diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -2867,11 +2867,12 @@
     MI.RemoveOperand(1);
     Observer.changedInstr(MI);
 
-    MIRBuilder.setInsertPt(MIRBuilder.getMBB(), ++MIRBuilder.getInsertPt());
-
     auto HiPart = MIRBuilder.buildInstr(Opcode, {Ty}, {LHS, RHS});
     auto Zero = MIRBuilder.buildConstant(Ty, 0);
 
+    // Move insert point forward so we can use the Res register if needed.
+    MIRBuilder.setInsertPt(MIRBuilder.getMBB(), ++MIRBuilder.getInsertPt());
+
     // For *signed* multiply, overflow is detected by checking:
     // (hi != (lo >> bitwidth-1))
     if (Opcode == TargetOpcode::G_SMULH) {
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/legalize-mul.mir b/llvm/test/CodeGen/AArch64/GlobalISel/legalize-mul.mir
--- a/llvm/test/CodeGen/AArch64/GlobalISel/legalize-mul.mir
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/legalize-mul.mir
@@ -28,8 +28,8 @@
     ; CHECK-LABEL: name: test_smul_overflow
     ; CHECK: [[COPY:%[0-9]+]]:_(s64) = COPY $x0
     ; CHECK: [[COPY1:%[0-9]+]]:_(s64) = COPY $x1
-    ; CHECK: [[MUL:%[0-9]+]]:_(s64) = G_MUL [[COPY]], [[COPY1]]
     ; CHECK: [[SMULH:%[0-9]+]]:_(s64) = G_SMULH [[COPY]], [[COPY1]]
+    ; CHECK: [[MUL:%[0-9]+]]:_(s64) = G_MUL [[COPY]], [[COPY1]]
     ; CHECK: [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 63
     ; CHECK: [[ASHR:%[0-9]+]]:_(s64) = G_ASHR [[MUL]], [[C]](s64)
     ; CHECK: [[ICMP:%[0-9]+]]:_(s32) = G_ICMP intpred(ne), [[SMULH]](s64), [[ASHR]]
@@ -51,9 +51,9 @@
     ; CHECK-LABEL: name: test_umul_overflow
     ; CHECK: [[COPY:%[0-9]+]]:_(s64) = COPY $x0
     ; CHECK: [[COPY1:%[0-9]+]]:_(s64) = COPY $x1
-    ; CHECK: [[MUL:%[0-9]+]]:_(s64) = G_MUL [[COPY]], [[COPY1]]
     ; CHECK: [[UMULH:%[0-9]+]]:_(s64) = G_UMULH [[COPY]], [[COPY1]]
     ; CHECK: [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
+    ; CHECK: [[MUL:%[0-9]+]]:_(s64) = G_MUL [[COPY]], [[COPY1]]
     ; CHECK: [[ICMP:%[0-9]+]]:_(s32) = G_ICMP intpred(ne), [[UMULH]](s64), [[C]]
     ; CHECK: $x0 = COPY [[MUL]](s64)
     ; CHECK: [[COPY2:%[0-9]+]]:_(s32) = COPY [[ICMP]](s32)
@@ -91,3 +91,67 @@
     $q0 = COPY %2(<2 x s64>)
     RET_ReallyLR implicit $q0
 ...
+---
+name:            test_umulo_overflow_no_invalid_mir
+alignment:       4
+tracksRegLiveness: true
+liveins:
+  - { reg: '$x0' }
+  - { reg: '$x1' }
+  - { reg: '$x2' }
+frameInfo:
+  maxAlignment:    16
+stack:
+  - { id: 0, size: 8, alignment: 8 }
+  - { id: 1, size: 8, alignment: 8 }
+  - { id: 2, size: 16, alignment: 16 }
+  - { id: 3, size: 16, alignment: 8 }
+machineFunctionInfo: {}
+body:             |
+  bb.1:
+    liveins: $x0, $x1, $x2
+    ; Check that the overflow result doesn't generate incorrect MIR by using a G_CONSTANT 0
+    ; before it's been defined.
