[llvm] 1ddc719 - Revert "[LICM] Only create load in pre-header when promoting load."

[Florian Hahn via llvm-commits]

Author: Florian Hahn
Date: 2022-04-11T17:37:23+02:00
New Revision: 1ddc719680c21f3d1e75827665b9b40bf75256f4

URL: https://github.com/llvm/llvm-project/commit/1ddc719680c21f3d1e75827665b9b40bf75256f4
DIFF: https://github.com/llvm/llvm-project/commit/1ddc719680c21f3d1e75827665b9b40bf75256f4.diff

LOG: Revert "[LICM] Only create load in pre-header when promoting load."

This reverts commit 42229b96bf94ec896d5c62fa643d83ba96e86eea.

This appears to cause crashes on multiple bots.

Added: 
    

Modified: 
    llvm/lib/Transforms/Scalar/LICM.cpp
    llvm/test/Transforms/LICM/scalar-promote.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Scalar/LICM.cpp b/llvm/lib/Transforms/Scalar/LICM.cpp
index 2f036d676e8e9..74ae5977a3663 100644
--- a/llvm/lib/Transforms/Scalar/LICM.cpp
+++ b/llvm/lib/Transforms/Scalar/LICM.cpp
@@ -2156,24 +2156,21 @@ bool llvm::promoteLoopAccessesToScalars(
 
   // Set up the preheader to have a definition of the value.  It is the live-out
   // value from the preheader that uses in the loop will use.
-  LoadInst *PreheaderLoad = nullptr;
-  if (FoundLoadToPromote) {
-    PreheaderLoad =
-        new LoadInst(AccessTy, SomePtr, SomePtr->getName() + ".promoted",
-                     Preheader->getTerminator());
-    if (SawUnorderedAtomic)
-      PreheaderLoad->setOrdering(AtomicOrdering::Unordered);
-    PreheaderLoad->setAlignment(Alignment);
-    PreheaderLoad->setDebugLoc(DebugLoc());
-    if (AATags)
-      PreheaderLoad->setAAMetadata(AATags);
-
-    MemoryAccess *PreheaderLoadMemoryAccess = MSSAU.createMemoryAccessInBB(
-        PreheaderLoad, nullptr, PreheaderLoad->getParent(), MemorySSA::End);
-    MemoryUse *NewMemUse = cast<MemoryUse>(PreheaderLoadMemoryAccess);
-    MSSAU.insertUse(NewMemUse, /*RenameUses=*/true);
-    SSA.AddAvailableValue(Preheader, PreheaderLoad);
-  }
+  LoadInst *PreheaderLoad = new LoadInst(
+      AccessTy, SomePtr, SomePtr->getName() + ".promoted",
+      Preheader->getTerminator());
+  if (SawUnorderedAtomic)
+    PreheaderLoad->setOrdering(AtomicOrdering::Unordered);
+  PreheaderLoad->setAlignment(Alignment);
+  PreheaderLoad->setDebugLoc(DebugLoc());
+  if (AATags)
+    PreheaderLoad->setAAMetadata(AATags);
+  SSA.AddAvailableValue(Preheader, PreheaderLoad);
+
+  MemoryAccess *PreheaderLoadMemoryAccess = MSSAU.createMemoryAccessInBB(
+      PreheaderLoad, nullptr, PreheaderLoad->getParent(), MemorySSA::End);
+  MemoryUse *NewMemUse = cast<MemoryUse>(PreheaderLoadMemoryAccess);
+  MSSAU.insertUse(NewMemUse, /*RenameUses=*/true);
 
   if (VerifyMemorySSA)
     MSSAU.getMemorySSA()->verifyMemorySSA();
@@ -2184,7 +2181,7 @@ bool llvm::promoteLoopAccessesToScalars(
   if (VerifyMemorySSA)
     MSSAU.getMemorySSA()->verifyMemorySSA();
   // If the SSAUpdater didn't use the load in the preheader, just zap it now.
-  if (PreheaderLoad && PreheaderLoad->use_empty())
+  if (PreheaderLoad->use_empty())
     eraseInstruction(*PreheaderLoad, *SafetyInfo, MSSAU);
 
   return true;

diff  --git a/llvm/test/Transforms/LICM/scalar-promote.ll b/llvm/test/Transforms/LICM/scalar-promote.ll
index 78cbbeb2c9c20..ad60bc87b910a 100644
--- a/llvm/test/Transforms/LICM/scalar-promote.ll
+++ b/llvm/test/Transforms/LICM/scalar-promote.ll
@@ -605,9 +605,10 @@ Out:
 define void @test_sink_store_only() writeonly {
 ; CHECK-LABEL: @test_sink_store_only(
 ; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[GLB_PROMOTED:%.*]] = load i8, i8* @glb, align 1
 ; CHECK-NEXT:    br label [[LOOP_HEADER:%.*]]
 ; CHECK:       loop.header:
-; CHECK-NEXT:    [[DIV1:%.*]] = phi i8 [ undef, [[ENTRY:%.*]] ], [ [[DIV:%.*]], [[LOOP_LATCH:%.*]] ]
+; CHECK-NEXT:    [[DIV1:%.*]] = phi i8 [ [[GLB_PROMOTED]], [[ENTRY:%.*]] ], [ [[DIV:%.*]], [[LOOP_LATCH:%.*]] ]
 ; CHECK-NEXT:    [[I:%.*]] = phi i8 [ 0, [[ENTRY]] ], [ [[ADD:%.*]], [[LOOP_LATCH]] ]
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i8 [[I]], 4
 ; CHECK-NEXT:    br i1 [[CMP]], label [[LOOP_LATCH]], label [[EXIT:%.*]]