[PATCH] D35030: [DAG] Handle missing transform in fold of value extension case.

[Nirav Dave via Phabricator via llvm-commits]

niravd created this revision.

When pushing an extension of a constant bitwise operator on a load
into the load, change other uses of the load value if they exist to
prevent the old load from persisting.


https://reviews.llvm.org/D35030

Files:
  lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  test/CodeGen/X86/avx512-mask-op.ll


Index: test/CodeGen/X86/avx512-mask-op.ll
===================================================================
--- test/CodeGen/X86/avx512-mask-op.ll
+++ test/CodeGen/X86/avx512-mask-op.ll
@@ -1630,10 +1630,8 @@
 ; CHECK-LABEL: f1:
 ; CHECK:       ## BB#0: ## %entry
 ; CHECK-NEXT:    movzbl {{.*}}(%rip), %edi
-; CHECK-NEXT:    movl %edi, %eax
-; CHECK-NEXT:    xorb $1, %al
-; CHECK-NEXT:    movb %al, {{.*}}(%rip)
 ; CHECK-NEXT:    xorl $1, %edi
+; CHECK-NEXT:    movb %dil, {{.*}}(%rip)
 ; CHECK-NEXT:    jmp _f2 ## TAILCALL
 entry:
   %.b1 = load i1, i1* @f1.v, align 4
Index: lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -7193,6 +7193,12 @@
                                     N0.getOperand(0).getValueType(), ExtLoad);
         ExtendSetCCUses(SetCCs, Trunc, ExtLoad, DL, ISD::SIGN_EXTEND);
         CombineTo(N0.getOperand(0).getNode(), Trunc, ExtLoad.getValue(1));
+        // If N0 has multiple uses, change other uses as well.
+        if (!N0.hasOneUse()) {
+          SDValue TruncAnd =
+              DAG.getNode(ISD::TRUNCATE, DL, N0.getValueType(), And);
+          CombineTo(N0.getNode(), TruncAnd);
+        }
         return CombineTo(N, And); // Return N so it doesn't get rechecked!
       }
     }
@@ -7486,6 +7492,12 @@
                                     N0.getOperand(0).getValueType(), ExtLoad);
         ExtendSetCCUses(SetCCs, Trunc, ExtLoad, DL, ISD::ZERO_EXTEND);
         CombineTo(N0.getOperand(0).getNode(), Trunc, ExtLoad.getValue(1));
+        // If N0 has multiple uses, change other uses as well.
+        if (!N0.hasOneUse()) {
+          SDValue TruncAnd =
+              DAG.getNode(ISD::TRUNCATE, DL, N0.getValueType(), And);
+          CombineTo(N0.getNode(), TruncAnd);
+        }
         return CombineTo(N, And); // Return N so it doesn't get rechecked!
       }
     }


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