[llvm] 1716924 - [Attributor][NFC] Introduce a flag to skip liveness checks

[Johannes Doerfert via llvm-commits]

Author: Johannes Doerfert
Date: 2023-06-29T09:18:36-07:00
New Revision: 1716924ccfddd3e394689a7b48d5e1a67cee450f

URL: https://github.com/llvm/llvm-project/commit/1716924ccfddd3e394689a7b48d5e1a67cee450f
DIFF: https://github.com/llvm/llvm-project/commit/1716924ccfddd3e394689a7b48d5e1a67cee450f.diff

LOG: [Attributor][NFC] Introduce a flag to skip liveness checks

While we can disallow AAs, liveness checks are everywhere and if the
user doesn't want them it is costly to go through just to find out
everything is assumed live.

Added: 
    

Modified: 
    llvm/include/llvm/Transforms/IPO/Attributor.h
    llvm/lib/Transforms/IPO/Attributor.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/Transforms/IPO/Attributor.h b/llvm/include/llvm/Transforms/IPO/Attributor.h
index af3f5edf59633..beb461a989f8b 100644
--- a/llvm/include/llvm/Transforms/IPO/Attributor.h
+++ b/llvm/include/llvm/Transforms/IPO/Attributor.h
@@ -1453,6 +1453,9 @@ struct AttributorConfig {
   /// function marked live. See also: InitializationCallback>
   bool DefaultInitializeLiveInternals = true;
 
+  /// Flag to determine if we should skip all liveness checks early on.
+  bool UseLiveness = true;
+
   /// Callback function to be invoked on internal functions marked live.
   std::function<void(Attributor &A, const Function &F)> InitializationCallback =
       nullptr;

diff  --git a/llvm/lib/Transforms/IPO/Attributor.cpp b/llvm/lib/Transforms/IPO/Attributor.cpp
index da83fc7e11e2e..d1a96f07175e3 100644
--- a/llvm/lib/Transforms/IPO/Attributor.cpp
+++ b/llvm/lib/Transforms/IPO/Attributor.cpp
@@ -1407,6 +1407,8 @@ bool Attributor::isAssumedDead(const AbstractAttribute &AA,
                                const AAIsDead *FnLivenessAA,
                                bool &UsedAssumedInformation,
                                bool CheckBBLivenessOnly, DepClassTy DepClass) {
+  if (!Configuration.UseLiveness)
+    return false;
   const IRPosition &IRP = AA.getIRPosition();
   if (!Functions.count(IRP.getAnchorScope()))
     return false;
@@ -1419,6 +1421,8 @@ bool Attributor::isAssumedDead(const Use &U,
                                const AAIsDead *FnLivenessAA,
                                bool &UsedAssumedInformation,
                                bool CheckBBLivenessOnly, DepClassTy DepClass) {
+  if (!Configuration.UseLiveness)
+    return false;
   Instruction *UserI = dyn_cast<Instruction>(U.getUser());
   if (!UserI)
     return isAssumedDead(IRPosition::value(*U.get()), QueryingAA, FnLivenessAA,
@@ -1467,6 +1471,8 @@ bool Attributor::isAssumedDead(const Instruction &I,
                                bool &UsedAssumedInformation,
                                bool CheckBBLivenessOnly, DepClassTy DepClass,
                                bool CheckForDeadStore) {
+  if (!Configuration.UseLiveness)
+    return false;
   const IRPosition::CallBaseContext *CBCtx =
       QueryingAA ? QueryingAA->getCallBaseContext() : nullptr;
 
@@ -1527,6 +1533,8 @@ bool Attributor::isAssumedDead(const IRPosition &IRP,
                                const AAIsDead *FnLivenessAA,
                                bool &UsedAssumedInformation,
                                bool CheckBBLivenessOnly, DepClassTy DepClass) {
+  if (!Configuration.UseLiveness)
+    return false;
   // Don't check liveness for constants, e.g. functions, used as (floating)
   // values since the context instruction and such is here meaningless.
   if (IRP.getPositionKind() == IRPosition::IRP_FLOAT &&
@@ -1572,6 +1580,8 @@ bool Attributor::isAssumedDead(const BasicBlock &BB,
                                const AbstractAttribute *QueryingAA,
                                const AAIsDead *FnLivenessAA,
                                DepClassTy DepClass) {
+  if (!Configuration.UseLiveness)
+    return false;
   const Function &F = *BB.getParent();
   if (!FnLivenessAA || FnLivenessAA->getAnchorScope() != &F)
     FnLivenessAA = getOrCreateAAFor<AAIsDead>(IRPosition::function(F),