[DAG] Avoid deleting nodes before combining them.

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

3 files changed, 58 insertions, 9 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index d526dfd0cc4..f2ecdbe253e 100644
--- 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
index e1a92c60d18..6f4bf061a21 100644
--- 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
new file mode 100644
index 00000000000..aeb6803867a
--- /dev/null
+++ 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
+ }