+    ; CHECK-LABEL: name: test_umulo_overflow_no_invalid_mir
+    ; CHECK: liveins: $x0, $x1, $x2
+    ; CHECK: [[COPY:%[0-9]+]]:_(p0) = COPY $x0
+    ; CHECK: [[COPY1:%[0-9]+]]:_(s64) = COPY $x1
+    ; CHECK: [[COPY2:%[0-9]+]]:_(s64) = COPY $x2
+    ; CHECK: [[FRAME_INDEX:%[0-9]+]]:_(p0) = G_FRAME_INDEX %stack.0
+    ; CHECK: [[FRAME_INDEX1:%[0-9]+]]:_(p0) = G_FRAME_INDEX %stack.1
+    ; CHECK: [[FRAME_INDEX2:%[0-9]+]]:_(p0) = G_FRAME_INDEX %stack.3
+    ; CHECK: G_STORE [[COPY2]](s64), [[FRAME_INDEX]](p0) :: (store 8)
+    ; CHECK: G_STORE [[COPY1]](s64), [[FRAME_INDEX1]](p0) :: (store 8)
+    ; CHECK: [[LOAD:%[0-9]+]]:_(s64) = G_LOAD [[FRAME_INDEX]](p0) :: (dereferenceable load 8)
+    ; CHECK: [[LOAD1:%[0-9]+]]:_(s64) = G_LOAD [[FRAME_INDEX1]](p0) :: (dereferenceable load 8)
+    ; CHECK: [[UMULH:%[0-9]+]]:_(s64) = G_UMULH [[LOAD]], [[LOAD1]]
+    ; CHECK: [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
+    ; CHECK: [[MUL:%[0-9]+]]:_(s64) = G_MUL [[LOAD]], [[LOAD1]]
+    ; CHECK: [[ICMP:%[0-9]+]]:_(s32) = G_ICMP intpred(ne), [[UMULH]](s64), [[C]]
+    ; CHECK: G_STORE [[C]](s64), [[FRAME_INDEX2]](p0) :: (store 8, align 1)
+    ; CHECK: [[C1:%[0-9]+]]:_(s64) = G_CONSTANT i64 1
+    ; CHECK: [[ANYEXT:%[0-9]+]]:_(s64) = G_ANYEXT [[ICMP]](s32)
+    ; CHECK: [[AND:%[0-9]+]]:_(s64) = G_AND [[ANYEXT]], [[C1]]
+    ; CHECK: $x0 = COPY [[MUL]](s64)
+    ; CHECK: $x1 = COPY [[AND]](s64)
+    ; CHECK: RET_ReallyLR implicit $x0
+    %0:_(p0) = COPY $x0
+    %1:_(s64) = COPY $x1
+    %2:_(s64) = COPY $x2
+    %25:_(s32) = G_CONSTANT i32 0
+    %3:_(p0) = G_FRAME_INDEX %stack.0
+    %4:_(p0) = G_FRAME_INDEX %stack.1
+    %6:_(p0) = G_FRAME_INDEX %stack.3
+    G_STORE %2(s64), %3(p0) :: (store 8)
+    G_STORE %1(s64), %4(p0) :: (store 8)
+    %7:_(s64) = G_LOAD %3(p0) :: (dereferenceable load 8)
+    %8:_(s64) = G_LOAD %4(p0) :: (dereferenceable load 8)
+    %9:_(s64), %10:_(s1) = G_UMULO %7, %8
+    %31:_(s64) = G_CONSTANT i64 0
+    G_STORE %31(s64), %6(p0) :: (store 8, align 1)
+    %16:_(s64) = G_ZEXT %10(s1)
+    $x0 = COPY %9(s64)
+    $x1 = COPY %16(s64)
+    RET_ReallyLR implicit $x0
+
+...
diff --git a/llvm/test/CodeGen/Mips/GlobalISel/legalizer/mul.mir b/llvm/test/CodeGen/Mips/GlobalISel/legalizer/mul.mir
--- a/llvm/test/CodeGen/Mips/GlobalISel/legalizer/mul.mir
+++ b/llvm/test/CodeGen/Mips/GlobalISel/legalizer/mul.mir
@@ -439,9 +439,9 @@
     ; MIPS32: [[COPY1:%[0-9]+]]:_(s32) = COPY $a1
     ; MIPS32: [[COPY2:%[0-9]+]]:_(p0) = COPY $a2
     ; MIPS32: [[COPY3:%[0-9]+]]:_(p0) = COPY $a3
-    ; MIPS32: [[MUL:%[0-9]+]]:_(s32) = G_MUL [[COPY]], [[COPY1]]
     ; MIPS32: [[UMULH:%[0-9]+]]:_(s32) = G_UMULH [[COPY]], [[COPY1]]
     ; MIPS32: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 0
+    ; MIPS32: [[MUL:%[0-9]+]]:_(s32) = G_MUL [[COPY]], [[COPY1]]
     ; MIPS32: [[ICMP:%[0-9]+]]:_(s32) = G_ICMP intpred(ne), [[UMULH]](s32), [[C]]
     ; MIPS32: [[C1:%[0-9]+]]:_(s32) = G_CONSTANT i32 1
     ; MIPS32: [[COPY4:%[0-9]+]]:_(s32) = COPY [[ICMP]](s32)
diff --git a/llvm/test/CodeGen/Mips/GlobalISel/llvm-ir/mul.ll b/llvm/test/CodeGen/Mips/GlobalISel/llvm-ir/mul.ll
--- a/llvm/test/CodeGen/Mips/GlobalISel/llvm-ir/mul.ll
+++ b/llvm/test/CodeGen/Mips/GlobalISel/llvm-ir/mul.ll
@@ -180,13 +180,13 @@
 define void @umul_with_overflow(i32 %lhs, i32 %rhs, i32* %pmul, i1* %pcarry_flag) {
 ; MIPS32-LABEL: umul_with_overflow:
 ; MIPS32:       # %bb.0:
-; MIPS32-NEXT:    mul $1, $4, $5
 ; MIPS32-NEXT:    multu $4, $5
-; MIPS32-NEXT:    mfhi $2
-; MIPS32-NEXT:    sltu $2, $zero, $2
-; MIPS32-NEXT:    andi $2, $2, 1
-; MIPS32-NEXT:    sb $2, 0($7)
-; MIPS32-NEXT:    sw $1, 0($6)
+; MIPS32-NEXT:    mfhi $1
+; MIPS32-NEXT:    mul $2, $4, $5
+; MIPS32-NEXT:    sltu $1, $zero, $1
+; MIPS32-NEXT:    andi $1, $1, 1
+; MIPS32-NEXT:    sb $1, 0($7)
+; MIPS32-NEXT:    sw $2, 0($6)
 ; MIPS32-NEXT:    jr $ra
 ; MIPS32-NEXT:    nop
   %res = call { i32, i1 } @llvm.umul.with.overflow.i32(i32 %lhs, i32 %rhs)