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Diffstat (limited to 'llvm/lib/CodeGen/GlobalISel/Localizer.cpp')
-rw-r--r--llvm/lib/CodeGen/GlobalISel/Localizer.cpp65
1 files changed, 9 insertions, 56 deletions
diff --git a/llvm/lib/CodeGen/GlobalISel/Localizer.cpp b/llvm/lib/CodeGen/GlobalISel/Localizer.cpp
index 1c4a668e5f31..a07416d08614 100644
--- a/llvm/lib/CodeGen/GlobalISel/Localizer.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/Localizer.cpp
@@ -13,6 +13,7 @@
#include "llvm/ADT/DenseMap.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/InitializePasses.h"
#include "llvm/Support/Debug.h"
@@ -40,60 +41,6 @@ void Localizer::init(MachineFunction &MF) {
TTI = &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(MF.getFunction());
}
-bool Localizer::shouldLocalize(const MachineInstr &MI) {
- // Assuming a spill and reload of a value has a cost of 1 instruction each,
- // this helper function computes the maximum number of uses we should consider
- // for remat. E.g. on arm64 global addresses take 2 insts to materialize. We
- // break even in terms of code size when the original MI has 2 users vs
- // choosing to potentially spill. Any more than 2 users we we have a net code
- // size increase. This doesn't take into account register pressure though.
- auto maxUses = [](unsigned RematCost) {
- // A cost of 1 means remats are basically free.
- if (RematCost == 1)
- return UINT_MAX;
- if (RematCost == 2)
- return 2U;
-
- // Remat is too expensive, only sink if there's one user.
- if (RematCost > 2)
- return 1U;
- llvm_unreachable("Unexpected remat cost");
- };
-
- // Helper to walk through uses and terminate if we've reached a limit. Saves
- // us spending time traversing uses if all we want to know is if it's >= min.
- auto isUsesAtMost = [&](unsigned Reg, unsigned MaxUses) {
- unsigned NumUses = 0;
- auto UI = MRI->use_instr_nodbg_begin(Reg), UE = MRI->use_instr_nodbg_end();
- for (; UI != UE && NumUses < MaxUses; ++UI) {
- NumUses++;
- }
- // If we haven't reached the end yet then there are more than MaxUses users.
- return UI == UE;
- };
-
- switch (MI.getOpcode()) {
- default:
- return false;
- // Constants-like instructions should be close to their users.
- // We don't want long live-ranges for them.
- case TargetOpcode::G_CONSTANT:
- case TargetOpcode::G_FCONSTANT:
- case TargetOpcode::G_FRAME_INDEX:
- case TargetOpcode::G_INTTOPTR:
- return true;
- case TargetOpcode::G_GLOBAL_VALUE: {
- unsigned RematCost = TTI->getGISelRematGlobalCost();
- Register Reg = MI.getOperand(0).getReg();
- unsigned MaxUses = maxUses(RematCost);
- if (MaxUses == UINT_MAX)
- return true; // Remats are "free" so always localize.
- bool B = isUsesAtMost(Reg, MaxUses);
- return B;
- }
- }
-}
-
void Localizer::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<TargetTransformInfoWrapperPass>();
getSelectionDAGFallbackAnalysisUsage(AU);
@@ -119,9 +66,10 @@ bool Localizer::localizeInterBlock(MachineFunction &MF,
// we only localize instructions in the entry block here. This might change if
// we start doing CSE across blocks.
auto &MBB = MF.front();
+ auto &TL = *MF.getSubtarget().getTargetLowering();
for (auto RI = MBB.rbegin(), RE = MBB.rend(); RI != RE; ++RI) {
MachineInstr &MI = *RI;
- if (!shouldLocalize(MI))
+ if (!TL.shouldLocalize(MI, TTI))
continue;
LLVM_DEBUG(dbgs() << "Should localize: " << MI);
assert(MI.getDesc().getNumDefs() == 1 &&
@@ -138,8 +86,13 @@ bool Localizer::localizeInterBlock(MachineFunction &MF,
LLVM_DEBUG(MachineInstr &MIUse = *MOUse.getParent();
dbgs() << "Checking use: " << MIUse
<< " #Opd: " << MIUse.getOperandNo(&MOUse) << '\n');
- if (isLocalUse(MOUse, MI, InsertMBB))
+ if (isLocalUse(MOUse, MI, InsertMBB)) {
+ // Even if we're in the same block, if the block is very large we could
+ // still have many long live ranges. Try to do intra-block localization
+ // too.
+ LocalizedInstrs.insert(&MI);
continue;
+ }
LLVM_DEBUG(dbgs() << "Fixing non-local use\n");
Changed = true;
auto MBBAndReg = std::make_pair(InsertMBB, Reg);