[PATCH] D133485: [LICM] Allow promotion with non-load/store users

[Nikita Popov via Phabricator via llvm-commits]

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If there are non-load/store users of the promoted pointer, we currently abort promotion. However, having such users isn't really relevant to the transform. We already separately check that a) there are no instructions that modref the promoted pointer and b) that a pointer capture disables store promotion.

In the affected `@test_captured_in_loop` test case we have a readnone capture of the promoted pointer, which means that load promotion can be performed (while store promotion cannot).


https://reviews.llvm.org/D133485

Files:
  llvm/lib/Transforms/Scalar/LICM.cpp
  llvm/test/Transforms/LICM/promote-capture.ll


Index: llvm/test/Transforms/LICM/promote-capture.ll
===================================================================
--- llvm/test/Transforms/LICM/promote-capture.ll
+++ llvm/test/Transforms/LICM/promote-capture.ll
@@ -61,18 +61,20 @@
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[COUNT:%.*]] = alloca i32, align 4
 ; CHECK-NEXT:    store i32 0, i32* [[COUNT]], align 4
+; CHECK-NEXT:    [[COUNT_PROMOTED:%.*]] = load i32, i32* [[COUNT]], align 4
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop:
-; CHECK-NEXT:    [[I:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[I_NEXT:%.*]], [[LATCH:%.*]] ]
+; CHECK-NEXT:    [[C_INC2:%.*]] = phi i32 [ [[COUNT_PROMOTED]], [[ENTRY:%.*]] ], [ [[C_INC1:%.*]], [[LATCH:%.*]] ]
+; CHECK-NEXT:    [[I:%.*]] = phi i32 [ 0, [[ENTRY]] ], [ [[I_NEXT:%.*]], [[LATCH]] ]
 ; CHECK-NEXT:    [[COND:%.*]] = call i1 @cond(i32 [[I]])
 ; CHECK-NEXT:    br i1 [[COND]], label [[IF:%.*]], label [[LATCH]]
 ; CHECK:       if:
-; CHECK-NEXT:    [[C:%.*]] = load i32, i32* [[COUNT]], align 4
-; CHECK-NEXT:    [[C_INC:%.*]] = add i32 [[C]], 1
+; CHECK-NEXT:    [[C_INC:%.*]] = add i32 [[C_INC2]], 1
 ; CHECK-NEXT:    store i32 [[C_INC]], i32* [[COUNT]], align 4
 ; CHECK-NEXT:    call void @capture(i32* [[COUNT]])
 ; CHECK-NEXT:    br label [[LATCH]]
 ; CHECK:       latch:
+; CHECK-NEXT:    [[C_INC1]] = phi i32 [ [[C_INC]], [[IF]] ], [ [[C_INC2]], [[LOOP]] ]
 ; CHECK-NEXT:    [[I_NEXT]] = add nuw i32 [[I]], 1
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[I_NEXT]], [[LEN:%.*]]
 ; CHECK-NEXT:    br i1 [[CMP]], label [[EXIT:%.*]], label [[LOOP]]
Index: llvm/lib/Transforms/Scalar/LICM.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/LICM.cpp
+++ llvm/lib/Transforms/Scalar/LICM.cpp
@@ -2093,7 +2093,7 @@
               Store->getAlign(), MDL, Preheader->getTerminator(), DT, TLI);
         }
       } else
-        return false; // Not a load or store.
+        continue; // Not a load or store.
 
       if (!AccessTy)
         AccessTy = getLoadStoreType(UI);


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