diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 58d8ce2f1e67d..5e0755e47bbfb 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -2436,6 +2436,16 @@ SDValue SelectionDAG::FoldSetCC(EVT VT, SDValue N1, SDValue N2,
                                 ISD::CondCode Cond, const SDLoc &dl) {
   EVT OpVT = N1.getValueType();
 
+  auto GetUndefBooleanConstant = [&]() {
+    if (VT.getScalarType() == MVT::i1 ||
+        TLI->getBooleanContents(OpVT) ==
+            TargetLowering::UndefinedBooleanContent)
+      return getUNDEF(VT);
+    // ZeroOrOne / ZeroOrNegative require specific values for the high bits,
+    // so we cannot use getUNDEF(). Return zero instead.
+    return getConstant(0, dl, VT);
+  };
+
   // These setcc operations always fold.
   switch (Cond) {
   default: break;
@@ -2465,12 +2475,12 @@ SDValue SelectionDAG::FoldSetCC(EVT VT, SDValue N1, SDValue N2,
     // icmp eq/ne X, undef -> undef.
     if ((N1.isUndef() || N2.isUndef()) &&
         (Cond == ISD::SETEQ || Cond == ISD::SETNE))
-      return getUNDEF(VT);
+      return GetUndefBooleanConstant();
 
     // If both operands are undef, we can return undef for int comparison.
     // icmp undef, undef -> undef.
     if (N1.isUndef() && N2.isUndef())
-      return getUNDEF(VT);
+      return GetUndefBooleanConstant();
 
     // icmp X, X -> true/false
     // icmp X, undef -> true/false because undef could be X.
@@ -2496,34 +2506,34 @@ SDValue SelectionDAG::FoldSetCC(EVT VT, SDValue N1, SDValue N2,
     switch (Cond) {
     default: break;
     case ISD::SETEQ:  if (R==APFloat::cmpUnordered)
-                        return getUNDEF(VT);
+                        return GetUndefBooleanConstant();
                       [[fallthrough]];
     case ISD::SETOEQ: return getBoolConstant(R==APFloat::cmpEqual, dl, VT,
                                              OpVT);
     case ISD::SETNE:  if (R==APFloat::cmpUnordered)
-                        return getUNDEF(VT);
+                        return GetUndefBooleanConstant();
                       [[fallthrough]];
     case ISD::SETONE: return getBoolConstant(R==APFloat::cmpGreaterThan ||
                                              R==APFloat::cmpLessThan, dl, VT,
                                              OpVT);
     case ISD::SETLT:  if (R==APFloat::cmpUnordered)
-                        return getUNDEF(VT);
+                        return GetUndefBooleanConstant();
                       [[fallthrough]];
     case ISD::SETOLT: return getBoolConstant(R==APFloat::cmpLessThan, dl, VT,
                                              OpVT);
     case ISD::SETGT:  if (R==APFloat::cmpUnordered)
-                        return getUNDEF(VT);
+                        return GetUndefBooleanConstant();
                       [[fallthrough]];
     case ISD::SETOGT: return getBoolConstant(R==APFloat::cmpGreaterThan, dl,
                                              VT, OpVT);
     case ISD::SETLE:  if (R==APFloat::cmpUnordered)
-                        return getUNDEF(VT);
+                        return GetUndefBooleanConstant();
                       [[fallthrough]];
     case ISD::SETOLE: return getBoolConstant(R==APFloat::cmpLessThan ||
                                              R==APFloat::cmpEqual, dl, VT,
                                              OpVT);
     case ISD::SETGE:  if (R==APFloat::cmpUnordered)
-                        return getUNDEF(VT);
+                        return GetUndefBooleanConstant();
                       [[fallthrough]];
     case ISD::SETOGE: return getBoolConstant(R==APFloat::cmpGreaterThan ||
                                          R==APFloat::cmpEqual, dl, VT, OpVT);
@@ -2568,7 +2578,7 @@ SDValue SelectionDAG::FoldSetCC(EVT VT, SDValue N1, SDValue N2,
     case 1: // Known true.
       return getBoolConstant(true, dl, VT, OpVT);
     case 2: // Undefined.
-      return getUNDEF(VT);
+      return GetUndefBooleanConstant();
     }
   }
 
diff --git a/llvm/test/CodeGen/X86/avx512-insert-extract.ll b/llvm/test/CodeGen/X86/avx512-insert-extract.ll
index f3e73c4fd85d5..89b245b4ca8ef 100644
--- a/llvm/test/CodeGen/X86/avx512-insert-extract.ll
+++ b/llvm/test/CodeGen/X86/avx512-insert-extract.ll
@@ -1878,10 +1878,11 @@ define i96 @test_insertelement_variable_v96i1(<96 x i8> %a, i8 %b, i32 %index) n
 ; KNL-NEXT:    vpinsrb $14, 720(%rbp), %xmm3, %xmm3
 ; KNL-NEXT:    vpinsrb $15, 728(%rbp), %xmm3, %xmm3
 ; KNL-NEXT:    vinserti128 $1, %xmm3, %ymm2, %ymm2
-; KNL-NEXT:    vpcmpeqb %ymm0, %ymm2, %ymm0
-; KNL-NEXT:    vpternlogq $15, %zmm0, %zmm0, %zmm0
+; KNL-NEXT:    vpcmpeqb %ymm0, %ymm2, %ymm2
+; KNL-NEXT:    vpternlogq $15, %zmm2, %zmm2, %zmm2
 ; KNL-NEXT:    cmpb $0, 736(%rbp)
 ; KNL-NEXT:    vmovdqa %ymm0, {{[0-9]+}}(%rsp)
+; KNL-NEXT:    vmovdqa %ymm2, {{[0-9]+}}(%rsp)
 ; KNL-NEXT:    vmovdqa64 %zmm1, (%rsp)
 ; KNL-NEXT:    setne (%rsp,%rax)
 ; KNL-NEXT:    vpmovsxbd (%rsp), %zmm0
diff --git a/llvm/test/CodeGen/X86/setcc.ll b/llvm/test/CodeGen/X86/setcc.ll
index cd28df0a1244c..c38318d5f6a25 100644
--- a/llvm/test/CodeGen/X86/setcc.ll
+++ b/llvm/test/CodeGen/X86/setcc.ll
@@ -339,17 +339,16 @@ define i32 @PR55138(i32 %x) {
   ret i32 %and
 }
 
-; FIXME: Miscompile.
 define i64 @pr63055(double %arg) {
 ; X86-LABEL: pr63055:
 ; X86:       ## %bb.0:
-; X86-NEXT:    movl $255, %eax
+; X86-NEXT:    movl $1, %eax
 ; X86-NEXT:    xorl %edx, %edx
 ; X86-NEXT:    retl
 ;
 ; X64-LABEL: pr63055:
 ; X64:       ## %bb.0:
-; X64-NEXT:    movl $255, %eax
+; X64-NEXT:    movl $1, %eax
 ; X64-NEXT:    retq
   %fcmp = fcmp une double 0x7FF8000000000000, %arg
   %ext = zext i1 %fcmp to i64