-/// createRegisterAllocator - choose the appropriate register allocator.
-FunctionPass *llvm::createRegisterAllocator(CodeGenOpt::Level OptLevel) {
+/// Instantiate the default register allocator pass for this target for either
+/// the optimized or unoptimized allocation path. This will be added to the pass
+/// manager by addFastRegAlloc in the unoptimized case or addOptimizedRegAlloc
+/// in the optimized case.
+///
+/// A target that uses the standard regalloc pass order for fast or optimized
+/// allocation may still override this for per-target regalloc
+/// selection. But -regalloc=... always takes precedence.
+FunctionPass *TargetPassConfig::createTargetRegisterAllocator(bool Optimized) {
+ if (Optimized)
+ return createGreedyRegisterAllocator();
+ else
+ return createFastRegisterAllocator();
+}
+
+/// Find and instantiate the register allocation pass requested by this target
+/// at the current optimization level. Different register allocators are
+/// defined as separate passes because they may require different analysis.
+///
+/// This helper ensures that the regalloc= option is always available,
+/// even for targets that override the default allocator.
+///
+/// FIXME: When MachinePassRegistry register pass IDs instead of function ptrs,
+/// this can be folded into addPass.
+FunctionPass *TargetPassConfig::createRegAllocPass(bool Optimized) {
RegisterRegAlloc::FunctionPassCtor Ctor = RegisterRegAlloc::getDefault();
+ // Initialize the global default.
if (!Ctor) {
Ctor = RegAlloc;
RegisterRegAlloc::setDefault(RegAlloc);
}
-
- if (Ctor != createDefaultRegisterAllocator)
+ if (Ctor != useDefaultRegisterAllocator)
return Ctor();
- // When the 'default' allocator is requested, pick one based on OptLevel.
- switch (OptLevel) {
- case CodeGenOpt::None:
- return createFastRegisterAllocator();
- default:
- return createGreedyRegisterAllocator();
- }
+ // With no -regalloc= override, ask the target for a regalloc pass.
+ return createTargetRegisterAllocator(Optimized);
+}
+
+/// Add the minimum set of target-independent passes that are required for
+/// register allocation. No coalescing or scheduling.
+void TargetPassConfig::addFastRegAlloc(FunctionPass *RegAllocPass) {
+ addPass(PHIEliminationID);
+ addPass(TwoAddressInstructionPassID);
+
+ PM.add(RegAllocPass);
+ printAndVerify("After Register Allocation");
}
/// Add standard target-independent passes that are tightly coupled with
-/// register allocation, including coalescing, machine instruction scheduling,
-/// and register allocation itself.
-///
-/// FIXME: This will become the register allocation "super pass" pipeline.
-void TargetPassConfig::addRegAlloc() {
- // Perform register allocation.
- PM.add(createRegisterAllocator(getOptLevel()));
+/// optimized register allocation, including coalescing, machine instruction
+/// scheduling, and register allocation itself.
+void TargetPassConfig::addOptimizedRegAlloc(FunctionPass *RegAllocPass) {
+ // LiveVariables currently requires pure SSA form.
+ //
+ // FIXME: Once TwoAddressInstruction pass no longer uses kill flags,
+ // LiveVariables can be removed completely, and LiveIntervals can be directly
+ // computed. (We still either need to regenerate kill flags after regalloc, or
+ // preferably fix the scavenger to not depend on them).
+ addPass(LiveVariablesID);
+
+ // Add passes that move from transformed SSA into conventional SSA. This is a
+ // "copy coalescing" problem.
+ //
+ if (!EnableStrongPHIElim) {
+ // Edge splitting is smarter with machine loop info.
+ addPass(MachineLoopInfoID);
+ addPass(PHIEliminationID);
+ }
+ addPass(TwoAddressInstructionPassID);
+
+ // FIXME: Either remove this pass completely, or fix it so that it works on
+ // SSA form. We could modify LiveIntervals to be independent of this pass, But
+ // it would be even better to simply eliminate *all* IMPLICIT_DEFs before
+ // leaving SSA.
+ addPass(ProcessImplicitDefsID);
+
+ if (EnableStrongPHIElim)
+ addPass(StrongPHIEliminationID);
+
+ addPass(RegisterCoalescerID);
+
+ // PreRA instruction scheduling.
+ if (EnableMachineSched)
+ addPass(MachineSchedulerID);
+
+ // Add the selected register allocation pass.
+ PM.add(RegAllocPass);
printAndVerify("After Register Allocation");
// Perform stack slot coloring and post-ra machine LICM.
- if (getOptLevel() != CodeGenOpt::None) {
- // FIXME: Re-enable coloring with register when it's capable of adding
- // kill markers.
- if (!DisableSSC)
- addPass(StackSlotColoringID);
+ //
+ // FIXME: Re-enable coloring with register when it's capable of adding
+ // kill markers.
+ if (!DisableSSC)
+ addPass(StackSlotColoringID);
- // Run post-ra machine LICM to hoist reloads / remats.
- //
- // FIXME: can this move into MachineLateOptimization?
- if (!DisablePostRAMachineLICM)
- addPass(MachineLICMID);
+ // Run post-ra machine LICM to hoist reloads / remats.
+ //
+ // FIXME: can this move into MachineLateOptimization?
+ if (!DisablePostRAMachineLICM)
+ addPass(MachineLICMID);
- printAndVerify("After StackSlotColoring and postra Machine LICM");
- }
+ printAndVerify("After StackSlotColoring and postra Machine LICM");
}
//===---------------------------------------------------------------------===//