[llvm] [CodeGen][NFC] Compute MaximumLegalStoreInBits just once (PR #189355)

[Alexis Engelke via llvm-commits]

https://github.com/aengelke created https://github.com/llvm/llvm-project/pull/189355

Instead of iterating over all value types per basic block, pre-compute
the TLI-specific value once when constructing the TLI.


>From bfac1d8d70758fa53c1f753d9ee855676773c969 Mon Sep 17 00:00:00 2001
From: Alexis Engelke <engelke at in.tum.de>
Date: Mon, 30 Mar 2026 11:00:44 +0000
Subject: [PATCH] [spr] initial version

Created using spr 1.3.8-wip
---
 llvm/include/llvm/CodeGen/TargetLowering.h    |  8 ++++++++
 llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 20 +++++--------------
 llvm/lib/CodeGen/TargetLoweringBase.cpp       |  7 +++++++
 3 files changed, 20 insertions(+), 15 deletions(-)

diff --git a/llvm/include/llvm/CodeGen/TargetLowering.h b/llvm/include/llvm/CodeGen/TargetLowering.h
index 2e66f574981ab..1f62f61269a16 100644
--- a/llvm/include/llvm/CodeGen/TargetLowering.h
+++ b/llvm/include/llvm/CodeGen/TargetLowering.h
@@ -2084,6 +2084,10 @@ class LLVM_ABI TargetLoweringBase {
   /// Retuen the minimum of largest number of comparisons in BitTest.
   unsigned getMinimumBitTestCmps() const;
 
+  unsigned getMaximumLegalStoreInBits() const {
+    return MaximumLegalStoreInBits;
+  }
+
   /// If a physical register, this specifies the register that
   /// llvm.savestack/llvm.restorestack should save and restore.
   Register getStackPointerRegisterToSaveRestore() const {
@@ -3767,6 +3771,10 @@ class LLVM_ABI TargetLoweringBase {
   /// The minimum of largest number of comparisons to use bit test for switch.
   unsigned MinimumBitTestCmps;
 
+  /// Maximum known legal store size, which can be guaranteed for scalable
+  /// vector.
+  unsigned MaximumLegalStoreInBits;
+
   /// This indicates if the target supports unaligned atomic operations.
   bool SupportsUnalignedAtomics;
 
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 9134a940f217b..971054e7f5032 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -260,15 +260,6 @@ namespace {
       ForCodeSize = DAG.shouldOptForSize();
       DisableGenericCombines =
           DisableCombines || (STI && STI->disableGenericCombines(OptLevel));
-
-      MaximumLegalStoreInBits = 0;
-      // We use the minimum store size here, since that's all we can guarantee
-      // for the scalable vector types.
-      for (MVT VT : MVT::all_valuetypes())
-        if (EVT(VT).isSimple() && VT != MVT::Other &&
-            TLI.isTypeLegal(EVT(VT)) &&
-            VT.getSizeInBits().getKnownMinValue() >= MaximumLegalStoreInBits)
-          MaximumLegalStoreInBits = VT.getSizeInBits().getKnownMinValue();
     }
 
     void ConsiderForPruning(SDNode *N) {
@@ -344,8 +335,6 @@ namespace {
     void CommitTargetLoweringOpt(const TargetLowering::TargetLoweringOpt &TLO);
 
   private:
-    unsigned MaximumLegalStoreInBits;
-
     /// Check the specified integer node value to see if it can be simplified or
     /// if things it uses can be simplified by bit propagation.
     /// If so, return true.
@@ -22718,7 +22707,7 @@ bool DAGCombiner::tryStoreMergeOfConstants(
       unsigned IsFast = 0;
 
       // Break early when size is too large to be legal.
-      if (StoreTy.getSizeInBits() > MaximumLegalStoreInBits)
+      if (StoreTy.getSizeInBits() > TLI.getMaximumLegalStoreInBits())
         break;
 
       if (TLI.isTypeLegal(StoreTy) &&
@@ -22826,7 +22815,7 @@ bool DAGCombiner::tryStoreMergeOfExtracts(
       unsigned IsFast = 0;
 
       // Break early when size is too large to be legal.
-      if (Ty.getSizeInBits() > MaximumLegalStoreInBits)
+      if (Ty.getSizeInBits() > TLI.getMaximumLegalStoreInBits())
         break;
 
       if (TLI.isTypeLegal(Ty) &&
@@ -22973,7 +22962,7 @@ bool DAGCombiner::tryStoreMergeOfLoads(SmallVectorImpl<MemOpLink> &StoreNodes,
       EVT StoreTy = EVT::getVectorVT(Context, MemVT.getScalarType(), Elts);
 
       // Break early when size is too large to be legal.
-      if (StoreTy.getSizeInBits() > MaximumLegalStoreInBits)
+      if (StoreTy.getSizeInBits() > TLI.getMaximumLegalStoreInBits())
         break;
 
       unsigned IsFastSt = 0;
@@ -23193,7 +23182,8 @@ bool DAGCombiner::mergeConsecutiveStores(StoreSDNode *St) {
   EVT MemVT = St->getMemoryVT();
   if (MemVT.isScalableVT())
     return false;
-  if (!MemVT.isSimple() || MemVT.getSizeInBits() * 2 > MaximumLegalStoreInBits)
+  if (!MemVT.isSimple() ||
+      MemVT.getSizeInBits() * 2 > TLI.getMaximumLegalStoreInBits())
     return false;
 
   // This function cannot currently deal with non-byte-sized memory sizes.
diff --git a/llvm/lib/CodeGen/TargetLoweringBase.cpp b/llvm/lib/CodeGen/TargetLoweringBase.cpp
index b6d5a4c22e133..0cb9ebc66fdd1 100644
--- a/llvm/lib/CodeGen/TargetLoweringBase.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringBase.cpp
@@ -1939,6 +1939,13 @@ void TargetLoweringBase::computeRegisterProperties(
     RepRegClassForVT[i] = RRC;
     RepRegClassCostForVT[i] = Cost;
   }
+
+  // Compute minimum known-legal store size.
+  MaximumLegalStoreInBits = 0;
+  for (MVT VT : MVT::all_valuetypes())
+    if (EVT(VT).isSimple() && VT != MVT::Other && isTypeLegal(EVT(VT)) &&
+        VT.getSizeInBits().getKnownMinValue() >= MaximumLegalStoreInBits)
+      MaximumLegalStoreInBits = VT.getSizeInBits().getKnownMinValue();
 }
 
 EVT TargetLoweringBase::getSetCCResultType(const DataLayout &DL, LLVMContext &,