[DAG] Avoid deleting nodes before combining them.

niravhdave · niravhdave · commit 07871007aa32 · 2017-07-18T17:39:15.000Z
When replacing a node and it's operand, replacing the operand node may cause the deletion of the original node leading to an assertion failure. Case around these replacements to avoid this without relying on inspecting the DELETED_NODE opcode in various extend dagcombiner cases. Fixes PR32515. Reviewers: dbabokin, RKSimon, davide, chandlerc Subscribers: chandlerc, llvm-commits Differential Revision: https://reviews.llvm.org/D34095 llvm-svn: 308330
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -7171,7 +7171,11 @@ SDValue DAGCombiner::visitSIGN_EXTEND(SDNode *N) {
       SDValue Trunc = DAG.getNode(ISD::TRUNCATE, SDLoc(N0),
                                   N0.getValueType(), ExtLoad);
       ExtendSetCCUses(SetCCs, Trunc, ExtLoad, DL, ISD::SIGN_EXTEND);
-      CombineTo(N0.getNode(), Trunc, ExtLoad.getValue(1));
+      // If the load value is used only by N, replace it via CombineTo N.
+      if (N0.getValue(0).hasOneUse())
+        DAG.ReplaceAllUsesOfValueWith(SDValue(LN0, 1), ExtLoad.getValue(1));
+      else
+        CombineTo(LN0, Trunc, ExtLoad.getValue(1));
       return CombineTo(N, ExtLoad); // Return N so it doesn't get rechecked!
     }
   }
@@ -7229,7 +7233,11 @@ SDValue DAGCombiner::visitSIGN_EXTEND(SDNode *N) {
                                     SDLoc(N0.getOperand(0)),
                                     N0.getOperand(0).getValueType(), ExtLoad);
         ExtendSetCCUses(SetCCs, Trunc, ExtLoad, DL, ISD::SIGN_EXTEND);
-        CombineTo(N0.getOperand(0).getNode(), Trunc, ExtLoad.getValue(1));
+        // If the load value is used only by N, replace it via CombineTo N.
+        if (SDValue(LN0, 0).hasOneUse())
+          DAG.ReplaceAllUsesOfValueWith(SDValue(LN0, 1), ExtLoad.getValue(1));
+        else
+          CombineTo(LN0, Trunc, ExtLoad.getValue(1));
         return CombineTo(N, And); // Return N so it doesn't get rechecked!
       }
     }
@@ -7470,7 +7478,11 @@ SDValue DAGCombiner::visitZERO_EXTEND(SDNode *N) {
       SDValue Trunc = DAG.getNode(ISD::TRUNCATE, SDLoc(N0),
                                   N0.getValueType(), ExtLoad);
       ExtendSetCCUses(SetCCs, Trunc, ExtLoad, SDLoc(N), ISD::ZERO_EXTEND);
-      CombineTo(N0.getNode(), Trunc, ExtLoad.getValue(1));
+      // If the load value is used only by N, replace it via CombineTo N.
+      if (SDValue(LN0, 0).hasOneUse())
+        DAG.ReplaceAllUsesOfValueWith(SDValue(LN0, 1), ExtLoad.getValue(1));
+      else
+        CombineTo(LN0, Trunc, ExtLoad.getValue(1));
       return CombineTo(N, ExtLoad); // Return N so it doesn't get rechecked!
     }
   }
@@ -7522,7 +7534,11 @@ SDValue DAGCombiner::visitZERO_EXTEND(SDNode *N) {
                                     SDLoc(N0.getOperand(0)),
                                     N0.getOperand(0).getValueType(), ExtLoad);
         ExtendSetCCUses(SetCCs, Trunc, ExtLoad, DL, ISD::ZERO_EXTEND);
-        CombineTo(N0.getOperand(0).getNode(), Trunc, ExtLoad.getValue(1));
+        // If the load value is used only by N, replace it via CombineTo N.
+        if (SDValue(LN0, 0).hasOneUse())
+          DAG.ReplaceAllUsesOfValueWith(SDValue(LN0, 1), ExtLoad.getValue(1));
+        else
+          CombineTo(LN0, Trunc, ExtLoad.getValue(1));
         return CombineTo(N, And); // Return N so it doesn't get rechecked!
       }
     }
@@ -7695,13 +7711,16 @@ SDValue DAGCombiner::visitANY_EXTEND(SDNode *N) {
                                        LN0->getChain(),
                                        LN0->getBasePtr(), N0.getValueType(),
                                        LN0->getMemOperand());
-      CombineTo(N, ExtLoad);
       SDValue Trunc = DAG.getNode(ISD::TRUNCATE, SDLoc(N0),
                                   N0.getValueType(), ExtLoad);
-      CombineTo(N0.getNode(), Trunc, ExtLoad.getValue(1));
       ExtendSetCCUses(SetCCs, Trunc, ExtLoad, SDLoc(N),
                       ISD::ANY_EXTEND);
-      return SDValue(N, 0);   // Return N so it doesn't get rechecked!
+      // If the load value is used only by N, replace it via CombineTo N.
+      if (N0.hasOneUse())
+        DAG.ReplaceAllUsesOfValueWith(SDValue(LN0, 1), ExtLoad.getValue(1));
+      else
+        CombineTo(LN0, Trunc, ExtLoad.getValue(1));
+      return CombineTo(N, ExtLoad); // Return N so it doesn't get rechecked!
     }
   }
 
diff --git a/llvm/test/CodeGen/X86/avx512-mask-op.ll b/llvm/test/CodeGen/X86/avx512-mask-op.ll
@@ -1630,8 +1630,9 @@ define void @f1(i32 %c) {
 ; 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 {{.*}}(%rip), %al
+; CHECK-NEXT:    notb %al
+; CHECK-NEXT:    andb $1, %al
 ; CHECK-NEXT:    movb %al, {{.*}}(%rip)
 ; CHECK-NEXT:    xorl $1, %edi
 ; CHECK-NEXT:    jmp _f2 ## TAILCALL
diff --git a/llvm/test/CodeGen/X86/pr32515.ll b/llvm/test/CodeGen/X86/pr32515.ll
@@ -0,0 +1,29 @@
+; RUN: llc -O0 -mtriple=x86_64-unknown -mcpu=skx -o - %s
+; RUN: llc     -mtriple=x86_64-unknown -mcpu=skx -o - %s
+; RUN: llc -O0 -mtriple=i686-unknown   -mcpu=skx -o - %s
+; RUN: llc     -mtriple=i686-unknown   -mcpu=skx -o - %s
+; REQUIRES: asserts
+
+@var_26 = external global i16, align 2
+
+define void @foo() #0 {
+ %1 = alloca i16, align 2
+ %2 = load i16, i16* @var_26, align 2
+ %3 = zext i16 %2 to i32
+ %4 = icmp ne i32 %3, 7
+ %5 = zext i1 %4 to i16
+ store i16 %5, i16* %1, align 2
+ %6 = load i16, i16* @var_26, align 2
+ %7 = zext i16 %6 to i32
+ %8 = and i32 1, %7
+ %9 = shl i32 %8, 0
+ %10 = load i16, i16* @var_26, align 2
+ %11 = zext i16 %10 to i32
+ %12 = icmp ne i32 %11, 7
+ %13 = zext i1 %12 to i32
+ %14 = and i32 %9, %13
+ %15 = icmp ne i32 %14, 0
+ %16 = zext i1 %15 to i8
+ store i8 %16, i8* undef, align 1
+ unreachable
+ }
